What are slump molds made of ?

What are slump molds made of ?

     While this his is a loaded question because there are many things that can be used, the most common mold materials used to slump glass are ceramic and stainless steel.

      When it comes to ceramic molds, the most common ceramic is bisque fired white bodied earthenware ceramic. This type ceramic is fired to cone 06 (about 1850F), so it does not shrink or change much at slumping temperatures (between 1200F and 1300F).  This type of ceramic is also fairly porous, so it accepts water-based kiln washes very well.  In fact, almost any clay that is bisque fired to cone 06 or just hotter is suitable for making slump molds.  It becomes harder to kiln wash ceramics that have been fired much hotter than cone 06 (stoneware ceramics and porcelains, for example).  If using boron nitride as your kiln wash, you may even be able to use glazed dishes or bowls as slump molds.

     When it comes to stainless steel molds, these are usually simpler shapes than the ceramic molds. Drape molds, simple curves, and bowls, are frequently seen in stainless steel. It is difficult to apply water-based kiln wash to stainless steel molds, so most fusers use boron nitride spray instead. If you have metalworking skills and are making your own mold with stainless steel, type 303, 304, and 316 are common, and a slightly roughened finish may hold the boron nitride a little better than a smooth surface.

     Other metals than stainless steel can be used so long as they survive the 1300F high range of slumping. Cold rolled steel can be used but will scale will form and flake off over time when heated making it important to sand and re-apply kiln wash periodically. Stainless steel mesh is great for making molds that are one of a kind. Brass and copper will likely survive, but we don’t recommend galvanized steel since it can produce unhealthy gasses when heated.

      Other materials that can be used to make slump molds include fiber board, fiber paper, and Silkemat (a non-woven ceramic blanket type material).  Occasionally, chalk, plaster/silica mixes, refractory insulation, refractory cements, and fire bricks are used.

     If you need a mold to shape your fused glass art, check out the selection of ceramic and stainless steel molds available at www.SWArtGlass.com.

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