This was an plaster casting experiment I made awhile back in early college, and the results were too cool!
I experimented with dental alginate to make plaster casts of appendages as part of a class. The results were fascinating; the alginate consistency was so fine that it adhered to every pore and wrinkle, contributing to an eerily life-like collection of disembodied hands and feet.
Dental alginate is a blue powder that's mixed with water and it takes a good while to set. Creating the molds felt like an eternity because in order to get a perfect mold of a hand, that hand can't even relax until the alginate begins to firm up after 10 to 15 minutes. To extract the hand from the mold, I had to be really careful with the alginate as it was so delicate -- it tore far too easily. This was kind of tough, as my subjects' hands needed to be lifted straight up and out of the mold. So I ripped a lot of molds.
Then I mixed the plaster, poured it into the molds, and hoped for the best. Most of them turned out really well, and the ones that didn't were even cooler. Some fingers had bubbles and were rather distorted, but were otherwise perfect with life-like creases and wrinkles.