Hot Glass Bits #38

Contact Mike Firth

November 1, 1997- June 1, 1998

Prev.Issue 37 Link to HGB Table of Contents Next Issue 39


2 ND EDITION - In article , Tom Craft writes:
>Sant'Agata wrote:
>> Where can I find out about the technique, equipment and materials to learn
>> this craft? Any informative books or web pages to recommend? Also, would
>> like to have info on catalogs that carry what I need to get started. 800
>> numbers?
>> TIA, Frank

I have just received a courtesy copy of the new second edition of Contemporary Lampworking by Bandhu Scott Dunham [Salusa Glassworks, Box 2354, Prescott AZ 86302 and also available at glass focused bookstores and by special order from Barnes and Noble I saw on their web site, ISBN 0-9658972-0-6]
I said publicly that the first edition was good and this one is bigger and better.
This is a book that has got to be owned by anyone who has the slightest interest in lampworking (and almost anyone who is interested in what a really good craft book should look like.)
The book is filled with pictures of glass by many different current lampworkers and of people working glass and is filled with technical information about glass and drawings of how glass should be worked. And not a few philosophical quotes.
It is 336 pages long with seven appendices - including a good look at physical safety while working glass and the risks of the chemicals involved in glass.
Even with all those pages, the center of the book has about 25 unnumbered pages with 76 color pictures of modern lampworked glass.
Chapter and major topic titles include: Origins of Lampworking, Understanding Glass, Setting up a Lampworking Studio, Basic Rod Techniques, Basic Tubing Techniques (Small and Large), Advanced Techniques, Working with Color, Beads, Jewelry and Marbles, Lampwork Crossover, Latheworking, Annealing, and Thoughts. Appendices include Further Study, Suppliers, Technical Info, Photographing your Work, Health and Safety Hazards, and care of the body. 11/11/97

>>I hope you will pardon me for butting in here, however I have a problem that is in your line of work. I have a friend that is frit casting 24%Lennox crystal and she cannot get any information that relates to things like temperatures, annealing, casting tips etc. The supplier that sold her the material is a reputable well-known glass artist but will not give out one bit of information. I would appreciate any input.

Selling glass without the information is dumb.

To determine the annealing temperature (roughly) do the following - take a long thin piece of glass, say 8 inches by 1/8" or so. If none of the crystal is available in this form, then fuse up a piece and over anneal it (take it down very slowly.) Support the long thin piece of glass between two support and slowly raise the temperature. (Of course, it is easier with several pieces, using the first piece to get a rough idea where it softens by raising the temp 50F a minute. Then the second piece can be raised rather quickly to 150F below the sag and continue as follows.) Raising the temperature 5F at a step, with a pause to check the glass, find when the piece just starts to bend. The upper annealing point is 50F below this.

After casting the glass (see below) the kiln is brought as quickly as possible to the annealing point (open the lid.) It is held at this point for at least an hour and longer per various tables as the glass gets thicker. Then the temp is lowered slowly to avoid setting new strains, to the strain point. For glass up to about an inch thick, holding for one hour per 1/4" and dropping 300F over 8 hours should be more than enough. If the controller allows it, spending more time at higher temps is nice (like if the annealing point is 900F, then instead of going down about 40F per hour evenly, drop 20F for the first hour, 25F for the second, 30F for the third and so on.

The casting temp can best be determined by laying out some glass on a kiln shelf and using a reasonably good thermometer (pyrometer, controller) to observe the various changes in the glass, what temperature it sags, when it slumps into a form, when it flattens into a puddle, when the puddle begins to spread. 11/8/97

Nice phone call from Terry Maxwell, upon receipt of Hot Glass Bits announcing its closing down. 11/8/97

GLASS announcement about shutting down 11/11/97 8:42 PM I recently sent out issue #37 of Hot Glass Bits and in it I announced that I was suspending publication. I have returned uncashed any checks laying around and have written special notes to those with balances to their subscriptions. Back issues are still available at $20 a set.
As I explained in the issue, due to changed circumstances in the rest of my life, I am unable to travel easily to see nearby glassworks and have too little time to do expeditions, so I have less to share. I also have so little time away from work that I would rather finish rebuilding my equipment and get hot again.
I will organize what I have into some form, work here on and maybe enhance my web site with more info. If anyone out there thinks they have some money due, let me know via e-mail or land mail. I have talked by phone with one person about a check I am certain is around here somewhere.

In article , (Mev5) writes:
>Does anyone out there have any experience with convincing the beaurocrats
>that they aren't necessary on a glory hole? Is there a less expensive
>device out there that could be installed in the gas line (we are using
>natural gas) that would satisfy them? Any suggestions would be appreciated.
The code people in Houston accepted a suggestion I made to people down there which I borrowed from a studio in Wimberley Texas.
Instead of monitoring the flame in the glory hole with an expensive purple peeper (which is used, for those who don't know to detect flame failure by looking at the UV) monitor the flow of gas outside the glory hole with a pilot flame, just like and using almost the same equipment as on a home heater.
That is, have a small gas line from the main line heat a thermocouple, use the results from the thermocouple to keep a valve open. If the gas pressure drops so much the flame goes out, the valve shuts and stays shut.
This can also be used on a furnace if gas pressure losses are rare and you are willing to lose the pot with the frozen glass, since one of the purposes of the purple peeper and associate circuitry is to decide whether to turn the furnace back on, and this just shuts it off.
Because of the high rate of flow, you will (probably) not be able to use standard parts. W.W. Grainger has a variety of valves and thermocouples.

From my notes This could be done with a Thermocouple Pilot Switch (Grainger 2E231, p.2454, $39.05) and a Solonoid Valve (2E228 p.2455, $72.15) which may be required if using LP Gas or extra large Btu. [Also required is a thermocouple (get the longest, 48", 2E337, $4.95), a bracket to hold the thermocouple in a flame, and suitable piping for the flame.] But fewer complications, lower cost and electrical safety are added less expensively with a Combination Valve (4E096, p2456, $75.60) for natural gas only. The valve comes with the tubing, 750 mv thermocouple, etc., and is self-contained, requiring no power. To add power protection, we run a wire from the power safety relay to the Valve. This wire replaces the thermostat connection so the valve is always on when the power is on.


