There are as many ways of oil painting rocks as there are rocks themselves. With that being said, I want to focus on just a few oil painting techniques that will provide a starting place from which other methods can be applied.

Here are the main points:

• Block in a general composition with loose brushwork

• Capture light and shadow with close attention to the value

• Use a palette knife for impasto, building texture and form, and scraping 

• Pull your oil painting together with a brush and palette knife for softening effects and more definition 

Toning Your Canvas

You can tone your canvas first with a light, warm mixture of cadmium yellow, alizarin crimson oil paints, and 50% galkyd oil or gamsol for faster drying time. (Important note: If using Gamsol inside, be sure you have proper ventilation due to the solvent.)

It depends on how warm and vibrant you want your first layer to be. Red iron oxide with cadmium yellow can work alternatively. Just be sure to keep the layer thin so it won’t compete with subsequent colors.

Compositional Sketch

Developing your composition is the most important part of creating the rocks in your oil painting.

First, mix together a relatively cool color using cerulean blue and a little alizarin crimson with enough oil for a semi-transparent blue-purple.

My preferences are Gamblin’s safflower oil or M.Graham’s walnut oil for its lightness and ease of cleaning without solvents. 

Next, using a small round brush, apply a loose line for building random rectangular and oval shapes. The key is to keep the brush flowing for a simple, well-balanced composition. With a towel or dry brush, wipe away any excess paint. 

Creating Lights and Shadows

You can also use this opportunity to fill in the shadow sections of the rocks lightly. The general composition should be established at this point. You will get a better feel for it by standing back about 4 feet and squinting. 

Going back to your palette, you can add more alizarine crimson and cadmium yellow oil paint with a touch of ultramarine blue to intensify the warm sections of the rocks. A small flat or Filbert brush works well for applying loose patches of warm tones around the shadows. 

Building Form and texture 

To begin building form and texture in the rocks, you can thicken some warm areas with a palette knife. As long as you're using very little oil in the mixture, you should be all set for creating “impasto” effects. It is similar to applying frosting on a cake--you don’t want to eat it:)

You can also scrape away sections of the painting to lighten some values. Using the edge of the palette knife will allow for incised lines for ridges on the rock features.

Pulling Everything Together 

To give your rocks more form and definition, you can use a small Filbert brush to smooth the edges between the darker and lighter areas to create a more rounded feel. Conversely, you can create harder edges with your palette knife while also adding darker tones for greater contrast.  

Finally, you can add more texture to your rocks in a few ways:

1.) Using your palette knife to create more fragmented lines

2.) Adding stippling marks in various places with your small round brush

Any other techniques of your own can only enhance the energy of your rock painting even further. The most important thing is having fun and watching things be revealed through your own unique way of painting

To learn more about how to paint, consider enrolling in my fall plein-air painting class or a private session. If you have any questions regarding instruction, please let me know. I hope to see you in the fall if you're not already registered for a class!