2004-11-02 Rev. 2005-11-11, 2008-02-20, -02-24, 2009-02-16 (layout), -05-03, 2012-02-24
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Various products are called clay.
Earth clay is the traditional material dug from deposits in ground, wetted, formed, fired to brittle hardness at a high temperature. Once fired it will withstand high heat and if glazed hold water or food safely.
Plasticine or modeling clay is earth clay wetted with oil instead of water making a never drying sculpture material. With latex mold compound or silicone rubber, copies can be made in plaster, investment or wax, as here.
Precious metal clay (PMC) is silver, gold, bronze, or copper particles mixed with a binder that burns off in a kiln, leaving shrunken real metal jewelry. Cork clay is a material that can be worked with PMC and burns off leaving a hollow.
Modern polymer clay or polyclay is a solvent softened PVC plastic that can be baked hard in a household oven for colorful jewelry and figurines (my polymer page) and can be stuck to glass and baked - Polymer Clay on Found Objects Good overall discussion Eileen's Favorite Camp Craft - Polymer Clay on Glass Lessons
Paper clay is finely ground paper with glue that air hardens - a special form of paper mache.
Earth clay can be used with glass in various ways -
The glazes used on clay pottery are basically glass. Going
further with lumps of glass or glass incorporated into clay objects involves one
with the compatibility of the glass with the expansion and contraction of the
clay as well as the mass of the clay and its effect on the annealing cycle.
Depending on the effect desired, gluing the glass in place may be the best
choice. Crushed glass fused to clay surface:
Clay & Glass,
formed clay pendants with glass
Leila Cools Fused Glass
and Clay Pendants
Fusing Glass to Clay (reply)
"Glass sags then slumps then melts across the range of 1250F to 1550F. Cone 014 in pottery work is 1540 (subject to time to temp) so you should have no trouble melting the glass into place. I would strongly recommend making some dummy clay pieces, firing them, then placing marbles from the bag you expect to use and running the temp up, looking periodically to see how far they have melted, checking temp.
Glass requires controlled cooling to keep tension from cracking the glass. The mass of the clay has to be taken into consideration so you may have to take a couple of dozen hours bringing down the temp. You will need a ramping controller which you may not have. Depending on the shape of the holes and the relative Coefficients of Expansion of the clay and the glass, the glass may pop free of the clay and have to be glued back in place (E6000 works good for this.)"
It may be necessary to glaze the clay for the glass to behave in the desired way. Using a glaze, which should bind the thicker glass to the clay, will make compatibility a greater issue. Having a lump of glass in a hole in the clay may result in a rather small area of actually being glazed in place and may hold without cracking free during cooling.
|This is my first attempt at a clay form to blow glass into. As shown it has been bisque fired and painted with a transparent glaze that is colored pink to allow judgment of coverage. Before use it will be fired again. The form was slip cast in a plaster mold also used for casting wax shells. The lozenges were cut out and trimmed. The bottom was cut out to permit puntying the glass, since putting a bolt as used with the goblets is not practical. 2008-02-24|
Although I have been thinking of glass added
to pottery clay, several of the links found in a Google search involve silver
clay (PMC) to glass
Contact Mike Firth