I use water based clay and I have some problems with cracks. Any tips on how to avoid cracks? If the clay dries to fast it crack but I guess there are more tips .
Dont let the clay dry out . You might want to try hollowing out the clay before you let it dry. Cracks happen when the outside of the clay dries faster than the inside. You could all so try an oil based or something like sculpey.
"The only thing we have to do is die. Everything else is a choice."
Dry your clay slow.. try to keep parts you are not working on covered with plastic. The bigger your sculpture is the slower it needs to dry. Time and patience is key
The only thing you really can do is just keep it from drying too fast. I usually put the piece in a plastic bag with some damp paper towels and let it dry for a week.
Clay that already has small particles of hardened clay dust in it tends not too crack as much (perfect for firing too). If yours is standard smooth, the others pointed it perfectly that you need to let it dry super slow. Clay shrinks and will invariably crack if it doesn't dry at the same pace all around. Hollowing helps in that reguard.
To keep the clay moist when I work on it (weeks on end), I wrap it in damp cloth and add a spoonful of bleach in my spray bottle water (to avoid mildew and rot). I then seal the whole thing in a jumbo plastic bag.
To do a controled drying I gradualy remove thewater source. So the cloth get less and less water, then switching to paper towels since they dry faster, then nothing on top of the sculpt. I usually end it with a plastic bag on top (but opened at the bottom) with a small cup of water under and next to the piece. I all depends of the size / shape of your art and type of clay used.
It will split if it's too wet, as well. I have a bad habit of working too wet with clay and the results can be awful. Not too dry and not too wet - just find a balance.
Putting a plastic bag over it will help. It will still dry, but much slower than if it was out in the open.