This is a short article on how I colored the rock on m layout. I’ve come to understand that there are as many ways to color rock as there are colors, so don’t take this as the only solution, but I think it works pretty well.

The goal for my rocks was to replicate the color, textures, and tone of Western Pennsylvania rocks. Mostly sandstone and limestone, but with heavy staining from sulfur and other run off from coal mines and mining activity.

To start off, you will need some paint, something to mix the paint in, and a brush. For this project, I’ve used water based acrylic paints, a painter’s palette, and a 1/4″ square brush. The base colors are:

  • Burnt Umber
  • Raw Umber
  • Raw Sienna

I’ve used other colors for other purposes, such as Green, Blue, Yellow, and Red, but these are the base for all rock work I’ve done. Here’s a picture of the materials.

Rock Painting Materials

First start by putting a little paint in a small container.

Add the paint

Then add a fair amount of water to the paint. The amount of water determines how transparent the paint will be when applied. More water, the more transparent. The less water, the more opaque. I like a medium transparency, then I can built up the color that I want. However, some people use the paint straight without any thinning.

Add Water

Once the water is in, using the brush, draw the paint to one side of the well. Mix the paint with the water by pulling it repetitively to one side. By pulling to one side, you know where the heaviest concentration of paint is – if you want a lighter, more transparent touch, use the paint on the opposite; thicker more opaque washes are applied by using the paint closest to side the paint was pulled towards.

Mix by pulling to one side

Clean your brush in fresh water between each well to ensure the colors remain pure.

After all the colors are mixed, start painting the rocks by adding some highlights. I generally highlight the undersides and cracks using raw umber as show below.

Highlight using raw umber

I then blend in the undercuts and cracks using brunt umber.

Blend with burnt umber

Following the initial blending along the edges of the undercuts, I usually blend using burnt sienna and other colors as the feeling strikes me.

Blend with burnt sienna and umbers.

Burnt sienna is great for that sulfur stained look I’m used to seeing in W. PA. I think raw umber and burnt umber make really nice generic rock work for the north east US, with highlights of black and burnt sienna.

Blend colors randomly

A touch of green works to simulate moss or mold and the slightest touch of black help darken up burnt sienna and other colors to make a wide array of in-between colors. Here are a number of different rocks all made from the 3 base colors and black.

Rock samples made using base colors and black

For those who have not attempted coloring rocks before, I found it help to start on a sample piece and become comfortable with the colors, washing, transparencies, and shading. After a few test rocks, I was comfortable enough to color all my rock work in one sitting. I’m pleased with how they turned out and will continue to use this technique in the future.

Cut out rock work


Rocks over tunnel

I think you will find this technique straightforward, easy, and fun. Best of luck!