Date: 97-11-15 07:11:21 EST From: (bert weiss) To: (MikeFirth)

Here in Portland My friend Chris Heilman Has a setup just a little different than Mike describes. He has an electric blower and natural gas. He uses a shut off that turns every thing off in the event of A power failure like you described. However after losing numerous pots, he added an uninterruptable power supply. Most of the power outages around here only last for a few seconds.

Previously this would shut down the furnace, but now the power supply kicks in and everything stays running until the power returns. If anyone is interested I can find out the specs and cost of the power supply. I'm sure it is worth whatever it costs. >>

Go for it. UPS costs have come way down with their popularity for computers and the blowers for glass furnaces would not require a very big one although a good sine wave form would be nicer for the motor. An alternative would be a 12 volt blower (from a car?), a battery, and a 12 volt charger/power supply that would keep going on a failure. But not nearly as easy to set up.

There are currently 144 images of glasswork on ! Go to and enjoy them. If you just leave your web browser connected, the slides will change automatically every 30 seconds. After you've been through them once, they'll load very quickly. More are added on an ongoing basis, so be sure to bookmark it. Albert Lewis 11/16/97

NORTH AMERICAN GLASS 1998 - Application Deadline 1998 Jan 15 - This is a hot, warm and cold glass show running from May 24 to July 18. Awards of $1,000, $500, and $250 will be given based on slides submitted to Juror, Suzanne Greening, Director, International Glass Museum. Up to three works may be submitted in the form of one slide each (although an additional detail slide may be included.) Jury fee is $20. For an application with full rules about delivery, pickup, commission on sales, etc., write North American Glass 1998, The Guilford Handcraft Center, P.O.Box 589, Guilford CT 06437 11/16/97

GLASS PAINTING In article <>, wrote: >good day!!!
>Does it cost too much money to do glass painting??? We would like to know
>if it's easy to learn this kind of craft. Is there any particular book
>that you should recommend????????

The expenses required for glass painting are: a kiln capable of reaching 1250F. A used pottery or metal enameling kiln will work, however a top element kiln designed for glass is preferable. I built my kilns for much less than manufactured kilns cost. you will need a kiln shelf and some kiln wash. Next you need glass enamels or glass stainers colors. These usually come in powdered form so you need to mix them with a medium and binder. This can be as simple as water and gum arabic, or as elaborate as using European acrylic water based medium (which I personally prefer). To mix the paint you need a large palette knife (cake knife) or a Braun hand blender. To apply the paint you need paint brushes. Almost any brush will work. I like bristle brushes, however sign painters brushes will give you the longest stroke. To do traditional glass painting you need a badger blender. These are very expensive, but they give the painter the ability to shade smooth and blend the paint. I have most often encountered glass paints on drinking glasses. To manufacture "Ronald Mcdonald" glasses the glass enamels are silkscreened on to decal paper. The decals are applied to the glass and it is fired to 1050F. You can silk screen on to flat glass easily.

The book I recommend is "The Art Of Painting On Glass" by Albinus Elskus. This book is available through most stained glass suppliers. Before the late 19th century all stained glass windows were painted and fired on every piece of glass. Opalescent glass allowed artists to paint on fewer pieces. A major effect of paint on transparent hand blown glass is that the paint on the surface stops your eye at the surface, so you are not looking through the window, but at the surface. Do a local church tour and look at the glass painting. I'm sure you will be impressed at the skill and artistry the old timers had.

If you are interested go for it. I personally find glass painting liberates me from having to use lead to hold a project together. and allows me to work on thicker (harder to break) glass.

Bert Weiss, Bert Weiss Glass Studio, Painted Art Glass, Custom Productions, Architectural and Sculptural Cast Glass, Collaborative Art Glass, Lighting design

Subject: Re: Chihuly From: "Jeff Mentuck" Date: Fri, 5 Dec 1997 09:14:39 -0500 > Anybody got any good "glass jokes" out there?
What's the difference between a glassblower and a Mutual fund???
Eventually a mutual fund matures and makes money!

CASTING A SMALL GLORY HOLE - Over the last week or so I have been working on a small glory hole that is to serve other purposes. Yesterday and today I was cooking it out and was impressed that I was able to do the whole cooking process to 1000F.

Besides making a small glory hole for furnace glass working, I am also going to use it for doing some forging of long thin steel items and as a foundry furnace for some moderately serious casting. Therefore, I built the thing as a tube, open at the bottom/back. When used as a glass glory hole and foundry furnace, the back/bottom will be covered with a cast disk. When used for forging, I will have to have an adjustable opening on the back.

I am casting the thing in a large can, about the size for caramel corn, 10" diameter, 14" tall. About two inches of National IRC 25 insulating castable were cast by taking a coil of sheet metal and turning it inward until the right size.

NOTE: To produce a cylinder of sheet metal exactly two inches smaller than another is easy. Use a piece of metal longer than will just go around. Place the sheet metal inside the larger and mark down the edge of the overlap. Take out the sheet metal and mark a line 6.28" (6 9/32") away. Make a cylinder, lining up the edge and the new line, and the result will be exactly 2" smaller than the beginning. Why? Because 6.28 is 2 times Pi (3.14159) which converts the diameter to a circumference. Making it 2" smaller leaves a 1" gap; 3" (9 7/16") smaller for a 1.5" gap; 4" (12 9/16") smaller for a 2" gap.

Two things I might have done and did not were: 1) Precast several pieces of castable 2" high to use as spacers between the inner cylinder and the wall, and 2) Position either a precast burner port or a core to make such a port in the gap. For consequences of the latter, see below.

National (and other firms) instructions call for a gradual heating pattern after the castable has set. This pattern is raise at 50F per hour to 300F, hold for 6 hours, raise at 50F/hour to 600F, hold 6 hours, raise at 50F/hour to 1000F and hold for 6 hours. I use the controller I use on my annealler, which uses plugin connectors.

