Warpage

[Columbine]

I fired a large hand built bowl and when it came out it was warped in the sense that I put it in circular and it came out somewhat elliptical. Is there a way to avoid this? Should I have let it dry longer before firing it?

[MatthewV]

Clay has a memory. If you had to squish and squash it to be round it may recall its elliptical upbringing. Evenly drying (in my experience fast or slow makes no difference) is also a factor.

 

The other solution is in the design. Notice how many bowls have a flare at the lip? This helps them stay round. In general, finishing a handbuilt piece with a good rim is proper workwomanship. A good foot and a finished lip is lesson one in my class.

[Columbine]

Hmm, that's a good point. I made it with a seam on one side, maybe that is the cause. Maybe next time I'll make two seems halfway between. 

[GiselleNo5]

The word "warpage" caught my eye only I read it like "warPAGE" and I wondered for a full minute if it was a page or blog about war and how that had to do with ceramics, or possibly similar to rampaging before my brain caught up and I felt quite silly. 

 

What I do a lot with my items is let them dry slowly in a plastic bin with a slightly cracked lid for a long time. 

 

Also, some clay bodies are better for use with hand building or slab building. What kind of clay were you using? I have a groggy red clay and a sandy tan clay that are fabulous. They never crack or warp. I have another smooth lovely clay that ripples and warps if I use it to make tissue boxes. So annoying. 

[Joseph Fireborn]

Can you post a picture of the bowl. It would help us see what happened to it better. If your clay gets very soft at the final temps there is a good chance it will warp if you don't have "structure" built into your bowl. This "structure" can be as simple as a rolled rim, a lip, putting indents or bends in the pot. Another method is to make the foot bigger so that the wall isn't slumping but has a solid foundation. You could also change clays. When I was firing some porcelains they didn't like my small footed bowls and they slumped. However if I fire that same shape in stoneware it stayed exactly the same.

 

So it "depends" as many here would say. A picture and clay body type would help us help you better.

[Chris Campbell]

The seam itself will pull the bowl out of shape if it is too thick ... Meaning thicker than the rest of the bowl.

Sometimes the way you close the seam will influence this ... Side to side pressure might be a factor. Close the seam with up and down motions and see if that helps.

[oldlady]

another thing that can cause warping is the placement in a kiln load.  if i make a large bowl, i try to center it on a shelf and surround it with items of a smaller but similar size.  if you put a big bowl with one side a few inches from the elements and the other side near the center of the shelf, well.......................... guess what.

[Roberta12]

Ditto to everything said above.  And I should add that I had a lot of warp-age (I saw WarPage as well, Giselle!)  with Bmix.  A lot.  I have not had that problem with other stonewares or porcelains.  Just bmix. 

 

Roberta

[flowerdry]

That's at least 3 for "War Page!!!"