Dr. Krantz: "Just poured... ahmm mixed the plaster and poured it in. Everybody seems to think you can't make plaster casts in snow but you sure can. Ahmm we made that one and it turned out fine. I made plaster casts of my first Irish Wolfhound's footprints in snow, and everyone said you can't do it and so I tried it; worked perfectly. When the plaster is starting to set, it warms up considerably but it is already set to a degree where it is not going to move."
Rick: "Well, I think that is one of the things they say is a problem (talking about the generated heat). But I think the main problem is water in the plaster freezing, and not curing the plaster itself. And so what happens, I have seen it, the print has a bunch of dry spots afterwards, it just gets riddled. But if you mix a 5% solution of Potassium sulfate with the plaster, it lowers the freezing temperature of the water in the plaster and allows it to set up. But that is in really cold environments."