Rims Warping When Throwing With Soft Clay

[OBP]

hello, I am throwing with a clay that has a lot of molochite, because I raku.

I am actually using Commercial clays ST material mixed 50:50 with a grogged stoneware.

I have found it easier to throw if I use it quite soft, the clay actually moves better and I am happy with the shape  and the rims which are spot on when I cut the pots off the wheel. However they keep warping on drying.

Am I stretching the clay too thin? This does seem easier to do when the clay is wetter.

I have tried drying vases on their rims, but they still warp out of shape.

Should I be using harder clay?

Any suggestions to resolve this problem would be greatly appreciated, it's driving me mad.

Thankyou.

[Foxden]

I suspect uneven drying. Have you ever tried to just leave a bowl slowly turning on the wheel while it naturally dried? The rotation exposes the bowl evenly to the atmosphere and as a result one side doesn't dry faster than another. If that solves it, maybe tent your work to slow down the drying and keep it even.

[MatthewV]

A picture would tell a bigger story.

 

There are many subtle features in the bowls I throw. The rim is compacted with leather. There is usually a slight outward flare. The clay has been pushed outward from the pulled inverted-cone. The shape and working process have a huge influence on warpage. I dry bowls upside-down after they have set.

 

These aspects are more prone to warping problems:  thin rimmed, simple curve, thrown with soft clay, and uneven drying.

[alabama]

Check the room for drafts using a lit candle. The flame shouldn't flicker.

 

With winter still in place, the drafts are caused by vents or cold air cascading down the walls.

 

See ya,

Alabama

[Bob Coyle]

A quick fix might be to slow drying. Cover the clay with plastic shopping bags with a couple of one inch slices made in them with a knife. Tuck the bags around the bottom so that all the drying takes place through the small cuts. It will take longer but If you still get warping, it probably is not from uneven drying. Then you can look at whether you are producing strains with your throwing technique.

[glazenerd]

Bill Powell from Queensland, Australia throws massive platters in both stoneware and porcelain. He has a rather unique way of overcoming weight and clay properties. If you are looking for something more specific, I can email him ask him if he has a video more in line with what you need.

 

Nerd

>>Look at the shelves behind his wheel when he is throwing.. he fires a rather mean crystalline glaze as well.

[oldlady]

EXCELLENT!  thank you for that beautiful example of a master at work.  i even liked most of the music. yes, the background has a marvelous collection of great pots.  what a joy to watch clay respond that way to the lightest touch.  

[Roberta12]

Wow!!! For people who don't work in clay, it might have been like watching paint dry, but I was completely fascinated to the end!  And he does love his propane torch!!!  Great Video nerd!!  Thanks for sharing.

 

Roberta

[oldlady]

roberta, that was a somewhat normal torch.  our guild had a workshop where the artist pulled a burner out of the kiln to dry the pot he was working on.  F L A M E S!!