I use underpainting all the time with soft pastel. Now that my focus in on Oil Pastel, I find nothing on the use of underpaintings with this medium. Ergo, weeks of testing and trying different ways of using an underpainting. First of all-Why?
Using an underpainting is the prerogative of the artist. Depending on what outcome you have set your mind to, it may very well be a smart move. For oil pastel, there are many ways of accomplishing this, but only a few I would recommend for artists of any level of expertise. My reasons for using an underpainting are to set the tonal values and keeping the painting fresh. Especially when working in layers.
1. Setting the tonal values. Setting the darks and shadowy areas from the light and mid-ranges.
2. Pre-drawings-setting the pace. Establish a foundation
3. Setting the style of the painting. Visually, colors change when placed near or on top of other colors. Sets the mood of the piece.
4. Contrasting colors. Always a good choice in underpaintings. If the finished painting is primarily cool, then use a warm underpainting. Vice Verse, if the finished painting is warm, then use a cool underpainting. Local color-equally as beneficial.
5. To quickly eliminate that over-bearing, blank canvas. Some of my students will tone the paper prior to the exercise, just to get rid of the stark whiteness. Puts the artist at ease.
6. Develop contrasts before using color.
7. Sketching the composition. Learning before using the oil pastels if the composition you have chosen will actually work. Visual recon. Giving you a path to follow.
There are many other reasons for using underpaintings but this is enough for now.
Using an underpainting does not change your oil pastel into a mixed medium. You are only preparing the substrate. You can use any medium for underpaintings with just a bit of forethought. I prefer only three.
1.Watersoluble oil pastel,
2. Watercolor, with contrasting colors. Look at how the reds and greens are deepened.
