Why Choose Oils for a Pastel Underpainting

'Liberty'                18x24            pastel              ©Karen Margulis
purchase here $500

Have you ever wondered what determines the choice of underpainting technique for a pastel painting? Maybe you have wondered why one should bother with an underpainting at all. I love underpaintings for the freedom they give me.

Underpaintings, especially the wet ones are not always predictable or controllable. Wet paint of any type can drip. It can mix and mingle and bloom which often results in those so called happy accidents that we love to embrace.

Oil Stain Underpainting

One of my favorite wet underpainting techniques is to use Oil paint to create an Oil stain effect. 

•  All that is needed is a few tubes of oil paint and some odorless mineral spirits and a brush.  I typically use three colors...Alizarin Crimson, Ultramarine Blue and Cadmium Yellow Medium. I can mix just about any color I need with these three colors. I don't use white as it makes the paint too opaque and the beauty of the oil stain is the transparent quality I can get by thinning the paint with the OMS.

• You need to use sanded paper that can get wet. My favorite is UART any grit. I find I don't even have to mount Uart as it rarely buckles.

• I begin with blocking in the darkest shapes first. I thin my paint with the OMS (I use Gamsol) until it is the consistency of tea. Practice makes perfect. If it is too thin it will resemble a light wash and may be too light.

• If you see your brushstrokes in the paint, the mixture is too THICK. It won't dry very fast and will also fill the tooth of the paper preventing the addition of pastel.

• If done thin enough the underpainting tales about 30 minutes to dry. I put it in the sun or in front of a fan if I am impatient.

close-up detail of the flowers

Why do I like Oil Stain Underpainting the best?  I find the use of the paint and Odorless Mineral Spirits creates the most interesting drips. They resemble roots or spiderwebs. These drips are wonderful in landscapes as they give the suggestion of grasses. I love the head start that it gives me!

TIP:  You only need a small amount of each paint color since you will be thinning it. I always squeeze out too much paint!  I don't like to waste paint so I will often take out extra paper and just do underpaintings that I can use for future paintings.