© 2009 Anthony Foo.
This is a great question and it also demonstrates the advantages of paperclay.
I like to build rather large, tall pieces, but don't have the patience for regular clay to firm up before continuing. As a result, my earlier pieces did slump. Any large moist piece of clay will slump. However with paperclay, there are techniques you can employ to shorten the wait time for the piece to firm up.
One of the advantages of paperclay is that it will tolerate "forced drying" ie either drying your piece in direct sun, which is actually the mildest treatment compared to the other methods I will discuss here. These are experiences gathered from my own work.
I've used a heat gun at the highest setting to help dry my piece faster. It's actually used to strip paint by heating up the paint so it bubbles up and can be scrapped off.
A propane/butane torch works well too. It's the kind that you use for heating up copper pipes for plumbing works.
Use caution and always wear protective goggles and leather gloves when using these instruments. DISCLAIMER: Use at your own risk.
The intense heat WILL NOT crack nor cause your piece to explode. You will see steam coming out of from the area where you are directing the heat. You will also see specks of clay/pulp burning and popping off. This is natural as there is organic pulp in the clay and that will burn off. You will actually see you piece drying before your eyes. Depending on how thick your work is, it may take some time for it to firm up. I find it's best to keep the heat source moving to distribute the heat evenly across the area you want to firm up. If your piece is really thick, the outside may feel firm and dry, but deep inside it may still be moist. It will take some time for the moisture that deep within your piece to dry out.
If you are energy conscious, then just use our abundant So. Calif sun to dry out your piece while you relax, clean up, have a cup of coffee or just work on another section of your project.
If you have a smaller piece you need dry quickly, you can use the above mentioned techniques or employ the services of a microwave. It's best to use an old one that you can dedicate to your art and not mix it with food preparation in your kitchen. No, the piece will not explode in the microwave. I started with a low setting for about a 15 second burst at a time. Eventually I got bolder and was able to zap it at the highest setting for a minute or so. Again, steam will escape from your piece so handle with care when taking it out. This method is a great way to get your cup. vase, mug handles to firm up quickly for attachment to the rest of the piece.
Why are the above methods possible with paperclay and not so with regular clay?
The answer lies in the paper pulp fibers which act like conduits (and in reality, they actually are) to allow the water/steam to safely escape to the outside. The forced drying in one area of your work will draw the water from other areas (thru the pulp fibers), balance out the water content and prevent, minimize cracking.
And what happens if my piece cracks? I'll cover this in another post.
Hope this helps.