I found this product at the local hobby store over the weekend that I wanted to test out as a painting surface. It’s called “Permastone“ from Activa Products. What attracted me was the claim “ideal casting compound when permanent break-resistant castings are desired. Can be painted with acrylics, oils, watercolors, tempera or any other finish.” It’s sort of like plaster, but sturdier. It cost me about $8.00 dollars. Okay, let’s see how easily I can make a simple panel out of it.
I took a small wood frame with a center space of 8.5 x 5.5 inches to use as a mold. To facilitate removing the panel, I lined the inside with cellophane tape, and taped the frame to a sheet of acrylic glazing. The box says to use a mix of 3 parts powder to 1 part water, so I figure I would need about 12 ounces of powder to fill this center space, and that turned to be accurate.
The powder mixed up easily into a thin paste like consistency that I poured into the center of the frame, wiggling it around a bit to get it to settle evenly in the corners and become level. A few bubbles appeared on the surface, but I figured I would just sand those out later. The instructions said to wait 20 to 30 minutes for it to set, but it was still a bit soft so I gave it another 30 minutes or so.
I took a long palette knife and separated the tape from the plastic sheet. Next I gently pushed the center panel out of the frame from the taped side, and it came out easily in a solid piece. The panel is about 3/8″ thick. If you look closely you might see where the cellophane tape actually left a very slight ridge along the edges, so the Permastone will pick up even the slightest details. Even the wrinkles in the tape were transferred.
The nice surprise was how smooth the back side is that touched on the plastic. It’s like polished marble without any bubbles or imperfections. It could actually be too smooth so I might need to sand it a little. I’m very pleased with how quick this turned out and I like the results. I can improve the process next time by making a better mold. I’m not sure how large a panel I could get out of this without reinforcing it somehow, perhaps with a strong wire grid inside it. One box (28 oz.) should make a panel about 18 to 20 inches square, I’m guessing.
The real test is to see how well it takes paint. I’ll post the results of that later. I’ll let this panel sit for a few more hours before I put any paint on it.