The heating element is 1000 watts mounted on a castable block. Some time ago, I poured a castable block about an inch thick and 10" long. Using plasticine clay, I made a path for the element and supported two brass bolts to be cast into the block. After the block had set, I removed the clay carefully and cured the block in the annealer. Short lengths of heavy copper wire were covered with high temp insulation and then ceramic wire nuts were used to attach an ordinary appliance chord. I use the block for drying out and preheating my furnace and glory hole which sit out in the weather when not being used. (Blocks actually, I made two. The element costs about $10 at my hardware store.)

Back to the glory hole I am casting. Before I cured the unit, removed the inner shell and drilled a burner port.

NEAT EFFECT - Today at the store a young customer dropped a marble down the 30" deep white plastic tubes we use to display our 3' brass tubing. They were talking about using chewing gum or sticky tape to pull it out, but I decided to match one of the tubes to the size of the marble and suck it out. As I lowered the brass tube down into the plastic tube, I was struck by the spectacular effect of the light from the ceiling lights as it reflected down the tube and was scattered by the glass.

Have you considered what might happen to your glass if you placed small white lights in opaque tubes that release the light at the surface of or in the middle of your glass? If you are making small shapes, marbles or beads, the brass tubing I was using is sold at most hobby shops and many hardware stores. We happen to stock it in larger sizes than many stores do (up to 5/8") but the effect of releasing light at the surface should work with tubes of other kinds and with inner reflections from paint or aluminum foil. Most hardware stores will have aluminum tubing up to 1" in diameter. 12/10/97

* I will precede my postings of Hot Glass Bits like items with HB in case some people want to skip them. Some will be as general as this one, some specifically for furnace working.

Pilchuck Glass School '98 [, Pilchuck Glass School, 315 Second Avenue So., Suite 200, Seattle WA 98104-2618, 206-621-8422, FAX:, 206-621-0713] is one of the premier places to learn about glass as an artist. They do offer beginning classes, but the cost is so high ($2400 for two weeks, room, board, tuition & fees) that I would expect most people would want to take their first classes elsewhere. On the other hand, the quality is so high that more experienced artists have told me that they learn in new and interesting ways and can expect to sell the glass they blow for more than the cost of going. Attendance is immersion in glass. This year more beginning classes are offered than I have seen before. Depending on the kind of class, admission is juried or done by lottery from the applications on hand on March 2.

'98 has five two week sessions, beginning May 26, June 16, July 7, July 28, and August 18. Because my strong interest is furnace work, I will list that first, then other activities. Applications are due March 2, some classes are juried. Visit the web site and call or write for a catalog if interested.

FURNACE WORK - Beg.Glass Blowing, Mark Gibeau & Lori Hedemark; Glass Blowing, Painting & Tai Chi, Erwin & Valentin Eisch; Venetian Glass Blowing, Lino Tagliapietra, Checco Ongaro, Josiah McElheny; Advanced Blowing and Design Concepts, Dante Marioni, Benjamin Moore; Beg.Glass Blowing, Shunhi Omura; Advanced Solid and Blowing Techniques, Petr Novotny; Solid Worked Glass, Dino Rosin; Advanced Glass Blowing, Jan-Erik Ritzman; Intro.Glass Blowing, Paul Cunningham.

LAMPWORKING - Flame Working Soda-Lime Glass, Carl Ittig;
OTHER HOT GLASS - Glass Casting Survey, Mitchell Gaudet; Kilncast Sculpture, Patrick Martin; Hot and Kilncast Sculpture, Tina Aufiero; Kilncast Sculpture, Irene Frolic; Hot Glass Casting, Paul Cunningham; Neon and Hot Glass, Cork Marcheschi;
COLD GLASS - Coldworking and Engraving, Mario Seguso; Fundamentals of Hot and Cold Glass, Jane Bruce; Traditional and Contemporary Mosaic, Felice Nittolo; Laminated Glass Sculpture, Maria Legossy; Painted Glass: A Collage Approach, Gerhard Ribka.

IN ADDITION to the people named above, two artists-in-residence will be on hand for each session who are given the opportunity to work in glass without previous experience and Visiting Artists who participate in the program with presentations and demonstrations. Posted 12/22/97

Recent issues of two periodicals related mostly to hot are on my desk.

Glass magazine [UrbanGlass, 647 Fulton St., Brooklyn NY 11217-1112, 1-718-625- 3685,, $28/yr, $52/2yr, qtrly, 5 issues to new subscribers] is the only pure glass Art magazine. It is put out, with subsidiary funding, but a non-profit studio/school operation in New York City. It absolutely does not talk about technique or show pictures of how glass is worked. Much of the information about the current practice of art glass is to be drawn from the very high quality color ads from galleries that fill the magazine.

Number 69, the Winter 97 issue has a special section on Lampworking featuring a discussion of the work of Shane Fero and Paul Stankard along with a portfolio of artists. Other feature articles explore Louise Bourgeois sculpture and the work of Fritz Dreisbach, who has stood at the heart of the studio hot glass movement since it began. The Stankard article in particular makes shreds of "glass isn't art" arguments that Glass publishes rather too often for my taste.

The Independent Glassblower [% David Gruenig, RFD #2 Box 238-B, Lyndonville VT 05851, $25/yr $25 each year for back issues] is back after suspending publication for about six months while David moved. IGB is a quarterly newsletter of technical information about furnace glass working. David is continuing the issue numbers and "dates", expecting to catch up by more frequent publication. This one is #46, Jun/Jul/Aug 97. David does not cover technique.

This issue includes a recipe and notes about a red glass batch with suggestions for changing compatibility. A series of letters about iridizing, eye protection, and doors and roofs along with several full page notes and ads finishes the issue.

Subject: Re: BTU/temp for various torch gases From: (MarthaE) Date: 7 Jan 1998 19:19:00 GMT

I found a web site that listed the following data. I don't remember the site's web address, but it was a site for the company selling the Pro 2000 Fuel Gas (which I've never heard of before). I'm not sure how accurate this info is, since I found a different web site (this one about MAPP gas) that states its "gas flame produces 2,405 BTUs/cf with a 5301-degree-F flame." Anyway, here it is.

