Help my slabs are cracking up

[eoteceramics]

Hi again,

Ive the kiln loaded, but due to all the good advice here I need to reschedule the firing schedule.

 I think it was heating too rapidly causing explosions and cracks.

So I have a Nabatherm B130 controller with 4 ramps and a possible two temp points

Can anyone suggest a firing schedule, Bisque or should I candle and cool  then bisque.?

I cant do both in one firing given the number of ramps/ heat..... I think

Thanks for your time Julia

[WoodlandPotter]

Hi Julia,

Sorry, no. I have no experience using silica sand, I am afraid. I simply bisque fire my tiles flat on the shelves and stilt them in the glaze firing. I haven't had any problems.  I would have looked for a solution had I seen cracks, or splits, or whatever, but no... all have come out fine. Maybe I've been lucky. I don't know. I have made some large, but to be fair most have been small tiles, 5 inches by 5 inches, or 5 inches by 7 inches. Maybe that's the reason I haven't run into any problems with them.

Hmm.... I wonder if the following makes a difference:

When making tiles, I use the technique I learned when I was a kid from a potter who railed that the only correct way to create slabs was to throw them. It involves throwing a  flattened ball of well kneaded clay down on a  piece of cardboard at an angle. The bottom part of the clay will grab on the surface, while the top part of the clay will stretch in the direction of the throw. It's reminiscent of the way a pizzeria cook stretches pizza dough, only in the case of clay, it is stretched by throwing it down, lifting it off, turning it and throwing it down again, repeatedly until the slab is the desired thickness.  I have been practicing this since I was ten, so it's easier for me to make slabs this way, than any other way. Maybe the tiles I cut from these slabs are more resistant to cracking because having been stretched, most of the clay particles lay in the same direction. I don't know. It's an idea.