firing figurative sculptural pieces

[Jacquie Jacobs]

I have been making a series of busts with a mid-red cone 6 clay and have no experience with firing...

I know some areas of the sculpture and much thicker than others and have punched some holes in the piece to vent it (also eyes are vents)

1. I was wondering if after 3 weeks of air drying if I should consider slowly extra drying the pieces in my oven at 200F to help mitigate any uneven shrinkage problems .

2. Also If I oven dry,  and do it a month before the firing,  will it still be useful or will the piece reabsorb humidity from the air? 

thank-you so much for any advice from experience!

I tried to upload a picture from My website with no luck ... so I will put the web address here...  ( they are pictured  in the greenware stage ) 

http://www.jacquiejacobs.org/new-blog/2023/8/3/ceramic-busts

[Min]

Hi Jacquie and welcome to the forum.

Are you going to have control over the firing of the busts? Have a look at the drying and firing schedule Beth Cavener Stichter uses as a very safe firing drying and firing schedule. (note she goes to cone 2 though and drying the clay out is included in the schedule) What you are aiming for is the evenness of the drying to prevent stressing the clay and getting cracks.

I know Toronto can be really humid in the summer, whether it's humid enough for the busts to reabsorb moisture from the air enough to make a difference in the firing I don't know. To be safe you could candle them overnight. (hold the kiln at a low temperature for 12 hours or so)

Beautiful work!

[Rae Reich]

Definitely want those beautiful figures to remain in one piece! Have they been hollowed out at all or are they mostly solid? You said you poked holes in them, are the vent holes going to a hollow core?

[PeterH]

A picture showing the inside of one of the busts might help. Even better if there is something like a ruler in shot to give the scale.

Either posted here or on your website.

[Callie Beller Diesel]

I would just add that if you elect to oven dry the piece, an oven has less sensitive controls than a computer controlled kiln. Note the increments that Cavener Stitcher uses. She takes 36+ hours to get to 225 F over 4 ramps. While that’s exaggerated, and definitely overkill for your purposes, the same principle applies. Oven drying could be too hot or heat up too fast for larger thermal mass items. If it’s going to dry more rapidly on the outside than the inside, that’s usually where the problems occur.

So +1 for the 12 hour preheat, but if your piece is thicker than standard beginner pottery, I’d opt for 175-180 F instead of 200. 

I’d take another note from that link and transport the pieces while they’re still leather hard, if you can. Bone dry work cracks much more easily.