Glossary of Other Words

This is a reference page for words needing definition and not found in other organized glossaries on this site.

Rev.2003-03-01, -03-07, -08-17, 2004-01-15, -02-26, 2004-04-04
2005-01-08 Flat Glass, Sag Temp, -01-31 Fiber other, -04-12 Variac, -04-21 RFI, -06-23 Public Access,
 2005-08-21 Pneumatic, Hydraulic, -10-23 Lens, Microscope, Prism, Telescope, Optical Glass, Magnifying Glass
-11-28 Cire Perdue, Lost Wax, Cracking off, Overblown, Tooling -11-19 Amorphous, Super Cooled;
2006-01-20 Paste, Strass, Swarovski, -03-24 Misc., -04-12 Broad, Crown, Cylinder, -05-06 Soft, Hard, misc.,
-05-23 Pressed, -08-10 475 Marbles, -08-18 Cone, Contactor, -10-03 White Metal
2007-02-10 Glass, -05-23 Lazy Susan Bearing, -07-27 Leaded Glass, Copper Foil Work, Beveled Glass
-09-10 Strain image -10-04 Laminated, 11-14 Spectrum Link
2008-04-05 Plate Glass, Cast Glass, Flat Glass -05-21 Shop, Bit Boy, Servitor 
-07-16 Snow Globes, Snow Domes -12-05 Edits
2009-09-09, Tektite, Vitrified, Vitrified Sand, Volcanic Glass -11-14 Sugar Blowing, Sugar Glass
2010-08-18 format, -11-23 Poured Glass Jewelry, 2011-01-01 Bearing, -06-04 Edits
[Search on date pattern to find latest changes, more than one may be found.]

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Spectrum Glass Glossary


475 Marbles
475 marbles used to make Fiberglas and melted in early studio glass furnaces.Glass marbles that were the raw material for making Fiberglas. Significant because they were melted in the first efforts of making small glass melting furnaces at the beginning of the modern studio glass movement in the 60's 2006-08-10
AC Alternating Current
The power over the wires in the US and much of the world is alternating current - that is it increases and then decreases - 60 times a second in the US.  The advantage of such a system is that is easy to transform the voltage (the driving pressure) from the very high voltage used on long distance lines to the lower safer voltages used in homes and businesses - the higher voltage pushing more power through smaller wires than a lower voltage would.  The other kind of power is DC -Direct Current - which is more efficient, but which has been difficult to transform. ELECTRIC.HTM
Acid Cutback (ACB)
"A two layered art glass of contrasting colors that looks like cameo glass.  Process developed about 1906 by Carder at Steuben. Wax used for protection." Collectors Encycl.of Am.Art.Glass p225 Acid etch
A product that sticks things together cold; glue.  Modern high tech adhesives are available for almost invisible joints in glass strong enough to grind the glass after gluing.  Old fashioned hide glue is still used to make glue chip glass
A solid which has no crystalline structure.  Metals, most gemstones, and ice are all crystalline, their atoms or molecules line up in regular rows in the solid.  Glass is an amorphous solid. Physical properties So are most rocks in their gross structure although small bits may be crystalline. 2005-11-29  Wiki
Anneal, Annealing Temperature
When glass has been heated to a high enough temperature, it must be cooled by a controlled schedule of time and temperature or it will crack simply because of the strain inside the glass from the outside cooling faster than the inside. The sound of cracking glass in the waste buckets is common in glass studios. The thicker the glass, the longer the cooling time must be, days and weeks in the case of really thick castings. The annealing temperature can be determined by slowly heating a long thin piece of glass supported at the ends until it just starts to sag (the sag temperature) and the annealing temperature is taken to be 50°C (90°F) below that, usually about 900F (480C). When scientific measurements are possible, the annealing point is a specific viscosity.  "annealing point, AP—the temperature corresponding to a rate of elongation of 0.0136 cm/min when measured by ASTM Method C 336, Test for Annealing Point and Strain Point of Glass by Fiber Elongation. This test prescribes a rate of cooling of approximately 4 C/min with a fiber of approximately 0.065 cm in diameter, and a suspended load of 1000 g. The annealing point numerically approximates log = 13.0 poises, where internal stress is substantially relieved in a few minutes."
Art Glass
Usually refers to the glass produced in small studios starting in the early 1960's - the Modern Art Glass Movement. At its most extreme - glass produced by a single artist with limited assistance - it made it though the 70's, but expanded to include pieces produced by teams in the classic style, mostly because the leading exponent, Dale Chihuly, works that way. Pieces are normally unique although often similar in shape and/or color. Production Glass Art Glass also includes the decorative glass produced in the 30 years across 1900 when Tiffany and Gallé were active.
The appearance or actual fact of having equal weight on either side of a center.  A picture is said to be balanced if the amounts and tones of color on opposite sides of the painting, even though the color areas may be different and arranged differently.  Physical balance requires that actual weight on both sides of a pivot be equal, as in a whirly, although a heavy weight close to the pivot may be balanced by a lighter weight further from the pivot.  Static balance is the condition of not moving at rest - the most common example is putting weights on a scale until it rests level.  Dynamic balance is the condition of being in balance in all positions and therefore while moving - balancing a car wheel so that it does not vibrate while turning at 60 mph is one example.  It is possible to statically balance a wheel, flat on a pivot for example, and have it dynamically unbalanced because weight is on the inside rim and not on the outside, which is why most places spin balance a tire on a machine that tells where on each rim to add weights.  It is also possible to statically balance something on a horizontal axle but when the axle is tilted, say on a whirly or a dish antenna, it no longer is in balance because the center of gravity is out of line with the axle.  In a somewhat more complicated situation, a piece may change shape when moved, sagging across the mount and thus appearing balanced, but when moved, it returns to one or more specific positions.  An easy test for static balance of something that should go all the way around is to turn it to various positions and let go.  If it starts moving on its own, it is out of balance.  If it is in balance with a horizontal axle, it may shift when the axle is tilted because weight is in front or in back of the plane of rotation, but that was previously counter-acted by the forces on the axle. 2006-12-13
"Term used to describe glass which has been cut all over the surface with a series of short olive- or mitre-shaped lines, producing a matt striated effect resembling beaten metal." 20CFG [MF instead of lines, I would say indentations.]
Bearing, Ball Bearing, Bronze Bearing
A bearing is most often a cylinder surrounding a shaft to reduce friction on rotation of the shaft. Exceptions include sliding bearings and Lazy Susan Bearings.  The most common bearings in use are ball bearings and oilite bronze sleeve bearings. The first has two steel rings with hard steel balls captured in a groove between them; the actual profile of the rings depends on how much force along the shaft (thrust) the bearing must take and how much weight across the shaft. Different designs are used for relatively low speed and high speed  bearings. Even ordinary bearings can take a thrust like the weight of a flat grinding wheel.  Ball bearings must have shields to keep out dirt/grit/etc. or be sloppy enough to let it pass through. On this site, I have used them in my pipe shaper, whirlies and grinder. Also see threading
Oilite bronze bearings are hollow tubes of sintered bronze (heated bits of bronze pushed together just below melting point, leaving air space between them) that are fed oil or oil soaked for use.  They are used in cheaper tools, but my use of them is in slowly rotating situations, particularly the pulleys used as wheels on my equipment doors. 2011-01-01
Beveled Glass
When thicker glass is ground and polished at a shallow angle along the edges, it captures the light for an interesting effect.  Commonly done on thick mirror glass and solid door panels where it provides a visual frame, it is also done on much smaller pieces (bevels) that are fitted together to make designs.  Unlike stained glass where color and texture are major design factors, the glass is usually water white or has very light coloring, usually all the same color, and line and form are the design features.  Commercial flat glass firms can bevel large sheets and mirrors while specialized firms do standard and custom small shapes and groups that fit together.   2007-07-27
Bit Boy
In a factory shop, the person, often an apprentice or young boy, who collects and shapes gathers of glass for details like handles, feet and decorations for the gaffer or servitor to apply.  Also will take the finished piece to the lehr/annealer when done. 2008-05-21
"A broken surface bubble that leaves a pit mark" Collectors Encycl.of Am.Art.Glass p.225
an opening in the side of the furnace through which the pot is placed in the furnace; the batch is put into the pot, and the gather is taken. IGCB
Borosilicate Glass
A type of glass, Pyrex being one brand, with a low coefficient of expansion and high melting point, that withstands heating and cooling without cracking. Used in lampworking, telescope mirror making and cookware. The name comes from a high proportion of boron in the chemical mix and lack of soda and lime in the making.  Boro glass used in lampworking is now available in colors not previously available. Unlike soft glass, boro tends to not flow when heated.   MF
joining two metal objects by using material that melts above 840F so the material merges with with metal in the objects.  silver and brass are the most common braising metals.  soldering is lower temperature. also welding 2004-02-26
Broad glass (muff process)
window glass made from a blown cylinder. GLVAM; apparently an older process in which the hot glass is cut with shears rather than the later process where the colder glass is (scored? and)  cracked with a hot rod LCGCH Cylinder Crown
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Cameo Glass
Produced by first making a cased blank so layers of colored glass are available, then coldworking (wheel engraving, wheel carving, acid etching 20CFG ) to remove portions of the layers. Refers especially to white casing that is partially removed so the image resembles cameo portraits. MF
Cast Glass
May refer to three completely different processes.  Some stained window glass is made by pouring molten glass on a flat plate and rolling the result, thus cast glass, also used in old style plate glass.  Molten glass may also be scooped up in ladles or poured from tipping kilns into molds for making sculptures, tables, etc.  And molds may be heated in an annealer/kiln with cold glass placed in an upper reservoir where it flows into the mold when sufficient heat has been applied.  Crumbled glass may be packed in a mold and kiln cast in the process called pate de verre. 2008-04-05
"the glass-blower's bench, also a team working at a furnace" GLVAM so there may be several chairs at a furnace in a commercial setting. Only the gaffer occupies the chair.
