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Firing Plaster Of Paris

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I am looking to support a biscuit fired lattice structure so i can machine it.  I will then need to remove the plaster any advice appreciated. If I enclose it in paster of paris and fire it will the plaster fall away from the fired ceramic if i submerge it in water?

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I would not fire the plaster!  Plaster likes to absorb water, and doesn't like to let it go.  It will explode in the kiln, due to that water.  

 

If I understand correctly, are you saying you built the clay lattice on the plaster, for support?

 

Generally, if you want a mold/ support that can be fired, artists will use cardboard/ paper that will burn away.  Or a ceramic mold, made out of the same clay body.  I use, and have my students use, clay props.  They shrink at the same rate as the clay item they are working on, and can be fired with the project if necessary.

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Do not use plaster of Paris.

There is a mixture used by sculptors that includes 1/3 silica flour. I can't remember the name..I thin it is called Ludo or something like that. it is used to cover wax models and burn out the wax. It is not the higher end colloidal silica process. You need to do more research on this.

I would use clay coils to support your lattice. I use them for many things in bisque firings.

Marcia

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The basic recipe for molds for kiln-casting glass is 1 part silica to 1 part pottery plaster, by weight.  Sometimes other additives are included for various purposes.  Here's a link to get you started http://www.bullseyeglass.com/images/stories/bullseye/PDF/TipSheets/tipsheet_08.pdf  See page 2 for the mold recipe.

 

This mold formulation crumbles away from a glass casting after firing in the range of 1500 - 1600 degrees F.  For your application, if the clay is already bisque fired there should not be an issue of it marring/adding texture to the surface.

 

Supporting a bisque structure for machining is an interesting concept and piques my curiosity.  Does the machining involve CNC?

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