The percentage they shrink is relatively different between Art Clay and PMC. Art Clay shrinks about 8 to 9% after firing whereas PMC shrinks about 10 to 15%. PMC's earlier formulation shrinks even more. 30%!
So, that was like the utmost primary consideration that you have to take into account in many aspects of a design.
Detailed designs however may benefit from this shrinkage because the shrinkage makes the details even more apparent.
I think the shrinkage issue poses the biggest problem for ring making. It's quite difficult to determine the size. Take this ring that I made for example.... I intended it to fit my middle finger but even after taking into account the shrinkage, the ring still ended up too small for my middle finger. It ended up fitting my ring finger but it's even worse when I got back Malaysia. I don't know if it's an issue with the weight or the heat that my fingers are a bit 'bloated' that now it can't even fit into my ring finger lor! So, yea..... I can't fit into this ring no more. :(
It's just a simple band with a red heart shape cubic zirconia. If you're wondering why it's a bit black, that's because I had it oxidised. I didn't like the look of that ring in bright silver. So, I had it 'blacken'. :P
I know the finishing's a bit rough as well. I think you probably need to do a lot of sanding and such at the bone dry stage to 'polish up' the work before firing, otherwise it turns up to be a very rudimentary piece of work.
I did this ring in a rush cuz I was running out of time already. It was near the end of the session already and we need to rush it off to fire them in the kiln in order for it to be ready for me to bring home.
Well, it was my fault for spending too much time on the other ring (which did not survive the kiln! :( I'll talk about that next time) But the shank for the other ring appears more polished than this one cuz I manage to spend some time on sanding and 'polishing up' the work a bit.
Well, not to say it's not feasible to make a ring or come up with polished pieces of work using metal clay. But I do believe it requires more trial and error as well as handling experiences to find your way around it.
One interesting point is you can do stone setting without any knowlege of silversmithing. You pretty much just plonk the stone in. Well, not exactly 'just' because there are also some factors to take into consideration, failure of which, risking the piece not surviving the firing process.
The only gemstones which can be used to be fired with the clay is lab grown gemstones like cubic zirconia. Even then, certain colours seems to change above certain temperature.
Unfortunately, natural stones like precious gemstones and pearls cannot be fired at all. Not to mean that they can't be used with metal clay. They would require stone setting knowledge from traditional silversmithing to set these stones on.
Very interesting nevertheless, ain't it? ;)