The process of adding detail or ornament on metal by indenting with a hammer and tools without a cutting edge.
Uneven composition in glass, often barely visible as refractions of light or images in what should be uniformly clear. Often form when glass has been cooked for a long time in a pot without being drawn down and refilled. Will distort light paths in finished pieces and can be source of strain in glass that may cause breakage.
Lost Wax casting GL5K
A process in which wire are soldered to a metal backing and ground glass (enamel) is placed in the openings between the wire to create a design; the glass being melted flat into the space. A very detailed process, being more of metal working than glass. The metal may be gold, silver (and perhaps copper or brass, I am not sure.)
After glass has been annealed, it may require additional work to provide a cleaner product or to enhance the design. Painting is one way. All the operations that involve etching, engraving, grinding, cutting or polishing are considered coldworking. Non-decorative tasks include smoothing the edges of the punty mark, grinding the bottom flat for proper standing and signing the piece. Decorative methods include cutting and polishing. More
Coefficient of Expansion COE
Glass (and other materials) have a measurable rate of change in size as temperature increases. This is the Coefficient of Expansion (COE) and can be used to compare glasses for compatibility. Unfortunately, a measured or calculated COE is often for a low temperature, say 100 to 300, and the COE at 900 is different, so a compatibility test still has to be carried out. The COE can be measured or calculated from the quantities of ingredients. These often produce COE's that are quite different but still useful because they are consistent. Spruce Pine 87 is called that because its calculated COE is 87, while its tested/measured COE is 96. As long as one knows which is being used, things work out. Color
Incompatible fused glass piece showing strain cracksGlass expands with heating. Different glass formulas expand at different rates. If the difference is too great and the different glasses are bonded together, by fusing, furnace melting, torchwork or gluing, the materials may crack internally (right) or break apart, on their own (internal stress) or when heated (on a shelf in the sun) or chilled (in a car in winter.) A glass worker must be able to test for (or only use products tested for) compatibility. One test involves heating pieces of each of the glasses, melting them together and pulling a long strand with one glass on each side; the strand will bend on cooling if the glasses do not have the same rate of expansion. Another test involves fusing a small square (or several) of the glass to be tested onto a clear sample of the base or standard glass, annealing, and then testing in a polarizer. For more on these tests and comments about compatibility visit C.R. Loo  Color (207-09-10)
Cone, Orton Cones
A small clay device used for measuring firing progress in pottery work.  Available in steps of temperature and referred to as cone 5, cone 6, etc.  They are actually small skinny pyramids about 1-1.5" tall.  Usually from Orton Foundation, they were created to sag as the temperature approaches the correct point, but they take into account the time it takes to heat.  Usually 3 are used, ranging across the temperature desired and firing is considered complete when the lower temp cone sags to its tip touches the kiln shelf, the middle cone is bent about half way and the high temp cone has just started to bend.  In wood fired or massive pottery kilns, it may take hours or days to get up to final temperature, and the cones reflect the proper firing.  In an modern electric or gas kiln, it may be possible to take the temperature up so rapidly that the clay does not fire through and the cone should allow the temp to go higher.  Cones are also used in controllers where the sagging allows a trigger to trip and shut down the firing at the correct point.  Tables of cone temperature are available on the internet and I include a few in my temperature table. Orton Web Site 2006-08-18
A device for controlling power, usually like a normally open relay that is built to be closed (powered) for long periods of time and is used for high power connect-disconnect.  May be a coil and mechanical contacts like a relay or a connection made with a metal slug going into a pool of mercury; the first being noisier than the second when used for heating control. 2006-08-18
Copper Foil Work
A technique for stained glass (and some beveled glass) projects in which narrow copper foil is adhered to and wrapped around the edge of each glass piece and then the arranged pieces are connected by flowing solder over the copper to form the arched appearance of lead came or other effects.  Using different width foil permits more or less bold dividing lines and accommodates thick glass.  Developed in the late 19th century, copper foil was originally done with beeswax or other adhesive applied separately to thin copper cut from sheets.  Now coils perfectly cut foil have pre-applied adhesive under a pull off strip.  In the last part of the 20th century, the adhesive side of foil was colored black or silver so that when wrapped the shiny copper would not be seen through the edges of clear glass. Copper foil permits or eases work on designs with many small parts or curves or structures allowing more freedom in making boxes, lampshades, and sculptural designs. 2007-07-27
Core Formed
Before glass was blown, vessels were made by making a relatively heat proof core (from clay, dung, etc.) around which molten glass was threaded. The base coat might be made by rolling the core in crushed glass and melting it to form a surface. After the piece was made and annealed, the core was soaked and chipped out.
Costume Jewelry
Eisenberg Broach from internet siteJewelry in which the gems are made of glass "paste".  Goes in and out of fashion.  While I was growing up in the 50's, my mother owned several nice broaches by Eisenberg, each a couple of inches across. In 2006, Antiques Roadshow occasionally has large pieces of real gem jewelry that this is imitating and the owners report people saying "Why do you wear that tacky costume jewelry?" assuming it to be fake.  Good costume jewelry is bright and colorful with enough size to make a statement; it is thus out of style when understatement is considered the "In" thing. 2006-01-20
Cracking off
"A technique by which the rim of blown glass vessel is created: by using the point of a diamond and a trail of soft glass the vessel is separated from the overblow. Most frequently used on the making of thin walled vessels of those which have been blown in molds. [and thus no punty mark MF]" GL5K  In modern art work, more often used to refer to removal of the piece from the pipe or punty - cracking off. MF 2005-11-28
Crib Glass
Crib was a term originally used in connection with back yard glass makers who produced cheap variations of glass ware "under the counter" as it were undercutting wholesale prices and they paid no tax.  The term then went on the include all small productions and the first one was set up in 1867 by J. Harrop in Stourbridge.  They made small items and worked with cullet melted in small coke fired pots  Christine Bridge. (Ms.) 2005-08-17
Crown - flat glass method
A technique of making flat window lights (panes) by spinning out a large disk then cutting rectangles from the area near the rim, the center bulls-eye being used for cheaper lights and decoration. Method used circa 1330-1830. Broad Cylinder Window Light 2006-04-12
Highly technical term, like schmutz, used to name the stuff that is in or on the glass in the furnace that shouldn't be. It may be bubbly foam or white chemicals or stones left over from the melting process or coming from damage to the furnace or pot. Stones, chords, seeds
Cylinder - flat glass method
A technique of making flat glass for windows by blowing a long even cylinder, cutting the top and bottom domes off, and cracking a line up the side.  The cylinder is then reheated and manipulated to sag it flat and further annealed. Broad Crown Window Light 2006-04-11

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Dalle de verre (slab glass)
Flat slabs of colored glass usually set in concrete or epoxy resin for architectural work, produced in the US by Blenko Glass Company, Inc. shaped by chipping, etc. 2004-04-04
DC - Direct Current
Electric power in which the electrons always move in one direction in the wire (as opposed to Alternating Current) Chemical sources, like batteries, produce direct current, and it is needed for plating.  AC can be converted to DC with a rectifier; it is more difficult to make a well formed AC from DC.  DC is more efficient as a mover of power because the flow is even, instead of rising and falling above the nominal value, but harder to transform the voltage. ELECTRIC.HTM
Devitrify, Devitrification
When glass is heated, but is still not liquid, if it is held at that temperature for too long, as can normally happen only in a kiln during fusing or sagging, the glass-like qualities (vitreous) may be lost and the materials of the glass form a white crystalline crud on the surface (which may be "snail trails" for their pattern). Once formed it is basically impossible to remove. Solutions are available to spray on fusing projects which reduce the tendency of glass to do this, usually with boron to make a somewhat different glass at the surface.  Devitrification can also occur when glass is stored in a moist environment or with water inside or buried.  It is essentially impossible to recover from this damage.  2006-03-24
Type of glass and process. There are glasses, usually with colloidal gold in them, which have a distinctly different color in reflected or transmitted light. More recently a kind of glass that is distinctively colored with iridescence that changes with the light. This process involved depositing a thin layer of metal on the surface in a vacuum, which is moderately expensive. The glass is most often cut in small pieces and used as decorative detail in fused pieces. The film burns off at higher temps.
