My clay molded head is cracking as it dries. What can I do?

Keith Baudry

First, a few photos of it three days after molding. 

Then, a picture of it cracking for 3 days. Please explain to me what I’ve done wrong here and how to move forward?

I am thinking 20min a/b epoxy would fill the cracks and harden it, but I’m worried it will continue shrinking and somehow be worse. I wondered if there was something to be done with aluminum foil in the cracks?

I believe the issue stems totally from the oversized bust I used to build on. I went very large to reduce the amount of clay I’d need to build something so big, but maybe I should’ve used a different material. Any help is appreciated. Sooner the better!

Kai Rottmann

Hey Keith,

water based clays crack to 97% if they loose to much water.
The WED Clay EM 217 from Laguna is one of the only water based clays, which hold its shape very long and its cracking very late in the drying process.
Pottery- clays are done for drying complete without cracking.
The clay itself begins to shrink and if there is a hard core in the sculpture, which dant shrink as the clay does. the clay will crack. 

Did you use a hard core under your sculpt?

Chris Ellerby

Kai is correct.  Water based clay will pretty much always crack on you as it dries out.  As the moisture evaporates out of the clay it begins to shrink and crack.  If it shrinks around a hard core, it will crack.  If it shrinks faster in some areas than others, it will crack. 

If you want the sculpture to last a bit longer (if you are still working on it) you can place damp paper towels on the surface and cover it with a plastic garbage bag to keep the moisture in.  You then need to check on it every few days, adding new moist paper towels.  You are always working agains the clock, as you can't keep that process going forever.  I've known sculptors who have kept a water based clay sculpture (usually WED clay which is a bit more stable) alive for months, but you have to care for it like a living thing.

Water based clays are not intended to last forever.  Some can be fired in a kiln to create pottery, others would have the be molded so you can cast replicas of the original sculpt.  

Sometimes a dried water clay sculpt can be saved by lightly misting water onto it, then storing it with the damp paper towels and garbage bag mentioned above.  This gives the moisture time to return to the clay, and would need to be repeated slowly until the moisture can penetrate deep into the clay.  That process will take a few days, possibly over a week.  If you add moisture too quickly the outer layers will turn to soup and all you will have is a mess.  You don't need a lot of moisture, just a lot of time.

If you just want a sculpture to keep around, you can work in an oil based or polymer clay.

Sorry you've run into these problems.  It's never fun to lose a sculpture (though there is a possibility this one can be saved), at least you gained experience!  

Here is a video from by friend Gordon Tarpley that covers rehydrating a dried out WED clay sculpture.
https://www.youtube.com/watch?v=jlIy50M43tw

Hope that helps!

/Chris

Kai Rottmann

Hey Keith :-)
Is that a water based clay? You know, that the Water vaporates out of it, if you dont put a bag over it?

Maybe you could bring back the water and it starts to quill back to its older form. 

You need to spray lots of water over a long time over it.
Wetting the surface with water, put a wet towel over it and put a bag over it and make sure, that no air can come to it. 

After 6 hours, take a look what happened. At this stadium you may be able to fill the gaps with fresh clay.

If it helps, make sure that you mist your waterbased sculpture with water and bag it tight, so that no air can come to it the next time.
If you leave your sculpt alone for a longer time, do misting it with water all 5 days to keep it wet and make sure, that no air can come to it. 

I hope it helps.

Greets

Kai

Keith Baudry

Hi, thanks for responding. But I don’t think you answered the question. Are you saying there’s a material I should have used? Are you saying I should NEVER let the clay dry because that’s ridiculous. 

Yes, it is water based. I knew it would dry and evaporate, that’s what I wanted. I thought it would maintain its shape. Instead, it shrank and cracked. 

Keith Baudry

I absolutely did use a hard core. So 97% of the time the clay cracks ? How unfortunate ! I used a hard foam core that doesn’t compress. If I had used some other rig it might have had a different result? What about chicken wire?

It seems like plenty of people mold a mask from clay then let it dry before casting it with silicone or some other material. If the clay is always breaking, are they mold casting the clay before it’s dried, or just using it in a way that allows the clay to shrink over a compressable core as it dries ?

hmmm. You think I should add the water back to the clay and mold over a new core ? I was just going to fill the cracks with a quick hardening epoxy.