Gas Values
Total heating value (vaporized), BTUs/lb: 21,500
Heat value of gas, BTUs/cu.ft.: 1,480
Flame temp. in oxygen, Fahrenheit: 5,589
Primary flame, BTUs/cu.ft.: 350
Secondary flame: 1,130
 MAPP Gas:
Total heating value (vaporized), BTUs/lb: 21,100
Heat value of gas, BTUs/cu.ft.: 2,380
Flame temp. in oxygen, Fahrenheit: 5,301
Primary flame, BTUs/cu.ft.: 484
Secondary flame: 1,896
Total heating value (vaporized), BTUs/lb: 21,800
Heat value of gas, BTUs/cu.ft.: 2,371
Flame temp. in oxygen, Fahrenheit: 5,295
Primary flame, BTUs/cu.ft.: 433
Secondary flame: 1,938
Total heating value (vaporized), BTUs/lb: 21,640
Heat value of gas, BTUs/cu.ft.: 2,563
Flame temp. in oxygen, Fahrenheit: 4,579
Primary flame, BTUs/cu.ft.: 295
Secondary flame: 2,268
Pro 2000 Fuel Gas:
Total heating value (vaporized), BTUs/lb: 22,040
Heat value of gas, BTUs/cu.ft.: 2,612
Flame temp. in oxygen, Fahrenheit: 5,400
Primary flame, BTUs/cu.ft.: 468
Secondary flame: 2,144 (Mark Charles) writes:
>I've been pricing ramp-type controllers & the lowest priced one I've found is
>a 50 amp Olympic sold by Laguna Clay for $383. I'm a penny pincher so I want
>to check around. Are there any lower priced ones out there with comparable
>quality? Thanks in advance to those who reply.

This is the least expensive way I know is the following (from Omega 1-800-TC- OMEGA, Page numbers are in Temperature Handbook.
CN76020 ramping controller dc Pulse/ac SSR, $189 page P-96
DH-1-8-K-12 12 inch type K thermocouple, 8 gauge, $19, page A-13
GMP-K-MF pair of miniconnectors, K type, $5.50, page G-8
PR-K-24 24 gauge type K wire - 25' $14.38, 50' $23, page H-19
SSR481D50 50 amp solid state relay, DC control, $53, page P143
FHS-6 Low temp rise heat sink, $21, page P-143
Also needed, 50 amp wiring, plugs and/or outlets and case.
Total cost, $301.88

What this will give you is a very small unit with PID learning and memory (retains all settings when power is cut off) that will do a single ramp up or down over a time up to 99 hours with a power off or temp hold at the end. This is a 4 button controller with temp and setpoint display.

It also gives a unit with a nuisance method of setting temps that resulted in my spending $39 extra for -4SP, a four setpoint feature that holds four different temperatures selected by two switches. The problem with the temp setting is that as you hold the up (or down arrow) the setting changes first by 1's, then by 10's, then by 100's. I found it incredibly easy to overshoot the setting I wanted, so now I just leave one set at the annealing point and another set at the strain point, etc.

HORIZONS [The New England Craft Program, 108-P N. Main Street, Sunderland MA 01375, 413-665-0300, FAX: 412-665-4141] announces its 1998 programs. These range from egg painting to internet web design to cyanotypes. Some programs are overseas. All of the hot glass programs take place in western Massachusetts. Most classes are 3 days. Housing is available, but not required.

April 28-27, Glass Casting/Hot Glass with Neal Dobbins $295+*
May 9-11, Glassblowing, Beginning & Intermediate with Peter Houk, $315+*
June 13-15, Kiln-Formed Glass with Newy Fagan, $245+*. Marbles, Marbles, Marbles, Adventures in Lampworking Glass with Sally Prasch, $245+*
August 13-16, Lampworking, Idea Building/Shaping Glass in the Flame, Bandhu Scott Dunham, $310+*
August 13-18, Glassblowing with Kelmis Fernandez, $520+*
August 12-22, Add-on Glassblowing, further time to work, $385+*
October 10-12, Glassblowing, Focussing In, with Jim Holmes, $320+*. Glass Beadmaking, Lampworking 2, Sally Prasch, $255+*

*Lab fee is $90-125 for hot glass depending on length of course and materials used, charged at end of course. 1/12/98

Glass Magazine [647 Fulton St., Brooklyn NY 11217, 718-625-3685, $28/yr qrtrly - 5 issues for new subscribers, back issues $7] comes from UrbanGlass and the Spring 98 issue features stories on artists from outside the glass community including Rauschenburg, Baltimore Glassman, Kiki Smith and four featured in Glass Outside of Glass. Dorothy Hafner gets a serious photo and word essay.

One point made is that glass has replaced bronze as a medium where it is acceptable for the artist to work with a team, unlike - say - clay, where a number of attempts were made to bring the attention of non-clay artists to the medium and it didn't work.

Glass mag is almost entirely hot glass - blown and cast with a dash of lampwork.

One reason for subscribing is the glorious color photography of the gallery ads, featuring in this issue Dan Dailey, Jose Chardiet, , Kait Rhoads, Mark Peiser, William Morris, Dale Chihuly, Giles Bettison and Lino Tagliapietra in the first ten pages. 3/23/98

UrbanGlass [647 Fulton St., Brooklyn NY 11217, 718-625-3685 x 0, register at x237, fax:718-625-3685, e-mail:] announces summer intensives - weeklong classes Monday thru Friday 9am - 3pm.
Beginning Glassblowing, 6/22-6/26 $550, Kait Rhoads - vessel forms, teamwork and communication.
Solid Sculpting, 6/1-6/5, $550, Peet Sasaki, both solid mass and detailed bit work will be covered. (beginning glassblowing required)
Sculptural Hot Casting, 6/22-6/26, $600, Gene Koss, this advanced teacher will cover casting into sand, wood, metal and "machines" (basic casting required)
How to build a Furnace, 7/13-7/17, $400 Charlie Correll, building a 400# tank furnace
Slumping and Fusing, 6/1-6/5, $550, Dorothy Hafner, explore color composition with Bullseye glass and this well known artist
Lampworking, 7/6-7/10, $500, Sally Prasch, soft and hard glass, various tools and intermediate techniques. (basic skills required)
Lampworking, 5/29-5/31 (weekend), $400, Paul Stankard
Stained Glass, Mosaic, Advanced Neon Art, Sculptural Glass Construction, Two more involving painting and mixed media 3/23/98

Watlow has a site with a technical information page. If you need the info, here is what you find.

