Casting and adding stones to a Diorama

Casting and adding plaster rocks and cliffs are a great way to make a diorama look realistic. It takes a little bit of skill to cast and paint the rocks but is not that hard. This tutorial will show you how to do it. The following two photos show a diorama with cast rocks in it. They look great and are particular nice as the sides of cliffs. And they look fantastic for rocky outcroppings.

Cast rocks on a diorama

cast rocks on a diorama

How to do it

casting rocks materials You need a few materials to cast plaster rocks. They are shown in the picture here. Lightweight Hydrocal, Rubber molds, measuring cup, water, a spray bottle and a little bit of dishwashing detergent.

The spray bottle has 6 ounces of water and two drops of liquid soap or dishwashing soap in it. This will prevent bubbles from forming and will help the rock come out of the mold.

Side Note: These rock molds are great and readily purchased from online retailers or hobby shops. You can also make your own molds by using Latex rubber. I have done this, it works real well and I will be doing a tutorial on how to do that.

Lightweight Hydrocal - Rock Mold, Strata Stone -

Prepare your mold by supporting it with pieces of wood or anything else. You don't want it to sag when the hydrocal is added. Tape it to pieces of wood if necessary. Then spray a thin coat of the soapy water all inside the mold.

Now pour the mixed hydrocal right into the molds. You don't have to be real neat with it because you can trim it and manipulate it later. Now let it for about an hour.

When pouring the rocks you want to be gentle and go slow. Stir it gently. You don't want too many bubbles to form they will look unnatural.

Now you can remove the cast rocks by gently bending the mold until they release. If you break a rock it is not a big deal. The breakage lines on the two halves are perfect fits and you can glue them right back together. They glue together so perfectly that you can't even tell it was broken. Use some little tools, some sand paper or a little hobby knife to trim off the rough cast edges.

Here is a video that shows exactly how I cast these rocks. Below this video I continue with the tutorial and have another video that show you how to paint them so they look great.

Painting and adding details to your stones

The basic process of painting the rocks for your diorama uses the washing method. This is where you use a couple of basic colors like black and grey and you wash the stones with a very dilute version of these colors. Then you go back and do a second layer of highlighting with a more solid and less wet paint.

This video shows you the whole technique