Ceramic Bisque for slumping

[Lenora]

I bought some replacement bisque at a ceramic Shop.   Are these OK to use for slumping glass

[Stephen Richard]

yes.  Kiln wash it an dry it before putting glass on it.  In general ceramic is best slumped into not draped over.

[Hartache]

yes.  Kiln wash it an dry it before putting glass on it.  In general ceramic is best slumped into not draped over.

And why is that? Because of the different COE's that glass and ceramic have!  Ceramic expands and contracts less with heat than glass does.  So if glass is slumped into a ceramic mold, when they cool, the glass will contract more and end up slightly smaller than the eramic mold - no problem.  If the glass is draped over a ceramic mold, when they cool, the glass will contract more than the mold and end up stuck on the mold or more probably broken.  There are shapes that will work, but in general, slump into a ceramic mold.

Rebecca

[artsbycole]

Rebeccas last post was right on. Generally slump into ceramics....Drape over steel.....
Roger

[Hartache]

Rebeccas last post was right on. Generally slump into ceramics....Drape over steel.....
Roger

And why is that?  (giggle)  Because of the different COE's that steel and ceramic have!  Steel expands and contracts more with heat than glass does.  So if glass is slumped into a steel mold, when they cool, the steel will contract more than glass and break the glass.  If the glass is draped over a steel mold, the mold will contract more than the glass - no problem.  There are shapes that will work, but in general, drape over a steel mold.

Rebecca

[Carmen]

Remember to drill a hole or 2 in the bisque mold before ever using it for fusing purposes. Also, when coating the mold put on at least 5 or 6 coats of kiln wash. Smooth any imperfections in the coated surface gently by running your hand over the mold. Always make sure Not to have any wash plugging up the holes. I usually poke a toothpick through the hole and move it around a bit. I can fire my mold several times before needing to re-apply more wash.

[Stephen Richard]

You should not need to renew the kiln wash unless:
it is mechanically damaged/scratched/etc
it is fired at too high a temperature, such as fire polish or tack fuse.  In these cases the kiln wash needs to be removed as it is likely to stick to the glass in the next firing.