Equations: Delta/Wye Equations, Power Estimating Equations, Ohm's Law, Temperature Conversion Formulas Guides: Corrosion Guide, Agency Standards for Temperature and Power Controllers, Power Controller Comparisons, Power Controller Quick Reference, Temperature Sensor Comparison Guide

Reference Data: Amperage Conversions, Conversion Formulas, Heat Loss Factors and Graphs, Properties Non-Metallic Solids, Properties Metals, Properties of Metals in Liquid State, Properties Liquids, Properties Air and Gases, Estimated Wattage Requirements, Thermocouple Types & EMF vs. Temperature, Recommended Upper Temperature Limites For Thermoelements, Thermoelement Properties, Thermocouple Wire Specifications & Tolerances, Thermocouple Standards and Color Codes, RTD Tolerances, Classes and Comparisons

Supplier Selection Criteria, Systematic approach to supplier evaluation.

Tutorials: Glossary, Maximizing Heater Performance, General Method for Determining Heater Requirements, Evaluating Sensor Placement In A Thermal System

c Watlow Electric Manufacturing Company 1997


Webmaster @

I am a customer of Omega and frequently refer people to 1-800- TC-OMEGA to get the Temperature Handbook in connection with my avocation - furnace glassblowing.

Just before I came to this site, for the first time, I visited the Watlow site. Unlike this (Omega) site, which delays access to data by requiring download of half a dozen or so GIF images, the Watlow site slams the text in place and then adds images. In my case, I went through three pages, picking choices from the text, in about the time I had to sit watching the main page open on Omega. Irritating. Hope the site is worth looking through.

-------------------------- Hi, I need to ask a question that most here may laugh at, but I really want to know, and how else do I learn but by asking? when forming glass, can old glass be used and melted? How hot does the glass need to be? How are things like drinking glasses made commercially? where are molds gotten for glass making? Thanks lots for any help.

Bill Hi Bill,

Welcome to this section of the HandCrafts Forum!

Fundamentally, glass is one of the most recyclable materials around. Remelting glass requires somewhat less total energy than originally melting it up from the batch, so it's not only possible, but in many areas, considered quite responsible to remelt and recycle glass, especially glass used for containers.

Now, there are all kinds of glass, and uses for same, and different types of glass work better for various commercial or production sorts of processes. Also, especially for the container industries, the glass must be free of hazardous impurities, so at least in the area of bottles and jars, the glass is segregated out, from other types of glass. Most of the "art" glass that we use for stained glass (for example) contains all sorts of pigments, and heavy metal contaminants that account for the colors and opacity. Thus, these glasses are not suitable for use in food grade vessels, because of the potential leeching of these hazardous materials.

As far as temperature, glass of different compositions will melt at different temperatures. Glass is rather like taffy, even when glowing red hot, it never really pours like water. By definition, glass is an amorphous solid, without a specific melting point.

In the real world, most glass begins to bend and soften in the 1000 degree (F) range, and it can be heated on up into the range of 2500 degrees (F) or higher, depending on any number of factors. Depending on the formulation of the glass, past a certain temperature, it will begin to deteriorate into other things, and it's not glass any more.

Most commercial bottles, are blown into steel (or other metal) molds. A measured lump of molten glass is placed over the mold, and a blast of hot air moves it into the mold, coating the inside of the mold with the glass. The mold is allowed to cool somewhat, and then is opened up to release the still hot glass vessel, where it is allowed to cool in a controlled manner, so as to anneal the glass, making it suitable for use at room temperature. Production lines use large numbers of such molds, all configured to keep the process moving right along, and I've seen a few such facilities, it's amazing to watch. If you ever cut a machine made bottle apart, you'll find that the glass is not necessarily uniform in thickness in the bottle, but that overall it's thick enough to hold together.

Now, "art glass" vessels are another thing entirely. They can be blown on a metal pipe, each formed one at a time by the glass artist, and with all sorts of shapes, colors, and textures as part of the design. Vessels can also be cast in various techniques using kilns, again with all sorts of variations and methods.

I hope this helps a bit, it's a very general overview sort of message, but at least it's a start. If you have specific questions, I would think that some of our members here might be able to come up with some better answers.

Peace -Gerry

GLASS FOCUS [9323 N.Olcott Ave. Morton Grove IL 60053-1752, 847-967-8433 FAX 847-967-8440, $30, $18 student, 6/year] is a newsletter now in its 12th year that exists primarily for art glass collectors while still providing a lot of timely information on galleries, museums and other events that can be of use to artists. For example, in the current APR/MAY 98 issue includes detailed notes on SOFA (contemporary decorative arts), The Glass Skin exhibit at Corning (sculptural glass with emphasis on surface effects), the G.A.S. Conference in Japan, and a Waterford Glass Workshop. Over sixty galleries have events listed (no pictures). 4/13/98

PUBLIC GLASS - a not for profit center for glass art in the Bay area of San Francisco. Public Glass 1750 Armstrong Avenue San Francisco, California 94124TEL (415) 671- 4916 FAX (415) 671-4917 California's only public access glass facility Offering Classes, Workshops, Demonstrations, and Rentals in: Glass Blowing, Kiln Casting, Cold Working, Sand Casting, Slumping/Fusing


Establish the Bay Area's only public access glass facility The mission of Public Glass is to act as a magnet, attracting people from the local arts community to gather, learn and share their knowledge and unique experiences. It will enrich the San Francisco Bay Area by providing a well- equipped, professionally managed glass working facility for the Public.