Elbow fittingIn plumbing a curved fitting used for abruptly changing the direction of a pipe. Elbows may allow a 45° or 90° turn. Sweep elbows have a smooth curve over several inches radius and are used with sewer line and electrical conduit. Most elbows have internal threads on both sides ('female') to accept the external threads on the pipe. A 'street elbow' has one external and one internal connection (male to female) and permits connection to a T or other fitting with internal threads without requiring a short nipple which would be longer than the thread on the fitting. A street L and a regular L together allow turning through other than 90° (example>) 2002-06  The middle joint of the arm of a human which is subject to damage if strained repeatedly (tennis elbow) as can happen in glass working. 2004-01
While most of us know of glossy enamel paint, the original enamel is ground glass, melted at 1000-1500F to form a glossy surface on metal. Copper enameling is placing powdered and lump glass on pieces of copper. Cloisonné is a kind of jewelry using enamel. Ground glass can be carried in a organic oil media (pine oil) to do painting; the oil setting to a rigid state and then burning off with heating while the enamel melts to the glass.
A form of coldworking that can take on several meanings, from using an acid etch cream to produce a mildly frosted look, to using sharp pointy tools to make little spots that texture an image on the glass, to abrasive blasting that can remove quite a bit of glass. 2005-03-16
Factory Glass
Factories for blowing glass manually are few and far between in the United States today. Steuben, Benko and Fenton are about all. In the 19th Century, all glass was made in factories, a team of workers producing the same piece at a rate of dozens per hour. Modern factories survive making more arty pieces for the mass market, including TV sales shows. On the team, one person does nothing but shape, another nothing but finish, another nothing but handles; the number of people on the team changes when a new piece is to be done. Studio
Fiber Glass, Fibreglas
Thin glass fibers used to make heating and electrical insulation and fire and heat resistant fabrics.  Molten glass is drained through platinum orifices, cooled quickly and twisted into yarn or tangled into puffy mat.  PPG Fiber Glass site 2005-01-31 Marbles from Johns Manville used to make fiber glass were a significant source of easy to melt glass in the early years of the modern glass movement.
Fiber Optic
Very thin glass (or plastic) strands with a core and coating(s) so that light inserted at one end almost totally reflects down the length and thus can be used for communications and remote lighting and observation.  Developed in the 1960's with availability of laser and solid state light sources now used by the thousands of miles for communications and for surgical examination through much smaller cuts in the body, not to mention miniature lighting effects. 2005-01-31
Fining, Fine the glass
Remove the bubbles from melted glass, also called squeezing and plaining the glass. Bubbles are introduced in the glass because it is made of particles with air between them and because glass chemistry gives off gas, 10% by weight of CO2 in some batch formulas. Some chemicals added to the glass, notably nitre (sodium nitrate) cause small bubbles to make big ones which rise more easily.  Small bubbles are removed by lowering the temperature from cooking temp (2400F) to below working temp, (1900F), which forces the bubbles into solution. 2005-02-09
Flat Glass
The Spring/Summer catalog of the Studio at Corning Museum of Glass is referring to Cold Glass as Flat Glass.  In this they are including painting on glass, stained glass, sandblasting, engraving, etc.  Since engraving and sandblasting are also used on round blown forms, it is somewhat misleading in my opinion. 2005-01-08  Flat glass also refers to window glass and leaded and copper foil work.
Unlike window glass, stained/colored glass does not have to be distortion free even when transparent.  Stained glass is made by many techniques - Spectrum has a tank furnace that overflows as a thin sheet which is spread into the annealer and cut at the end, Bullseye pours much of its glass and rolls the lump out on a flat steel plate.  Some companies pull the glass between steel rollers which may have a pattern on them. 2008-03-04
Float Glass
Modern high quality window glass is made by floating molten glass on a bath of molten tin (under nitrogen to keep from oxidizing the tin) and pulling a continuous sheet of flat glass off the other end. For a terrific description see PGMC Specifier's Guide The slight inclusion of tin affects people fusing with float. Before float glass (<1959), flat glass was either pulled up or drained down and that flat sheet was curved and pulled over rollers to anneal, with consequent distortions.  Before that (<1900) plate glass was cast and ground and polished and window glass was made by hand either by spinning roundels or by blowing cylinders (then flattened) from which panes/lights were cut. The Window Light Workers [Mod. 2004-01-15]
Floor Model
When piece ends up smashed on the floor, it is called a floor model. This most often happens at the moment when the glass is being parted from the pipe after attachment to the punty, but it can also occur if the punty gets too cold, releasing the glass, or when a glass piece is simply dropped.
fondi d'oro
'gold glass' Roman technique of gold leaf between two pieces made of glass which were then fused. GLSMI
Frit, Fritting
In modern usage, small pieces of broken glass, usually colored, commonly from grape nut size to grapefruit seed size (1-4 mm) used to add spots of color. Frit  In older days, the pre-cooked result of partial heating of the batch. Fritting Wiki-Frit
Fused, Fusing
The process of merging pieces of glass without (usually) taking them to complete melt. Done in a kiln, glass is raised in temperature until pieces or layers begin to melt, bonding to each other, but not so far that pieces change overall shape. Corners may round, and in extreme, pieces melt to flat. Because glass does not mix easily, various colored glass pieces may be fused into new panels or blocks, later to be sawn or cut to new shapes which are then fused or sagged to yet new forms. Warm Glass
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from old term for grandfather, the person leading the team who does the most critical steps of the working and coordinates the rest of the team. Title given to the person in charge of a piece even if others have more experience. Other people have titles like bit boy, bit gatherers, footers, handle makers, reheat boys, etc.
Both the name for going to the furnace to get glass (to gather, gathering) and for the glass gotten (first gather, second gather). The end of the pipe or punty is lowered into the glass and turned to drag the glass evenly around the pipe or previous gather. The analogy most often used for the process is turning a spoon or old fashioned wooden pickup in honey, keeping it turning to get to the plate. However, gathering glass involves stuff that is over 2000ºF that will melt and deform the previous gather if done too slowly (not to mention set clothes smoking.)
Somewhere on this site we need to define glass, I suppose, so here we go.  Glass is an amorphous solid made from sand and other ingredients. Solid of course means it is a clunky rocklike substance.  Amorphous means that it is non-crystalline.  Water is non-crystalline while ice is made up of crystals as are many rocks.  Because of this, some books try to say glass is like a liquid which leads some people to think it will flow at room temperature, given enough time. Nope.  The purposes of the other ingredients are varied - among the purposes are bringing the melt temperature down from that of quartz to something more reasonable, adjusting the behavior of the glass while working, and adjusting the color to water white or to add color or opaqueness.  When the ingredients are mixed, ready to be heated and melted, the result is called batch.  Cooking batch to make ready to blow glass takes several hours to overnight so most glass artists melt enough at one time to last for several days work, keeping the cooked glass liquid at a somewhat lower temperature overnight to save energy and reduce chemical decomposition. 2007-02-10 Wiki-Glass
Does anyone else find it odd that we have to define glassblowing? Especially since it often involves relatively little actual blowing. Unfortunately, there is confusion because the term is used for two totally different operations: Working glass at a torch and working glass from a furnace. The former is also called lampworking and torchworking and includes scientific glassblowing, neon tube working, and artistic tube and solid work.
