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Striking Art Studio LLC ________________

Specializing in Glass Art, Encaustics & Jewelry
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Kiln Casting > Pate de Verre > Flameworking > Beadmaking > Fusing > Clay > Painting > Prints > Encaustics & Collage >  

VARIOUS TYPES OF KILN CASTING

Scroll down to view & read about various types of kiln casting, and to see why this

type of glass can be so expensive! 

 

 

Hollow Core Vessels

 

Ancestral Journeys
©Jamie McKay 2005
Gaffers Lead Crystal
 
Mysteries & Memories
©Jamie McKay 2005
Gaffers Lead Crystal
 
 
Life Came Pouring Out
©Jamie McKay 2004
Gaffers Lead Crystal
 
Ancient Waters
©Jamie McKay 2003
Gaffers Lead Crystal
 
Dreaming the World into Being
©Jamie McKay 2003
Gaffers Lead Crystal
 
 

  Solid Sculpture

 

 

  The Great Void

  ©Jamie McKay 2002

  Gaffers Lead Crystal

 

 

Open Face Casting ~ Bas Relief Tiles

The luminous finish on these tiles is created by firing glass frit in an open face mold made of plaster & silica.  The side of the tile in contact with the mold's surface obtains a soft matt finish, while the side exposed to the high heat of the kiln obtains a fire polished surface.  (More info below describing various kiln casting processes.)

 

Neo-Lav Lady

©Jamie McKay 2007

Bullseye Soda-Lime Glass

 

 

 

  World Tree

  ©Jamie McKay 2007

  Recycled Bottle Glass

  (yes that is a blasted crack in the tile!)

 

Test Tiles

©Jamie McKay 2007

Recycled Bottle Glass

 

 

  By the Light of the Moon

  ©Jamie McKay 2001

  Gaffers Lead Crystal

 

 

 

Variations on Kiln Casting

(click on pate de verre above to see & read about this specialty form of kiln casting)

 
Quick Overview:  There are as many ways to create a model as there are ways and recipes to create a refractory mold, both of which you need when making a piece of glass art using the various kiln casting techniques shown above.  Casting models are typically made from clay or wax and then invested with fireable mold material (refratory molds).  The model is removed (directly or by a lost wax casting technique), the empty mold cleaned, filled with glass and fired in a kiln OR fired in such a way that a specific amount of glass will melt into the mold's empty spaces during the firing.  Everything is brought down to room temp after having been fired according to a precise schedule that controls the heating, annealing, and cooling phases. When the mold and glass inside are cool enough, the mold is then devested so that the glass piece that was buried inside can be removed and later coldworked to reveal a gorgeous piece of luminous glass art ~ assuming everything went according to plan! (see the tree tile above for an example of things NOT going according to plan!)
 
More Detail:  Bas relief tiles tend to be made from clay; the tile is then invested in a mold called an open face casting by pouring a slurry of plaster silica into some type of mold containment system (such as a coddle box, tin pan, heavy roof felt form, etc).  If the model material would not be easy to remove from the mold's interior (such as with a hollow core vessel or with a solid sculpture containing major undercuts that would trap the model inside the mold), the model is usually made of wax with sprue channels and vents added to the final wax form to help ensure that all areas inside the mold will be filled with glass during the firing process without trapping air bubbles.  The sprued wax model is then invested in mold material by either pouring into the containment form OR by handbuilding the mold to build up a shell of multiple layers around the model. 
 
There are many different recipes for making refractory molds (molds that have to endure high firing temps), but they usually revolve around equal portions of plaster and silica ammended with other refractory or strengthening materials such as sand, vermiculite, grogs, fiberglass shorts, ceramic shell materials, etc).  Face coats are sometimes brushed or splashed onto the model before the actual mold material is applied or poured, and these pre-coats can include talc or kaolin (epk) in a plaster silica base, to help the mold material come away from the glass surface more easily after the firing is completed. 
 
Once the mold is created and cured, the model is removed either directly (as in clay being pulled out of a tile mold) or by steaming/melting the wax out of a hollow core mold via a process called Cierre Perdue or Lost Wax casting.  Once the mold is emptied of the original modeling  material, it is rinsed and proofed for flaws (which are fixed as needed) before it is loaded & leveled on a sand covered shelf in the kiln.  The appropriate amount of glass (frit, cullet, billet, or sheet) can either be piled directly into the mold (as with an open face casting for a tile) OR suspended in a prepped crucible (w/ a hole in the bottom) over the top of the mold so that the glass will melt & pour into the mold during the high temp phase of the firing. 
 
The digital controller on the kiln is programmed with a very carefully controlled firing schedule that takes into account the dampness of the mold, the type of glass being used, and the thickness & complexity of the glass and mold material (along with the number of molds being loaded into the kiln), so that the proper heating, annealing and cooling phases will take place without cracking the mold or its entombed glass form.  Once the firing is completed and everything is fully back to room temp, the mold material is carefully devested to free the buried glass form inside.  The glass piece then goes through a sometimes tedious process of coldworking to remove any plaster core materials, surface irregularities or flashing, and any glass overfills left in the sprue cup and sprue channels. And of course at the appropriate times during this entire process, you have been wearing a particulate rated respirator (N95 or better) and working in an environment that can be properly cleaned of any silica residues to protect your lungs!
 
For a more complicated hollow vessel form, this whole process of modeling, investing, firing, devesting & coldworking usually takes about 3 to 4 weeks, which is why kiln cast glass tends to be so expensive!  The next time you see a piece of beautiful kiln cast glass by an unknown glass artist, just realize that they are likely not recooping much of the time invested in the piece, so have mercy when you see the price and just think, wow what a deal!
 
jamie j mckay