Enhance the recognition of glass as an art form


Offer workshops, classes, lectures, and demonstrations Public Glass is dedicated to the establishment of a glass facility where a creative environment for the artists and the public will expand their knowledge and appreciation of glass art. It embraces a vast and diverse glass community by providing a center that will be an integral part of a greater arts community that includes the Benicia glass studios, Oakland Museum, Yerba Buena Center for the Arts, Hunter's Point Naval Shipyard studios, California College of Arts and Crafts and San Jose State University.

Offer rental facilities for practicing artists


Make it accessible to the public and all artists from the beginning student to the professional

It functions primarily as a rental facility providing an ongoing work place for artists to pursue their creative endeavors. The center also presents an opportunity to develop a cooperative relationship with the public by providing special programs designed to expose and educate people in the art of glass. These programs include classes, workshops, lectures and demonstrations. This facility will enrich the art community by expanding the concept of glass as a sculptural medium and providing artists with an opportunity to explore the vast characteristics of glass and its potential.

Staff the facility and organization with professionals Public Glass will strive from the beginning to be the best. The studio is well built, properly maintained and professionally managed. The staff consists of experienced artists who are proficient technicians and teachers.

Equipment and facilities for glassblowing, hot ladle casting, kiln casting, fusing, coldworking and related techniques

Accessibility is key to the success of Public Glass. Classes and workshops, tailored for the beginner to advanced students, will be available as soon as possible. A technician will be on staff at all times to ensure the proper use of the facilities. Collaborative alliances with CCAC, the Academy of Art College, SFAI and local high schools are already being established, as well as with other glass organizations.

For information call (415)671-4916 or e-mail to:

Subj: Re: fire buckets Date: 98-04-14 11:48:23 EDT From: (Donald R. McKinney) Reply-to: To: (MikeFirth) File: paperweight.jpg (65216 bytes) DL Time (TCP/IP): <1 minute MikeFirth wrote:

> << If you want to know more, feel free to e-mail me.>>

> As a furnace worker, I would like to more about techniques and methods

> on this very small scale, working with cold or warm glass.

Hi Mike,

The Murphy Fire Bucket is a small glory hole, very lightweight and portable. The front opening is only 4" and a max. working depth of about 4". It is very energy efficient, getting about 20 hrs. on one 5 gal. propane cylinder. I make paperweights and marbles up to about 3.5" in diameter. I also use it for making stringer and cane. Yes, the size is limiting but, it is all I have worked with for the past five years and even though I am in the process of building a larger glory hole, I will continue to teach with the Murphy and use it to make marbles and paperweights. I teach on the road and need a unit that is easily transportable and this works. I am currently using a Jen-Ken electric crucible furnace as my melting furnace. It works fine for the small projects that I do and teach. I am using Bullseye 1501 cullet which fines out better than any glass I have ever used. I am also using Bullseye sheet glass, cut into pieces and strips, and preheated on a piece of 1/4" stainless steel sitting on top of a propane fired Coleman camp stove. It's a pretty slick little setup and my students love it. For about a three thousand dollar investment someone can be doing hot glass at home. I even blow Christmas ornaments up to about 3.5" in diameter so it is possible to blow small items as well.

Don McKinney, The Glass Palette Studio and Gallery

Bee County College will once again have 5 day classes this summer. Application deadline is April 30. Fees are $150. Find your own housing.

Beginning Glassblowing, May 18-22, and June 8-12 (previously announced May 25- 29 canceled due to conflict with G.A.S. Conference.)

Glass Fusing & Slumping, June 1-5.

Classes taught by Jayne Duryea, Chairperson, Visual Arts Division, 512-354- 2322.

Bee County College, 3800 Charco Road, Beeville TX 78102

Beeville is about 1/3 of the way from Corpus Christi to San Antonio, just off I-37. 4/16/98

I rather recently got an announcement of this class, which starts so soon it is probably full, but if you are interested, it can't hurt to call.

May 1-14, Karen Willenbrink, nationally known solid glass sculpture artist will be offering a class that can be taken for credit or not at Jacksonville University [2800 Univeristy Boulevard North, Jacksonville FL 32211-3394, 904- 745-7394 FAX 904-745-7375]

This is for students with some glassblowing experience. Bit work, color application, and manipulation of blown forms are included with use of the garage to hold for assembly complex glass components.

Tuition and fees total $1805 for undergrad credit (3 hrs) and $1241 for grad credit (3 hrs) or non-credit.

The studio, which began in 1972, is housed in a new facility completed in 1996. The studio has a 220 glass furnace, 5 glory holes, (3 - 12"dia x 24", 1 - 18" dia. x 28" and 1 - 8" dia x 10") and 5 annealers (2 - 36 x 54 x 10" deep, 3 - 38 x 28 x 12" deep.) The program is directed by Caroline Madden, JU assistant professor of art. 4/16/98

HANDS-ON GLASS [261 Baker Street, Corning NY 14830 607-962-3044] has sent their 1998 Summer Programs Weeklong Classes schedule (postmark April 15) No specific deadline is given for applying. Classes run 9am-4pm Monday- Friday

July 6-10 Beginning Glassblowing Rodi Rovner $350

July 6-10 Engraving Plus Harold Gross $300

July 13-17 Flameworking Techniques Al Janelle $350

July 20-24 Beginning Glassblowing Rodi Rovner $350

July 27-31 Glassblowing: Beyond the Basics Rodi Rovner & Steve Bertron $375

Aug 3-7 Sandcasting Mark Kobasz $410

Aug 10-14 Murrine Techniques Peter Secrest & Cretchen Lapp Hamlin $385

July 11 & 25 Saturday only workshops in Beadmaking and Small Sculpture $95


From: (MikeFirth) Date: 15 Apr 1998 04:35:01 GMT

This book by Edward T. Schmid is a dangerous book. I got my copy yesterday and read about 30 pages of the 320 pages of material and the blowing time for the things I want to do has passed the 1,000 hour mark.

While this book does not replace Ed's Big Handbook of Glassblowing as an introduction to techniques and attitudes of getting involved in glass, it is not as fearsome as the title might reflect. If I were teaching classes and felt I had a sure set of exercises and skills to bring students up from beginner, I would encourage purchase of this book because the essentials of working glass at the advanced beginner and low intermediate level are there at the beginning of the book.