The latter is also called off-hand glassblowing. This site is devoted to furnace glassblowing. Other forms of working glass hot are described under Warm Glass. Lampworking involves holding rods and tubes of glass, usually in the hands (or a lathe) and heating the other ends to do creative work, often small. Furnace working involves collecting molten glass melted in a high temp furnace and shaping it on the end of pipes and punties using tools that range from newspaper to high tech metals.
See Adhesive and glues.htm
Glue chip
Literally, glass textured by putting hot hide glue on the (lightly sanded) glass surface which tears chips of glass off as it cools, leaving a pattern somewhat like ferns or frost. Used in decorating with stained and beveled glass, especially when no color is wanted and when seeing through the glass is not wanted - entry side panels and bathroom windows or partitions. Most stained glass suppliers offer it; Carolina Glue Chip, North Wilkesboro, NC mentioned as a service source. If hide glue is used, it should be flake, not the prepared liquid type, and some woodworking supply places, including Garrison Wade, have it. A very good info source. 2002-07-17
In mechanized glassblowing, the glass produced is normally dispensed from a large tank furnace in the form of a hot blob of glass that drops into a mold where it is either blown or pressed. The industry name is a gob and the hardware is a gob dropper. MF
Gum tragacanth, Gum arabic
organic liquids made from saps of plants, species of Astragalus and Acacia respectively, which are are used in many ways to control the flowability of inks, dies, soaps, glazes, etc.  The primary use in glass work is gluing fused and pate de verre materials and making enamels flow. 2004-02-26 EB partly. Much cheaper to buy dry from ceramics places, but clearer and ready mixed from artist supply stores.
When a mirror is made without backing and with a thinner reflective coating it can be seen through when viewed from a dark room and will still look much like a mirror from a brightly lighted room. Some times called one-way glass which makes people think it can always be seen through from one side and is always mirror from the other - not true.  Mirror.htm
Hard Glass
Usually refers to borosilicate but also different soft glass hardnesses. See discussion at  Soft Glass
Hot Shop
Although sometimes used as a slang term for Studio, it most commonly refers to the physical area within a studio or glass factory where the melting and working of furnace glass occurs, in contrast to the Cold Shop or Cold Working area where grinding, carving, smoothing, etc., takes place. Other areas are Shipping, Storage, and often a Gallery or Sales Floor.

Run by liquids, oil or water, as opposed to pneumatic - run by air.  Uses in hot shop are limited because air tools move faster and any leaks are harmless air, while most hydraulic oils are flammable.  Most common uses are applying large forces with low effort - a 12 ton bottle jack is about the size of a quart milk bottle and will apply inexorable force with repeated light pumping of a short handle. 2005-08-21

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Inches (Pressure)
Shorthand for the difference in height of water or mercury in the sides of a manometer. Pressure
Investment (Foundry/Jewelry)
A white plaster like powder that is used in metal jewelry casting, withstanding high heat, but not very strong - must be held in a cylindrical form. Unlike plaster, when set it can be washed off the cast item, which is commonly done hot with metal.
An arrangement of 2 or 3 mirrors forming a tube viewed from one end which reflect the image or object at the other end multiple times, producing a radially symmetric image. Depending on the angle of the mirrors, the image may have 6, 8, 10, or 12 segments and will be different depending on how the 3rd mirror, if present, is placed. Common K's have 3 mirrors at 60° to each other. Front surface mirrors are used to avoid extra faint reflections inside. Much of the attraction of collectable K's comes from the form of the housing. There are several books and websites showing options Kaleidoscope Heaven and a discussion group added in 2005.
Kiln Wash
A thick liquid painted on kiln shelves and clay and steel molds to keep glass from adhering when fusing. The most commonly mentioned formula is 50% EPK Kaolin and 50% Alumina Hydrate mixed 1 part powder with 4-6 parts water to a desirable thickness (creamy) MAKING YOUR OWN MF uses Paragon Kiln kiln wash for the limited fusing that he does. Kiln wash must dry and is usually dusted with a finger tip to take off brush strokes and leave a slight loose coating. It should (I believe) be precooked before putting glass on it.
Kiln Working
Placing glass, usually cold, in a kiln and heating the glass to soften, melt, and otherwise form it. Warm Glass

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Laminated Glass
Flat glass with plastic between layers of glass.  Two glass layers and one plastic are used in automobile front windows to keep people inside the car and in making bullet resistant glass where there may be many layers of alternating glass and plastic. Tempered  2007-10-04
A form of glassblowing using a torch where the cold ends of glass tubing or rod are held in the hands or a glass lathe while the other ends are heated and melted together. An entire field to itself, including neon and scientific glass work, as well as bead making. More
Lathe, Glass Lathe
A tool most often used in scientific glassblowing which holds two pieces of tubing in line while heat is applied to fuse them end-to-end. More resembles a pipe cutting and threading machine than a machinist's or woodworker's lathe with the important proviso that the head and tail are both powered and synchronized so the two tubes turn together as they are heated.
Lazy Susan Bearing
A flat bearing used originally to make turntables in the middle of dining tables that hold condiments (or sundae makings) giving access to all diners while eliminating the maid (lazy Susan).  These are made of sheet metal with the bearing balls in a shaped groove between the sheets, usually with a large hole in the center, are quite cheap ($5-8 for 3-8" sizes) and hold remarkable weight - several hundred pounds even in the smallest sizes.  But they must be used flat (or at least with the force perpendicular), not being suitable for wheels of fortune or fans.  The unit is held together by bending the center flange over and when not flat, the flange drags - wearing through eventually.  Also, the bearing balls are exposed so dirt, sawdust, metal chips, etc. can get in easily.  I used one in my torch bottle cutting holder and index plate Showing bearing in more normal use. 2007-05-23
Leaded Glass
Glass pieces assembled with lead came which is soldered just at the connections.  Often thought of as stained glass which is colored, leaded glass also includes beveled glass which is usually water white and thicker, although it can be colored. Leaded glass was used in medieval cathedrals and is still used in modern work, although copper foil work dominates.  Leaded glass works best with straight lines or strong smooth curves as it forms a heavy dark line in the design.  Leading requires stretchers and cutters to accurately work with the came, which is H shaped when the glass is on both sides and U shaped along the edges, although zinc came is used for stiffness on the edges.  2007-07-27
If glass is given a curved surface, because of refraction when light passes from air to glass to air, the image viewed through the glass may be enlarged or reduced.  If the two surfaces are parallel as in bent sheet glass, little or no change occurs.  If one side is curved more than the other, a change occurs.  If the glass is thicker in the middle than at the edges, enlargement results; if thinner in the center, reduction.  Because glass can be had with different indexes of refraction, a precise lens, as in a camera or microscope, may be made up of several glass pieces so that all the colors come together in focus. For a camera, a normal lens is one that produces on the film an image like the one an eye sees, while a telephoto enlarges the scene in the image and a wide-angle reduces it, but includes wider detail than the eye normally sees.  2005-10-23
A satisfactory condition of glass for art glass working as the glass stays flexible as it cools over several hundred degrees. Steuben crystal is very long, Spruce Pine batch is considered long. Bottle glass is short
Lost Wax Casting
A method of glass and metal casting that involves making a model in wax, encasing the model in suitable investment material, melting out the wax and then pouring material into the cavity.  Permits undercuts and full round shaping not possible with techniques that involve pulling the model. GL5K 2005-11-28  Cire-perdue in French  While I have done metal lost wax, I have not done glass casting, thus there is no page on this site.
