Trying to create a rock face similar to what they demonstrate on the greatesthobby.com DVD (for those that have seen it). They use “casting plaster”. Is that the same as Hydrocal? Lightweight Hydrocal? If somebody could give me a brief explanation of plasters or other materials used to do this type of scenery work I would appreciate it. Thanks!
I use Hydrocal for mine. It is designed as a “casting plaster.” You mix it fairly thin for pouring into a mold, and it solidifies quickly. It takes paint very well once hard. After about 10 minutes in a mold, you can wrap the whole thing (plaster and mold together) around a curved surface, and then it will accept and hold the curvature when hard.
I use a different material called “Gypsolite” from Scenic Express for surfacing mountains, etc. It takes a lot longer to set up, so you can work it manually for a long time. I spread it with a small drywall or putty knife. It has a gritty uneven texture, which simulates earth very well. I mix some cheap brown paint in with the mix before I spread it so I don’t start with a white surface.
light weight hydrocal is wonderful and you pay dearly for that wonder. I have taken to using Plaster of Paris. It cures really fast and I can get more castings done in a session. I do not think you could use the wet plaster application with it.
I use premixed drywall seam cement as a top coat. That takes 24 hours to dry (not cure) and can be easily carved for 2 days. I mix it with paint and saw dust for my version of Goop.
You can buy sacks of a product called Gypsolite http://www.nationalgypsum.com/products/?query=cat:6&product=48 from Home Depot etc. There are other similar products. A sack will last forever and will only cost a few dollars. This material is perfect for convering foam and getting the basic scenery plaster done. Then use regular plaster of Paris for rock molds. These can be applied to wet Gypsolite and then you can use more of the Gypsolite to fill gaps between castings and generally smooth the castings into the scenery base. Structolite is another brand of this type of plaster.
I use regular plaster of paris from whereever I can get it. For making rocks I mix it kinda thin. 2 parts plaster to 1 1/4 water. This pours easily and doesn’t tend to splash. I use molds made from whatever I have. Several times I’ve made molds from clay I dug out of a ditch. Makes great rocks! Another mold method is crumpled aluminum foil. I also use commercial rock casting molds that I bought from a hobby shop. Use whatever you have. The plaster doesn’t know the difference. Again, regular plaster of paris works great.
Not so brief explanation of Plasters