How to prevent this from warping when glaze firing?

[Fusionous]

7 hours ago, Jeff Longtin said:

To expand on  Kswans point: my guess is that you took three round tubes and set them on a table and draped the clay slab over them? I would suggest you make three clay tubes the same diamter as the tubes you started with and fire the slab on them. Where the slab touches the clay tubes will need to remain unglazed, and the tubes would need to be kiln washed but this would give you the support you're missing.

I would close off the ends of the clay tubes to prevent them from collapsing as well.

1 side glazed and 1 side unglazed?

[Chilly]

As previous comments, clay that is born flat wants to return there, as these two pictures show:

 

 

I know that doesn't help for this project, but changing the method of forming the clay in future might help.  I made the next version as a thrown dish, and cut the shape, leaving the up-pointing tail from the thrown rim.  It didn't droop.

Edited December 18, 2022 by Chilly
Typo

[Fusionous]

On 12/10/2022 at 12:52 AM, Callie Beller Diesel said:

Is there room in your situation to allow for negotiation for more time on this deadline? If you’re dealing with a client, this could be your best option for delivering the quality of work you want to present. Clay is notoriously temperamental, and explaining that you think your client deserves the best possible work you can offer and that you’ll settle for nothing less for them may be a possibility. If this isn’t a culturally acceptable practice, feel free to disregard.

If what I’m reading is correct: you have more versions of this sculpture that have not been glaze fired yet, and you want to be able to prevent similar warping in the next ones. If that assumption is the correct one, I’d put a pin setter of some kind underneath the sculpture at the points where you know it will sag so that it’s supported. The small pinpoints that are left from the setter can be buffed out easily. If you don’t have a suitable pin setter, you can make one out of wads of clay and lengths of Kanthal wire (the same as your kiln elements). 

If I don’t have my assumptions correct and you need to try and repair this exact piece and you cannot obtain more time, the solution is maybe a bit more risky. You have to not only push the end pieces down, but the middle dips in the piece also have to be raised from the surface. In addition to what Pres recommended about weighing down the end pieces with setters in a re-fire, you also need to build supports to re-elevate the middle parts. This may result in the piece sitting the way you want it to, but the piece may have more irregularities in it.

 

On 12/10/2022 at 1:02 AM, Min said:

+1

Fill the gap under the middle 2 downward dips then the ends won't be pulled up.

Thank you Min, Callie for your suggestion! I'm cautiously optimistic as the 2nd try worked! Here's the picture. Fired with pin setters beneath the 2 dips plus the sides!