Ed's books are hand written and hand drawn with a number of drawings per page that might make it an economic disaster if the drawings were processed separately. The beginning of this book is a series of drawings of glass objects with explicit statements of the techniques needed for making them, which reference sections of the book.

Ed gives alternative methods of doing many things (such as punties) and makes his attitude of "If it works, do it." clear and specific.

This is a book to drive moderately experienced glassblowers crazy. I can't judge its effect on the well worn, but it seems to go well beyond what I expect to do for a couple of years. I am wandering around Texas next week visiting various glass studios and talking to some strong glass blowers and will see what they think.

Edward T. Schmid Glass Mountain Press, 927 Yew Street, Bellingham, WA 98226, $32.95 + $4 for priority mail, 320 pages, ISBN 0-9638728-1-8

LINO VIDEO - The Corning Museum of Glass [Sales Department, One Museum Way, Corning NY 14830-2253, Orders: 607-937-5371 x246, FAX 607-937-3352, e-mail] is offering a 30 minute video tape Cane Working with Lino Tagliapietra for $29.95 ( VHS, $35.95 PAL) +$2.50 s&h US, $3.75 foreign. The tape includes "striking closeups of [his] techniques and a detailed look at a variety of his works." 5/17/98

SCOOPS & BALLS - Some places that sell steel have premade domes designed to be welded on the ends of pipe, either to seal them or to top them when they are posts. One place is Central Steel & Supply [9550 S. Central Expy, Dallas TX 75239, 972-225-6131] I bought several sizes and welded a smaller pair into a ball shape and then to a 1/2" square steel tube to use as a gathering ball and a single larger one to another tube to use as a scoop. While the smaller ones make a good approximation of a sphere while larger ones are flatter and would end up looking more like a hamburger bun. More details later as to usefulness.

STUDIO AT CORNING - Although probably too late to get into a class, it can't hurt to ask if an opening exists. The people involved in teaching these classes are some of the best in the country at their skills, I am being a bit lazy in not mentioning most of them. Complete text of mailing is on their site. Tuition is $485 for 1 week, $850 for two. [Amy Schwartz, The Studio, of The Corning Museum of Glass, One Museum Way, Corning NY 14830-2253, (607) 974-6467, FAX: (607) 974-6370,]

6/8/98 - 6/19/98 -Session 1-Two torch & one kiln class

6/22/98 - 6/27/98 -Session 2-One torch, furnace, & carving

6/29/98 - 7/4/98 -Session 3-Beg.furn.,torch, carving

7/6/98 - 7/11/98 -Session 4-Venetian, Lamp Sculpture, Kiln Cast.

7/13/98 - 7/18/98 -Session 5-Furn.Sculpture, Troch, Cold sculpture

7/20/98 - 7/30/98 -Session 6-Furn.Surface, Torch tech.,Pate de Verre

8/10/98 - 8/10/98 -Session 7-Venetian, Beadmaking

8/24/98 - 8/29/98 -Session methods, Torch.Explor, Pate

8/31/98 - 9/5/98 -Session 9-Furn.Casting, Moretti, Mosaics

9/9/98 - W 9/17/98 -Session 10-Furn.Teamwork,Torch Bandhu,Surface

Subj: Hello from Livermore Date: 98-06-01 14:10:50 EDT From: (Roger...)

Hi Mike,

No, we have not floated away from all the El Nino rain. It just seems that way. Its been a while since my last message, so I should bring you up to date. A month ago I retired from my day-job and have started doing glass in earnest -- well, at least more than a few hours a week. I have changed my shop around to accomodate a small, electric furnace -- one of the Jen-Ken crucible furnaces. A couple of weeks ago I fired the furnace for the first time. The experience was mixed.

First, the furnace itself works fine. I would recommend it to anyone wanting to work with small amounts of glass. I have yet to receive my electric bill, but I have calculated it should cost about $10-$15 per day to run. It would be a good addition to a full hot shop that wants to work with several colors at once -- e.g. making millefiori, or dipping core vessels, etc.

My main problem was with the glass composition itself. I purchased cullet from Frantz Bead that was supposed to be Moretti compatible. It is indeed compatible in COE, but has a VERY short working time. This problem was compounded by the fact that I have not yet built a glory hole for reheat. I was using my Major bench burner for working the glass on the punty. I am working on a glory this week.

This glass melted and fined about as you would expect, but it was totally unworkable at 1850 degrees. I ended up raising the temp to 1950. (These temps are as indicated on the pyrometer that is part of the Jen-Ken. I do not have a secondary sensor to confirm these temps.) At least I could gather glass and work it for short periods. The best I was able to do was a couple of paperweights in which the final form was accomplished through "air-marvering" to shape. I suspect this glass was formulated for casting and not for blowing.

If you have any suggestions of how to extend the working time, I would appreciate it. I am considering adding some Lithium Carbonate to the crucibles on the next run. It is supposed to extend the working time of glass (and reduce the viscosity). Or if you have a recipe for 103 COE/Moretti compatible glass you would be willing to share, I have been talking to East Bay Batch about putting together a small run.

Perhaps I need to consider changing to 90 COE glass. It does seem like most furnace workers (and paperweight makers) use Schott, Bullseye, Spruce Pine, East Bay, etc. The problem is the cost and availability of color bars. There is a lot more to work with in Moretti color. ----

I have signed up for two weeks of classes at Cal Poly in San Luis Obisbo, CA. Ed Schmid and Elena Enos will be part of the instruction staff. I am looking forward to working with them again. I want to see if I can concentrate with Ed on doing Ventian-style blowing -- classic shapes from cane pickups. This is something I think I can do in my shop and want to get good at it. Actually, I want to focus on just a few techniques so I can get better at it -- at least good enough to sell some pieces to support my habit. ----

How are things with you? I see you on the news group from time to time. Still miss getting "Hot Glass Bits" every few months. There is just something about a printed news letter that makes it "better".

Hope you and your wife are in good health and not getting banged around by life too much. And hopefully the weather this spring has been good enough for you to fire up the furnace once in a while. To paraphrase Robert Duvall in "Apocalypse Now", "Gawd I love the smell of burning PROPANE in the morning!!"

