DIY Layered Rock Mold

Not having access to good rocks that I can use to make molds from, I decided to "roll my own". There are plenty of articles on how to make rock molds and this article isn't that. I wrote this to show you that you can make your own rock from nothing more then plaster.

To begin, I pour a thin layer of plaster into a Pyrex dish. I use Pyrex as the plaster won't stick to it. After the plaster is dry, I broke it and stacked to make a shale type rock face (using white glue). I repeated this until I had enough plaster “rocks” to play with.

Once I’m happy with the rock face I built using the plaster rocks, I made a latex mold of that. Below is a close-up photo of the mold and master.

Since my layers of plaster had gaps, I sprinkled baking soda into the crevices and used a thin super-glue to set it. Larger spaces were filled with some Sculpey. With this technique, you should be able to create a wide variety of realistic rock formations. 

Here, the mold on top of the plug with a painted casting. The car is 1:50 for reference.

Here is a  close-up of the casting. Not satisfied with the coloring but the layered rock effect I am pretty happy with.