A portable enlarging viewing device usually with a fixed distance mount for the best enlargement with a simple lens arrangement.  Most commonly used in photography and printing where it is set down on the printed material for viewing of details which may be errors, but also used for a jeweler's loupe that is held against the eye to examine watches and jewelry for faults and flaws. Buying a Loupe 2005-10-23
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Magnifying Glass
A hand held mounted lens, normally a double convex for enlarging, used to examine small objects and print, the enlargement and focus being controlled by the hand positioning. Loupe 2005-10-23
A device for measuring pressure, especially the difference between two low pressures.  A U-shaped tube is partially filled with mercury or water and rigidly mounted before a scale, tilted for a longer display. The ends of tube are attached to the pressure to be measured and either the atmosphere or the other pressure.  2006-05-17
A mineral that splits to very thin translucent layers that withstand high temps.  Formerly used in stove windows and lamp shades and still used in toasters to support the element.  When broken up into flakes, reflects light and used in glass as decoration. Some mica sold is bonded with adhesives; natural mica can only take simple flat forms usually rectangular. 2003-03-07
A tool of science containing several lenses mounted in a tube with a precisely adjustable mount, often with a light source, for adjustable enlarged viewing of small samples.  A microscope enlarges the view, typically hundreds or thousands of times.  The sample may have to be sliced thin to transmit light.  The name has also been extended to devices which do not use lenses of glass, but use magnetic or static electric fields to focus electrons, x-rays, gamma rays, etc. to make images. 2005-10-23
Mirror, Mirroring
An object that forms a reflection of objects; the process of making such an object or surface. Mirrors have been made of metal, plastic and glass. Metal is usually just a polished surface. Plastic mirrors usually have metal in the the plastic material. Glass mirrors are made by depositing a thin metal layer on the front or back of the glass, most often silver or aluminum. Front surface mirrors are important in astronomy, security (half-silvered) and kaleidoscopes and are often fragile because of little protection for the silvering. Mirrors with the metal on the back are painted to protect the silvering and provide a sharper brighter image. Mirroring may be applied to the inside of objects to produce a silvery effect (Christmas ornaments, gazing balls) and to reflect heat (thermos) in a chemical process mirror.htm
the name for the blob of glass at the end of the pipe before it has enough done to it to call it the bowl, stem, or body or something else.
Natural Glass
Glass formed by natural forces including volcanic glass (obsidian, etc.), lightning glass (fulgurite)  and tektites probably from meteors. 2004-04-04
NPT National Pipe Thread
The acronym/name for American standard water pipe thread also used for gas. Sizes are nominal - that is the inside and outside diameters have nothing -today- to do with the designation. I assume the ID was once the designation and the pipe material was thick, so a 3/8" ID pipe (0.375) had a 0.675" OD or a 0.15 wall (over 1/8"). Today the material is stronger and the wall thinner, so the ID is bigger, but the outside remaining the same allows threaded connections to be interconnected. I have a Table of actual sizes on my plumbing page. Threading is tapered for a gas/water tight fitting. The same threading is used on lamp parts as a continuous thread. Pipe thread is a rather fine thread compared to bolts.  Nominal sizes are 1/8", 1/4", 3/8", 1/2", 3/4", 1" and on up.
A short piece of NPT pipe, usually bought already threaded, for making plumbing connections. A close [kloz] nipple is one that is so short the threads touch each other, so the fittings come close [klos] to touching, the length depending on the size of the pipe.
One Way Mirror or Glass
See Half-silvered and Mirror
Optical Glass
Glass which is specially prepared for clarity, exact composition and refraction, and lack of chords, to transmit light for making of lenses and prisms.  Also used for art projects where optical exactness is desirable.  When first created was melted in disposable crucibles and first melt was shattered and inspected to remelt purest pieces. 2005-10-23.
Overblow, overblown
In mold blown work, the top of the mold is aligned with the rim of the piece, so glass expands past the edge - it is overblown.  Cutting along the edge produces the rim of the piece without jacking and with minimal grinding. GL5K 2005-11-28
See discussion under reduction
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Painting, as connected to glass, is confused by various levels of technology. At the peak are enamels - ground glass - in a media which allows painting an image. When complete, the piece must be carefully fired to melt the enamel into place without distorting the piece. Very durable. In modern times, paints that are relatively transparent have been developed to allow painting glass to look like stained glass. These take two forms - plastics that set at room temperature and paints that require heating in an ordinary oven - less and more durable. Once upon a time silver compounds were used to make toned details (faces, etc.) on church glass which when fired made a dark brown image. Glass can be used as a carrier for a painting with ordinary paint, most spectacularly with reverse painting so the image is viewed through the glass. Flat glass can be used as a printing plate - paint or ink being applied and transferred to paper in a press.
Glass jewelry, costume jewelry.  Glass substitutes for real gems ("This is paste, the real stuff is in the vault.")  Material to make glass jewelry "specially prepared glass, known also as strass, from which imitation gems are manufactured. This latter must be the purest, most transparent and most highly refractive glass that can be prepared. These qualities are comprised in the highest degree in a flint glass of unusual density from the large percentage of lead it contains. Among various mixtures regarded as suitable for strass the following is an example: powdered quartz 300 parts, red lead 470, potash (purified by alcohol) 163, borax 22, and white arsenic 1 part by weight. Special precautions are taken in the melting. The finished colorless glass is used for imitation diamonds; and when employed to imitate colored precious stones the strass is melted up with various metallic oxides. Imitation gems are easily distinguished from real stones by their inferior hardness and by chemical tests; they may generally be detected by the comparatively warm sensation they communicate to the tongue." Encyclopaedia Britannica 11th Ed., Vol XX p. 890  Online 2006-01-20
Plate Glass
High quality window glass, now mostly made by the float method but originally made by pouring glass on a table and rolling it to make cast glass then grinding and polishing both sides to make the best possible glass of the time - and most expensive. 2008-04-05
Poise Pas Pascal
The measure of viscosity - Poise is old measure = 0.1 Pas under the standard metric measure.  Poise = dPas (deciPascal)
Polarizer, Polarascope
Two sheets of Polaroid (polarized thin plastic) film used to test glass (or plastic) for strain. When the two sheets are arranged properly, almost no light passes through both. Transparent glass placed between them will show areas of light and dark because glass under strain twists (changes the polarization of) light, more lines means more strain. Used to test for proper annealing and for glass compatibility. Also used in mechanical engineering where clear plastic models of structures show stress when pushed on.  On a less expensive level, the light of a clear blue sky is polarized which is why Polaroid sunglasses darken the sky around clouds.  Stressed glass will show dark bands when viewed against the sky through such glasses including the side windows on vehicles with tempered glass where they look like a dark net in the glass. 2007-09-04
Poured Glass Jewelry
poured glass jewelry exampleLumps of translucent glass with a flat back mounted in a metal collar.  In spite of the name, by several sources, it is made of pate de verre, glass paste, in molds and not poured.  As of the first entry date, I am still trying to find out how it got the name, which I never heard of before hitting a two page (156-57) spread in "20th Century Glass" Once discovered, many listings found on line. Image source 2010-11-23
Run by air pressure or flow, corresponding to hydraulic - run by liquids.  Most commonly applied to tools run by compressed air supplied by a motor driven compressor. In a glass shop, pneumatics may be doors lifted by cylinders, air blasts for cooling and cleaning, and high speed grinders. Small high speed chisels, grinders, and cutters are used in automobile work, larger jack hammers and lifts may be pneumatic.  Advantages are lighter weight (no metal electrical coils); even, applied pressure; no spillage if there is a leak of air; and no source of ignition around gasoline, etc. Filters, oilers, and water traps are normally required in the plumbing and pressure regulators may reduce the pressure conveniently. 2005-08-21
Pressed Glass
When a hot gather of glass is placed in a (usually metal) mold and a matching metal shape is forced down through it, the result is pressed glass, a major innovation in tableware of the 19th century as it allowed much cheaper production of glass that looked like cut glass. Pressed glass bits have been added to blown pieces for centuries: small medallions, feet, handles, etc., but semi-automation and later full automation of the gobbing and pressing made for cheaper glass. Pressed glass is usually not thin and since the pressor must be removed, is normally an open flared top like a bowl. Pressed pieces may be used as the basis for further work, like adding handles, etc. Pressing may be used to make molded bits to add to blown pieces. Variations include open mold blown, where a piece is mostly flat and the bubble of glass is blown onto a flat mold. Hudson Beach Glass, Beacon NY,; Mosser Glass, Cambridge, OH, "also engages private mold jobs" 2006-05-23 Pressed Glass Techniques
Prince Rupert's Drops
>> I have making these little things that i told are called "Prince Ruperts" drops. Just gather pretty hot glass and let it drip into pretty cold and deep water. These critters are shaped like tadpoles when cool. Hold it wrapped in a few layers of rags and with a pair of pliers break off the end of the tail. These things go off with quite an explosion and turn into dust. I know it has something to do with surface tension holding the thing together and not annealing properly. But exactly what is happening? Also the history must be interesting. Iv heard a couple theories but, does anyone REALLY know anything for sure about Prince Rupert drops ?>>
Yes, they are very well documented. You can make them in many sizes and generally are very predictable. With a polarascope you can see the stress lines. The strength in the body that allows hitting it with a hammer without shattering is the same strength that is in tempered glass used in car side windows (where you can see the stress lines with Polaroid glasses on a clear sunny day as a darker net of lines within the glass) but formed into a sphere that makes it even stronger. Impressive. If you make them big (1" or so) be very careful when breaking the tail off that they are tightly wrapped in cloth and tightly held. Do a Google Search to find a number of sites. This one has strain pictures
Glass cut so that light entering through one surface exits via another surface at an angle to the first, perhaps with internal reflection. Because refraction of the light differs by color to light is normally spread into a rainbow-like spectrum which may be used for decoration or for examining the light.  Three sided prisms are most common but in optical systems 4 and 5 sided prisms may be used to fold a light path making a smaller device and righting the image for convenience as in binoculars.  Cut glass uses the prism effect for glitter in hanging glass pieces and useful objects like bowls. 2005-10-23
Production Glass
Most glassblowing studios consider their output to fall in one of two categories: art pieces or production glass. The latter term has nothing to do with the mass production of bottles that involved most glassblowers of the 19th century, but describes the bread and butter pieces that they turn out to meet basic expenses of the operation. A common complaint is that they have lost the time to do art glass because of the need to do production glass or because of the success of their production glass. Production glass is relatively similar pieces - glasses, bowls, vases, perfume bottles, ornaments, goblets - that usually produce $20-50 income each and can be made quickly while still including what the artist considers signature handwork details. Many studios doing production glass go to wholesale art/craft shows.