Take care, Roger... Roger Peterson (Soon to be DBA as) "California Glassmith, LLC" Livermore, CA

In a message dated 98-06-01 14:10:50 EDT, you write: << I have signed up for two weeks of classes at Cal Poly in San Luis Obisbo, CA. Ed Schmid .. ...>>

Sigh. As I said on the news group, his advanced glassblowing book is dangerous, I have page after page marked with things I would like to try.

I finished casting the dome on the new furnace yesterday. Now have to dry and bake it out. I cast a small glory hole/forge/casting furnace in a can several weeks ago and fired it up full this past weekend (on a day when the temp broke a 100, a ha!) It has a small (1" IPS) burner driven by a blower and low pressure propane and it just kept getting hotter and hotter. I was measuring temps for a while and go up into the 2000F+ without half trying. I actually burned copper out of the brass I was trying to melt, probably ruined it. Temp yesterday (5/31) hit 102.8 on the shaded front porch with the sun on the otherside of the house; perfect weather for getting glassblowing equipment into operation, finally.

The cheapest way to measure temps accurately is the converters available from AW Sperry (cheaper) and Fluke (more available, Grainger has them, listed under Test Instruments, Accessories, not Temp measurement) They cost $55-75 and take a K type thermo couple. Save money by allowing use of any digital voltmeter, including cheap Radio Shack as I use, which can be used for other purposes.

A glory hole will give you much better heating than a torch - it radiates heat on all sides, for one thing.

I am not strong on glass chemistry. Drew Ebelhare uses Gabbert Cullet and wishes he hadn't started with it, but now has hundreds of yards of millefiori drawn in it and has to keep compatibility. The amount of color available in color bar seems astounding to me, but then I haven't done more than glance at the Moretti display at G.A.S. and haven't tried to compare or count. I don't expect to use a lot of color in my work.

I find the temp you are working the glass to be rather low, but then it may be that glass. I have found that Spruce Pine cullet (batch melted by others and given to me from their crackoff buckets) has a good working point about 2050- 2100.

All the best on your new venture and new equipment. Tell me about the class and what happens with you. MF 6/1/98

CASTING THE DOME - I finally got everything together to cast the dome on my furnace, after the lower part has been sitting around for some time. My method was to use the glass pot, in place, to support a disk of foam core board that filled the hole. I then laid paper to fill the slight gap and separate the top from the bottom. I then used old foam packing blocks cut to shape to give me the basic shape. (I think a wad of newspaper with some spray glue on it, then covered with paper mache strips might work as well.) I used foam insulation from a can to give the smooth dome inside shape. This was an experiment and I felt more comfortable with the carved block I used on my glory hole. I actually had problems with cans of the foam I brought home not working, which delayed me. I brought some low expansion foam, which worked ok, but was costly for what I wanted to do and fairly tough to carve when set. The high expansion (triple expansion) worked better and sets harder. I used an old thin piece of sheeting to inject the foam under and then pull on (wearing gloves) to make the smooth dome as the foam expanded. To make the access port, I pinned up a collar of pasteboard and put foam inside.

Once the foam had set, I used AP Green 25 Plus Insulating Castable. I mixed 50 pounds (one bag) at a time in my plastic wheelbarrow and then moved it with a shovel and a trowel. I mixed it fairly stiff and worked it with my hands to make the shape I wanted, working carefully to maintain thickness, since a tendency to get thin on the the least accessable side has been apparent in the past. Since the mixing was not totally even, I used some of the less stiff mix to moisten areas that seems to need it. The dome took two bags with a small amount of waste to wash from the barrow. I then wrapped the dome in plastic and periodically sprayed water on it over the next 24 hours. I will let it dry some and cut and burn out the foam (smelly, icky, environmentally not correct) inside before heating gradually to the various temps mentioned in the directions.

ENDING THIS ISSUE - I have been carrying this material as Hot Glass Bits Notes 98A on my computer, and suddenly today it seems fitting to end the issue with this note from Roger Peterson, the final achievement of casting the dome for my furnace over the weekend, starting my first day of being Manager of the Electrical Department at Elliott's Hardware and first day (maybe) of riding my bike three days a week to work as recommended by my doctor, who just put me on minimal beta blocker to bring down my marginally high blood pressure before more problems occur (and I felt better as soon as I started taking it.)

The decision I have made is to post the issue to my web page and mail a post card to people who have been getting issues in the past saying they can have a print issue for $5. Until I was in the middle of my reply to Roger, I had not been able to settle on something to do. 6/1/98


Hot Glass Bits is a personal chronological record of my wanderings through glassblowing and the bits and pieces of knowledge I gather along the way. It includes things I try, thoughts I have, information I receive, and reports on things I do. In many ways it is an edited diary and events calendar about glassblowing. If it is useful to others, it is worth the effort.

WHOAMI? - Mike Firth is a 54 year old, low experience glassblower who signed up for his first class in '91 without having seen anyone blow, although he had seen TV shows, and had done stained glass and worked clear tubing in the past. He has built cheap equipment in his back yard to learn and practice and is now on his second round, more traditional, of equipment. When not blowing, he is a married employee of the best hardware store around.

The legal stuff: Working glass is inherently dangerous, involving heavy materials that can be razor sharp, so hot that damage can be done before feeling occurs, with chemicals immediately poisonous, dusts that can damage the lungs, and heat sources that can wreck the eyes. Understand the safe practices required and use them to blow beautiful glass.

Blow Good Glass Hot Glass in Texas

Dallas - Kittrell-Riffkind Art Glass, [5100 Beltline Suite, Suite 820, 214- 239-7957]

Dallas: Carlyn Galerie, [6137 Luther Lane, 214-368-2828] A Gallerie of Glass into November

In Wimberley, southwest of Austin, Sable V Fine Art Gallery, [The Courtyard Overlooking Cypress Creek, 512-847-8975]

The MSC Forsyth Center Galleries [Student Center, Texas A&M University, College Station, 409-845-9251]

Hot Glass Bits, Mike Firth 1

Contact Mike Firth

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