Threading, Stringer, and Cane

Rev. ... 2003-03-16, -11-22

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Drawing with glass

Other Techniques With Glass

The process of putting lines of color onto a hot piece is called threading and may be done with molten color in a process of the same name or by having long thin pieces of color called stringer when small and cane when larger. This page explores the process of threading a piece and of making stringer and cane, particularly since I made a machine to help a solo worker do both.

Composite picture of threading process.Threading is commonly done with a rig of two pairs of bearings mounted on small angle supports in a way that allows them to be pivoted.  In the picture, part of the threading unit is shown at left, with a similar bearing out of the picture down left.  The bolt just below the pipe allows pivoting the bracket with the two wheels on it.  Each time the pipe is turned counter clockwise, it moves away by a small amount as most clearly shown on the center inset. [pictures taken at Texas Hot Glass, Chris Marrs working, 2003-11-22] A steady yoke is right in front of the bucket.



Threading and rod pulling rig of Mike Firth The bearings may come from bicycle wheels, wheelbarrow replacement bearings, commercial bearings, or (as in my case) replacement wheels for sliding glass doors. This last choice offers two sizes of wheels with a reasonably sharp edge and a ball bearing inside with a 1/4" bore for mounting. I mounted mine on small sections of 1/8" x 1.5" aluminum angle. The brackets are mounted, usually on a portable base, about 18-24" apart, with a single bolt so they can be pivoted. The roller rig is available commercially, most often with a 1/4" flat aluminum plate for a base. In the picture, the pipe is shown (bad detail) sitting on the wheels (the rest of the rig is for pulling thread alone.)

In use, the brackets are placed perpendicular to the line between them when just rotating the glass is desired. If both sets of bearings are pivoted to the same angle, when the pipe or punty is rolled on them, it will travel lengthwise a uniform amount with each turn, so if hot glass is touched to the piece, it will form a thread that spirals down the piece.

THREADING - Most commonly, a lump of glass color is preheated in the color kiln, then picked up on a hot punty and further heated and marvered to form a molten limp cone. The tip is brought to the piece and touched and the body pulled back as the piece is spun. Controlling the rate of spin determines how quickly the glass is pulled off and thus how thin the thread is. As the glass cools, the rate must change. Upon completion, the thread must normally be broken or cut free. The piece is then reheated to fuse the thread into the glass.

If the piece is placed in an optic before threading, forming ridges on the piece, when it is threaded and reheated, the threads over the valleys will normally melt and draw back to where the glass touches the peaks, thus forming spots of color around the piece.

STRINGER - is long thin pieces of glass, all one color. It can be purchased or pulled from color bar (or from color melted by the artist.) At least one artist, Toots Zynski, uses it as an artistic medium using a rig with a bicycle wheel to pull dozens of yards at a time of very thin stringer; which are then woven and arranged and slumped to vessel shapes. Stringer is most often 1/16" to 1/8" in diameter. It is placed in optics to arrange the color around the bottoms of grooves in the piece. It is aligned on a grooved marver to permit rolling the hot glass piece for pickup. It may be laid on a marver in scatter fashion along with frit and powder to make an abstract design for pickup. Stringer is also used in constructing latticino where white and opaque colored stringer is picked up evenly spaced around clear and then the reheated glass is marvered and twisted to form a rod with spiral color, which is then used in pieces.

CANE - In the most limited definition, cane is just thick stringer, but almost always it is more than that, being a composite of colors that form a design. Slices of cane with designs may be cut to form millefiori slices or murrini designs. If part of the pattern is clear glass, then the side view of the cane may show multiple straight lines or spiral lines to be incorporated in a design. Pattern cane is made by aligning short pieces of solid color cane, cased solid color cane, or by making specially shaped cane cores. One pattern cane may become a part of another pattern.

DRAWING with glass - Using this term just here may be a bit confusing, because drawing can also mean pulling out metal into rods or wire, but the topic is drawing as with a pencil. If a glass piece is partially formed and then either taken to rollers or hung, for a short time it can be worked before it must be reheated to avoid shattering. Using stringer and a torch, it is possible to melt the end of the stringer while maneuvering the glass and draw pictures or otherwise write on the glass. The work I have seen reminds me of the line drawings of Picasso, either pencil or when he drew in the air with a flashlight for David Duncan. Because a person is working on a surface at about 1400F, which has an odd/unflat shape, with an instrument that must be heated and adjusted constantly, a simple drawing is the expected result.

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