PSI Pounds per Square Inch
Used to measure, in the American inch system, the force per unit area of gases and liquids. Unfortunately, it is not the only system used.  Heating gas in particular is often measured in "inches" meaning inches of difference in the height of a water manometer, 7 inches being common and being equal to 1/4 psi (28 inches=1 psi)  Occasionally, ounces per square inch will be encountered. Common psi measurements are atmospheric pressure (about 15 psi, varies), compressed air which may range from 5 or 10 psi for puffers to 70-120 psi coming out of a compressor.
Metric: 1 lb per square inch (PSI) = 6.9 kilopascal (kPa),  1 pascal = a force of 1 Newton per square meter; 14.7 psi = 1 atm[osphere] = 1 torr = 760 mm Mercury
Public Access Studio
One with a signup list for time slots to blow glass.  Unlike renting studio time, which is usually done in blocks of several hours or days by contract arranged in advance, whether in a private studio or class space, a public access studio remains available with glass being ready to use at any time and for shorter time slots.  Not all the time may be available in this form as classes and rentals may also be offered.  There are about six across the country, including Hot Soup in Philadelphia , Glass Axis in Ohio, Chicago Hot Glass, and Public Glass in San Francisco.  Usually, these places have membership, ways of earning blowing time by work effort, and a communal spirit that extends to fund raising, etc. Equipment must be rugged and there must be enough glassblowers around to get the work done. As with all high risk activities (amateur rodeo) there must be training and certification to be sure people signing up know what they are doing. 2005-06-23, 2011-06-04
Best known brand of borosilicate glass, invented by Corning Glass, which has a low coefficient of expansion (COE) so that when heated and cooled rapidly it does not crack. Thus it is used for clear glass cookware and for scientific and art lampworking. Melts at a higher temperature and remains stiffer than art or bottle glass and so requires special torches and eye protection. Used at fairs and carnivals for "knitting" figures of thin lines of glass specifically because it does not crack when cooling during working.  In recent years, many colors have become available.

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A crystalline mineral that can be used to make very high temperature (well over 3100F) clear tubing used frequently in solid state circuits manufacture.  Worked like glass with special torches and strong eye and skin protection. Properties
making bowl shapes from flat sheet metal by hammering around a center point and working out to the edge, which wrinkles the edge, which, when hammered down correctly, thickens at the edge  Sinkingrepousse.htm 2004-02-26
When a flame is rich in gas/fuel is said to be reducing or in reduction. (A flame or atmosphere rich in oxygen or short of fuel is said to be oxidizing, a less useful state in glass working.) Reduction is normally produced in furnace working by blocking the air flow into the blower (or adding extra fuel downstream of automatic controls) of the gloryhole. Reduction is useful in glass working because it changes some metal oxides to fine particles of the metal, producing a sheen or lustrous effect.  Gold, silver and tin compounds fumed or or glass containing them threaded on the glass will turn shiny metallic when heated and then the air to the glory hole is cut off (or gas added) so a yellow flaring atmosphere exists. The excess gas reduces (pulls oxygen from) the chemicals leaving pure metal which may be shiny in thicker places and iridescent in thin layers. 2006-05-06 revised.
The property of returning light back toward its source.  Something with a matt or dull finish will have a dull or no reflection and the energy of light will be mostly absorbed, usually raising the temperature.  The smoother the surface, the more precisely the light will be reflected, permitting an image to be seen/formed.  All reflection occurs at a surface with varying efficiency - some light passing through, some being reflected - depending on the relative optical characteristics.  Glass with a front surface of aluminum or silver makes a high efficiency mirror - used in telescopes - but very fragile.  Fiber optic transmission occurs because of reflection inside at the surface of two kinds of glass.  In a regular mirror, some light is reflected from the front surface, but most passes through the glass, with some loss, to reflect off the back, pass through the glass again to exit and overwhelm the brightness of the first surface reflection. 2003-03-09 A mirror with a smooth curve will enlarge or reduce the image, as seen in telescopes and car right side rear view mirrors. 2006-05-06
The property of light bending when it passes from one material to another with an different index of refraction.  The most common demonstration is a rod placed at an angle through the top surface of some water.  The rod appears bent at the surface because the light forming the image is bent passing from water to air.  Prisms and lenses depend on refraction, the focus or bending of light occurring twice, once when the light passes from air to glass and again when it leaves from glass to air, being bent in the same direction each time due to the angles of the surfaces with different colors being bent different amounts.  Cut crystal gets its brilliance from reflection and refraction of light, a source being broken up into multiple returning rays. 2003-03-09
shaping sheet metal, usually silver, gold, brass or copper, by hammering on the back with shaped punches with the metal backed by pitch either in a bowl. repousse.htm Could be used as a method of making glass molds. 2004-02-26
RFI Radio Frequency Interference
When electrical and electronic devices operate, they may produce spikes of power which result in radiation at radio frequencies.  Depending on the power of the spikes and the sensitivity of the receiver these may result in noise being heard on PA systems, radios and cordless phones, interference in functioning of remote controls and in extreme cases of damage to equipment.  Welding machines produce RFI as do contactors opening and closing and solid state relays or SCR's in phase control may if not properly designed to avoid it. 2005-04-21
Sag Temperature
A measured characteristic of glass, defined as when the glass viscosity is 7.6 dPas which is practically measured by supporting a thin rod in a kiln and raising the temperature in steps until the rod just sags of its own weight within 5 minutes.  Most texts report supporting the rod at both ends; Halem says it is supported at one end (with bricks on top) and waiting up to half an hour. For official, see Softening Point 2005-01-07
Sagged, Sagging
When unsupported glass is heated, it first begins to bend from its own weight then (at a higher temp) lose its shape, finally flowing and merging to a fused mass. Since this change usually occurs over several hundred degrees (F), it is possible to watch the process and control it for artistic purposes. A common art glass will begin to move slowly at about 1200F, be soft and floppy about 1300F, begin to fuse at about 1400F and fuse flat at 1500F. Artists take advantage of this range by "dropping" the glass into molds or through rings to form bowls and other shapes. Kiln Worked or Warm Glass
SCR Silicon Controlled Rectifier
An On-Off switch that is controlled by a control voltage.  Once the switch is on, it stays on until the power current and voltage pass through zero, thus it is almost always used for AC power which shuts off 120 times per second.  To control AC power completely, two SCR's back to back or a Triac must be used.  Control  Electrical
Small bubbles in the glass, sometimes desirable, usually not. When glass has these bubbles it is said to be seedy. Seeds are normally removed by lowering the temperature of the molten glass to drive the bubbles back into solution in the glass. Tested by making a small gather and looking at the glass.  Bubbles may be driven off by blowing compressed air into the bottom of the molten glass or by holding a damp vegetable or fruit, commonly a potato, below the surface.
