Plate glass sink Question

Tyler Frisby · Post by **Tyler Frisby** » Sun Feb 22, 2004 9:13 pm

I've been fusing sinks out of plate glass recently but have had a problem develop where they crack on the first or second slump. I'm cutting a 19 circle out of 1/4 inch glass and tack fusing broken peices of glass from the same piece at 1410, them slumping at 1350. I've had a rash of cracking problems lately... any suggestions ? I have had succes in the past and am using the same kiln.

Also im slumping in 2 stages (single shallow slump first)

Tom White · Post by **Tom White** » Sun Feb 22, 2004 10:48 pm

The most likely cause for cracking in a second firing is poor anealing in the first firing or too rapid heating in the second firing. Please post your firing schedule for both the tack fuse firing and the slump firing. Be sure to include anealing information for both firings.

Best wishes,
Tom in Texas

charlie · Post by **charlie** » Mon Feb 23, 2004 12:35 pm

also, i think float fuses at a hier temp than b.e. i tmay not be fully fused.

in that case 1410 is too low, and 1350 is too high for slumping too.

Bert Weiss · Post by **Bert Weiss** » Mon Feb 23, 2004 12:53 pm

I see a few problems. First of all it soumnds like you are not annealing or you are reheating too fast. Second of all 1/4" with some blips fused on is not thick enough for a sink in my estimation. I make sinks 3/4" thick. I have seen commercial sinks as thin as 3/8". I have a job now recreating one that broke before it's buyer got it home from Italy. I'm doing it in 3/4".

BTW 2 layers of 3/8" (10mm) works better than 3 layers of 1/4". Fusing float for a sink requires an hour soak around 1220 to squeeze out the bubbles. I fuse float at 1420 with a 40 minute soak. Slumping usually works fine at between 1280 and 1310 depending on the shape and size.