Help with firing programme

[Simoncooley.sculptor 0]

Hello everyone, I’m a working sculptor with 40 year’s experience using clay but am entirely new to firing.

Could anyone advise me about the best programme for firing in an electric kiln for this sculpture?

The construction is made from  1” (25mm) square solid pieces and the clay is Scarva Earthstone ES20 smooth textured and is stoneware.  Fires bisque 1000 degrees c  and stoneware at 1280 degrees c.

My concern is that because of the open nature of the construction, it may warp and crack if the speed is wrong.  It is approx 40cm long and 15cm wide.  It should be completely dry by now, but may have picked up some atmospheric dampness (although it has been in a cupboard for 8 months).

Also, is it safe to put other objects made from different clays (but within the same firing temp parameters) in the same firing?

I would be utterly grateful for any help.

 

Thank you in anticipation.

 

Simon

[Min 3,458]

 

I think the  firing schedule Beth Cavener uses could be adapted to your sculpture. I would skip the drying ramps but start with an overnight candling of the kiln, 10C up to 80C and hold overnight. For the firing change her top temperature of 1148C to 1000C (if you want to go to bisque temperature). I would also add a ramp 4 in the firing schedule to slow down the firing towards the top.  Rate 3 would go at 90C to 700C, 0 hold. Rate 4 would go at 42C to 1000C. This slower rate of climb allows for more impurities to burn out from clays containing them. I would do the cool down rates the same as the Cavener schedule.

Yes, it's fine to fire different claybodies together in the same load. 

The other thing I would do when firing your sculpture is to make a thin slab to fit underneath the sculpture from the same clay it's made from. Dry it between boards so it stays flat then put it underneath the sculpture so when the sculpture shrinks during firing it will shrink with the waster slab and not get hung up on the kiln shelf. When you go to glaze fire the piece use the same waster slab underneath it again.

Welcome to the forum!

[Simoncooley.sculptor 0]

Many thanks.  That’s so helpful!  What thickness should I make the waster slab?

Simon

[Fred Sweet 172]

1/4 inch or  .6 cm. Whichever you’re most comfortable with. You can put a layer of kiln wash on between the bisque and glaze firing if you choose to glaze your piece.

[Simoncooley.sculptor 0]

Thanks a lot Fred..Should the batt wash dry before the 2nd firing and what stops the ¼ inch panel warping? Apologies for taking time with such novice questions!

[neilestrick 4,624]

The waster slab may warp or crack, but that's okay. Put some alumina wax or kiln wash on the slab to keep your sculpture from sticking to it.

[Simoncooley.sculptor 0]

Neil, thank you!  Just to be clear,  how precise a thickness does the slab need to be throughout its length and width, I’m rolling it now but despite using guide rails I am getting some slight dips here and there. Thanks again ..Simon

[Min 3,458]

Thats fine, just get it as flat as you can. I make mine very thin, like 2 -3 mm. Are you going to glaze the piece or ?

[Simoncooley.sculptor 0]

Thanks Min, I’ve made several at 6mm since I have some other things to fire as well so fingers crossed!  To be honest I don’t have a clue about glazing but  raw clay appeals, perhaps with something that seals it ?  So grateful for all the advice from you people.