"The main assistant to the gaffer" Collectors Encycl.of Am.Art.Glass p226 2008-05-21
Glass with a short working time because the change in viscosity is large with a change in temperature, so the glass goes from fluid to stiff quickly as the glass cools a few hundred degrees. Useful in bottle glass for getting the bottle out of the mold. Long
1. In a factory, "A collective term designating the crew that produces a completed glass object" Collectors Encycl.of Am.Art.Glass p226 MF: which consists of a variable number of people depending on the object - a gaffer, a servitor, one or more bit boys, maybe people pressing a base, etc. 2008-05-21
2. Rather obviously, a retail shop that sells anything including glass.  Perhaps less "pure" than a gallery that shows only art items with no jewelry, glassware, etc. 2008-05-21
One of the most common elements on earth and a major component of glass as silicon dioxide.  Part of quartz, granite, sand, etc.  Used in high purity form for making integrated circuits. 2007-05-27
Inorganic-organic polymers used in adhesives and many other substances including the filler for breast implants. Wiki 2007-05-27
making a bowl shape from flat sheet metal by hammering from the rim into the center, usually against a soft surface or depression. As normally done, the center is thinner than the rim which is near the thickness of the original metal. Raising. repousse.htm 2004-02-26
Slab glass
See Dalle de verre
Mostly the same as sagging, with the possible proviso that sagging is sometimes limited to work done into a mold while slumping is more narrowly the heating of unsupported glass, so glass may be slumped through a ring (drop out mold) or over a stainless steel form. warmglas.htm
Snow Globes
Snow Domes
Hollow glass or plastic balls or hemispheres on a wood or plastic base with scenes inside in plastic or plaster with water and small particles that float when the unit is shaken or whirled, most often with white material representing snow although colored has been used. 2008-07-16
Soft Glass
Soda Lime glass, the ordinary stuff of art, bottle, tableware and window glass in contrast to Borosilicate used for scientific glassware and cooking pots. But also used within soft glass, especially multicolored stained glass and fusing sheets because different chemicals used for different colors produce different cutting characteristics.  Thus an even pull with the cutter will produce a fine thin scratch on harder areas and a deeper scratch on softer areas, the thin scratch possibly not breaking cleanly. 2006-05-06
Softening Point
the temperature at which glass has a viscosity of 10 7.6 poises. In this temperature range glass will deform noticeably under its own weight: ASTM C 338. "softening point, SP—the temperature at which a uniform fiber, 0.55 to 0.75 mm in diameter and 235 mm in length, elongates under its own weight at a rate of 1 mm/min when the upper 100 mm of its length is heated in the manner prescribed in ASTM Method C338. Test for Softening Point of Glass at a rate of approximately 5 C/min. For glass of density near 2.5,  this temperature corresponds to a viscosity of 10 7.6 poises. "
joining metal objects by heating below 800F and applying a metal solder which may contain tin, lead, bismuth, silver in various combinations to control melting point.  True silver soldering is braising. also welding
Spruce Pine batch
A brand of batch glass mix that was developed early in the modern art glass movement and which has dominated the market from a smallish operation in Spruce Pine, North Carolina, because of its good working characteristics, clarity, convenient bagged packaging, and pelletized form which keeps unsafe dust reduced in the studio. 2005-02-10
Spun Glass
Image of ship made with spun glass techniquesGlass figures made from Pyrex type glass that look as though they were knitted or stitched using glass.  A variation of lampworking that gets little respect because it is so often done to make cheap junk at carnivals, fairs and boardwalk vendors.  Can be used to make fragile pieces with true artistry but is rarely seen that way. 2004-04-19
The process of taking bubbles out of molten glass by changing temperature, see Fining
SSR Solid State Relay
A device for controlling electricity that has no moving parts, using the solid state device a SCR or Triac to control power in an On/Off manner..  More info
Stained Glass
Colored glass, also the craft of working colored glass cold into patterns and objects using lead came or copper foil with solder to hold it together. The glass can also be used, when tested for compatibility, in warm and hot glass working. Normally delivered in flat sheets made by casting or pouring. Originally, the term comes from using silver compounds in solution to draw on glass used in cathedral windows, when the glass is heated, the silver bonds with the glass producing a permanent medium brown image - for example the details of the face when the head, body, and robing outlines are formed by the lead lines.. Leaded Glass 2007-07-27
Small objects in the molten (or finished) glass that look like stones and really are bits of crucible or furnace that were picked up during working or pieces of batch that did not melt.
Strain Point
Temperature/Viscosity point at which annealing is done because no further strain relief will be done in any reasonable time. Viscosity
Originally a name for paste the glass material of costume jewelry, converted to brand name in 1977 by Swarovski per their site. 2006-01-20
A facility for blowing glass, usually involving a single artist or team (one or two benches) in contrast to a Factory - which is artistically considered an insulting term. Studio normally includes all the activities of creating glass objects.
Sugar Blowing, Blown Sugar
If sugar is dissolved in boiling water and heated a lot with processing (see Web ref. or Google 'blown sugar') including adding corn syrup and cream of tartar to a temperature of over 300F, then cooling and pulling, a mass of "sugar glass" exists which can be used for blowing or shaping in to confectionary shapes or practicing glass blowing. The cooking/working process is tedious and the hot sugar dangerously hot and sticky.  2009-11-14
Sugar Glass
When, in the movies, people are hit over the head with a glass bottle or thrown through a glass window, the transparent stuff that is breaking is not glass or plastic but is a thin layer of hard sugar.  The bottles are fairly expensive because they are difficult to make and ship being fragile.  The flat glass can be made at home, but like any sugar product absorbs moisture and gets sticky and the view through it is not very good. (In the movies, when a window is looked through then broken by a person, the window is replaced with the sugar glass and the film edited to change view between the clear shot and the crash.) Google 'sugar glass' and 'breakaway glass bottles' for links 2009-11-14
Refers to liquids that are chilled below their freezing point but are still liquid, usually freezing instantly if disturbed or a crystal is added - for discussion of misuse in connection with glass go here
Brand of high quality lead crystal glass ornaments and accessories.  Best known for drops and other pieces used on chandeliers.  Originally founded to make lead crystal for paste gems, circa 1910.  Site 2006-01-20
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A glassy material produced by the heat of the force of a meteor hitting the earth. There several large spray patterns from large meteors hitting the earth and remains of many smaller ones exist.  There is even a mine of moldavite which led to the tektite name and origin suggestion. 2009-09-09 Wiki-tektite
A device for viewing enlarged images of distant objects.  Enlargement may be done with lenses or curved mirrors which are normally mounted in tubes which also hold an eyepiece to focus the image.  Telescopes may range from tubes a foot or so in length to elaborate mechanisms weighing hundreds of tonnes housed in buildings to protect them from the weather and hold additional instruments to examine the light collected for the image.  By extension, the name is also used for other devices that use radio, x-ray, and gamma rays which are sensed in patterns to form images of distant galaxies. A telephoto lens is a long multi-sectional lens for a camera that is carefully built for the best images. 2005-10-25
Tempering, Tempered Glass
If a sheet of glass is blast chilled with cold air from the annealing point, the surface contracts over the interior and forms a high strain glass that is more resistant to breaking from light blows, and this is called tempered glass, which is required in architectural installations (shower doors, glass entry doors and door surrounds) because when it does break, it does not form sharp shards, but small curved edge pieces (and tiny splinters.) The areas of glittering glass bits seen in the street where a vandal has broken a car window are tempered glass fragments. (Laminated) [MF I have collected these and fused in bowl shapes.
 Tempered glass is usually identified with an etched trademark in one corner. With Polaroid sunglasses against the polarized clear sky (or a polarizer), tempered glass appears to have a dark net of lines running through it as the strain pattern is revealed. If the surface of tempered glass is broken with a sharp point or scratch, the whole shatters.  For this reason, it is not normally used for shelves which get scratched in used or banged and chipped and where this mode of failure would drop all the objects on the shelf to the floor or the next shelf. 2008-12-15
Acronym for Things I Learned.  Used in Hot Glass Bits print version first.  Miscellaneous small items learned in process of doing things. 2006-02-02 Link to accumulation page
Shaping the soft glass by squeezing or pressing with jacks or other tools.  GL5K 2005-11-28
A solid state device for controlling AC power that behaves like two SCR's back to back.  Two SCR's normally allow control of more power while a triac is more convenient.  Switching can be merely on/off or phase controlled for fine control.
Plumbing joining device. When pipes are joined with considerable elbows and connections, at some point in the path it is desirable or required to have a union which is basically a joint made with a nut not rigidly attached to the pipe so that without twisting the pipe, the joint can be undone.  Without a union, most even slightly complicated plumbing setups would have to be disassembled from the end to repair a leaking fitting.  If allowed by code, a flare nut copper connection can be used as a union.
Uranium GlassUranium glass examples
Uranium oxide can be used to color glass, producing a product also called vaseline glass due to the color shared with the product. The uranium can be radioactive but does not have to be.  The glassware glows in black light and the glassware has an odd sheen in daylight. which contains danger comments and other images .
Variac Variable Transformer
An adjustable transformer capable of 5-20 amps that had great use before solid state electronics came along.  Used in early art glass annealer controls.  Heavy and expensive for the capacity due to copper coils inside. Modest sizes available surplus. 2005-04-12
Vaseline glass
see Uranium Glass
A measure of the thickness or flow rate of a liquid. Normally viscosity changes with temperature, getting lower as the liquid flows more easily at higher temperatures.  In the case of glass mixtures, the viscosity changes from very fluid to very stiff over different temperature ranges depending on the composition of the glass. Art glass is said to be long because it stays workable for some time while cooling (say over 300F degrees) while bottle glass is said to be short because it stiffens up over a narrow range (maybe 100F.) Viscosity is not the same as density which is the mass per cubic volume. A liquid, like mercury, can be very dense (heavy) while having low viscosity (flow easily.)  Motor oil is less dense than water (will float on it) but is more viscous and 50 weight oil is more viscous than 30 while 10W40 maintains about the same viscosity from cold to hot.
While most solids go from solid to liquid over a few degrees or at a specific melting point and the liquid may have changing viscosity, glass can be very stiff but moveable hundreds of degrees below the point at which it is a drippy liquid.
Schott, p.19, gives specific numbers for glass viscosity. Glass must be at 102 Poise to cook to homogenous state (the same as olive oil at 20°C/68F) The state from 104 to 108 P is the working range, 107.6 P is the softening point at which it will sag of its own weight, 1013 is the annealing point and 1014.5 the strain point.  The temperature change from the annealing point to strain point may be small (100F boro or window glass) or larger (300F Spruce Pine)
Glass sometimes described as being more like a liquid than other solids and this has led to some some absurd speculation (cathedral windows are thicker at the bottom because "liquid" glass sagged over the years) but the viscosity of glass at 800F is so great glass will break if dropped and it increases from there, so that glass is an unchangeable solid at room temp. If glass is not a liquid, what are the correct terms? Organized solids are crystalline, while non-organized solids are amorphous. Glass is an amorphous solid.
Longer List
Material Viscosities °C °F

Water (68F, 20C)

0.010 poise (metric dPascal dPas) 1 cP 20  
SAE 30 Wt oil 1.0 poise    
70% Sucrose in water 4.80 poises    
Honey (17.1% water, 25°C) 68 poises (varies wildly with temp & moisture) 25  
Glass cooking 102 poise   2350
Olive Oil (20C/68F) 102 (100) poises 20  
Soft end of glass working range 104 (10,000) poises   1800
Glass Softening Point (sags of own weight) 107.6                  (39,810,717) poises   1050
Firm end of glass working range 108                  (100,000,000) poises   1000
Pitch (famous experiment) 2x109 (about one drop every 8 years)   70
Glass Annealing point 1013     (10,000,000,000,000) poises   890
Glass Strain Point (low end of annealing process) 1014.5 (316,227,766,016,838) poises   700
From CMOG site: "Softening point: the temperature at which a glass fiber less than one millimeter in diameter will stretch under its own weight at a rate of one millimeter per minute when suspended vertically. This occurs at a viscosity of 107.6 poises."  [Normal test given is to cut a long flat cut of glass or rod supported at the ends, starting at temp below soften, raising temp in 5 degree steps and holding for 5 minutes, repeating if no sag.]
Oil viscosity is measured in centiStokes which is poises divided by density (in gram per cc) (so 1 cSt=1 mm^2/s)
A really nice site with detailed information on viscosity and a table of viscosities of materials:. Viscosity 2006-11-06 Wiki multipoint discussion 2010-12-08
Glass is an inorganic product of fusion that has cooled to a rigid condition without crystallizing and, therefore, has no melting point as such. There are, however, four temperatures that are of interest to the glassblower. They are:
1. The Working Point — the temperature at which glass has a viscosity of 10 4 poises. At this temperature, glass is soft enough for most lampworking or sealing operations. (Thick honey or molasses)
2. The Softening Point — the temperature at which glass has a viscosity of 10 7.6 poises. In this temperature range glass will deform noticeably under its own weight: ASTM C 338.
3. The Annealing Point — the temperature at which the internal stress caused by rapid cooling from lampworking or forming temperatures may be substantially removed in a matter of minutes. It is determined by measuring the elongation rate versus temperature of a fiber of glass under conditions prescribed by ASTM Designation C 336.
4. The Strain Point — the temperature at which the internal strain in a glass is substantially relieved only after a matter of hours and not at a commercially desirable rate. It is determined by extrapolation of annealing point data for fiber elongation: ASTM C 336. pdfs/physical_properties_glass.pdf  
Rather too often one sees a reference that glass is a super-cooled liquid as an awkward way of saying is is non-crystalline or amorphous solid.  This is unfortunate because the correct use of the term should refer to liquids that are cooled below their freezing point and remain liquids.  Typically, these will freeze across almost instantly if disturbed or if a crystal of the solid is added.  Pure water can be super-cooled down to 27-28F without freezing. 2005-11-29 More discussion of glass as
Made to form a glassy substance by heating.  Making a glass or glaze.  also Vitrification and Devitrification 2009-09-09 Wiki-Devitrification
Vitrified Sand
Sand that has been melted by lightning or meteor strikes or by nuclear blasts.  2009-09-09 Wiki-Vitrified Sand
Volcanic Glass
 Material that has been melted to molten in volcanic magma and cooled rapidly to form non-crystalline glass materials. 2009-09-09 Wiki-Volcanic Glass
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Warm Glass
Since the late 1990's, the working of glass has been divided into Cold, Warm, and Hot Glass, mostly by people doing Warm Glass to mark out their own activity. Warm Glass is normally done in an electric kiln, where the glass is placed cold and heated, either for the purpose of fusing pieces into a decorative arrangement or to sag the (perhaps previously fused) piece into or across a mold. A Very Good Warm Glass Site ( My warm glass. The Spring/Summer catalog of the Studio at Corning Museum of Glass is calling Cold Glass as Flat Glass. 2005-01-08
joining two objects, usually metal, but also glass, by melting the materials until they merge. Soldering, Braising 2004-02-26 Also used with plastics where a solvent is used to soften the plastic - solvent welding.
White Metal
Clear uncolored glass.  (Also, zinc based casting metals)   The term is an old one to cope with the fact that colored glass can be transparent - "clear".   White opaque colored glass is described with other words, like opal or milk glass.  In the glass industry in the days of hand blowing for production, the glass is called metal. 2006-10-03
Window Glass
Relatively flat clear glass used for letting in light and keeping out weather. See discussions at Float Glass, Flat Glass, Plate Glass
May refer to either the cold working or hot working characteristics of glass. Soft stained glass is easy to cut (workable) while hard or uneven glass is difficult to cut without cracks running off the line (low workability or unworkable or hard to work.) When talking of hot glass, usually the range of acceptable viscosity is meant.
Working Point
the temperature at which glass has a viscosity of 10 4 poises. At this temperature, glass is soft enough for most lampworking or sealing operations. pdfs/physical_properties_glass.pdf


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