• Oil pastels present some blending problems.oil pastels image by Ivonne Wierink from Fotolia.com
  
  According to the Outside Shore art website, Pablo Picasso was the first artist to use oil pastels for serious artwork. Oil pastels differ from their chalk pastel counterparts; chalk pastels are made of only pigment and gum, while oil pastels contain pigment, gum, wax and oil. Oil pastels are also more permanent than chalk pastels, since you can easily smudge work done in chalk even after using fixative. Unfortunately, oil pastels don't blend as easily as chalk.
  
  

Colors Won't Blend Correctly

• Depending on what brand oil pastels you're using, results from blending may vary in visually displeasing ways. At the Explore Oil Pastels website, oil pastel artist Robert Sloan gives an example of red and blue refusing to blend into purple. In his example, the red oil pastel is so strong that it overpowers the blue oil pastel every time, resulting in far too much red when Sloan tries to blend or mix. He uses magenta and blue pastels to create the hue he wanted; similarly, to solve a color blending problem, you should experiment on scrap paper or canvas with various color combinations until you get the right color.
  
  

Muddying Pastel Sticks

• When you "paint" with pastels, you frequently use the stick itself instead of an application tool such as a paintbrush. Because of this, color build-up will accrue on the tips of many oil pastel sticks, and the more frequently you use that stick to blend, the more muddy and dingy that stick becomes. To avoid this problem, always clean each oil pastel stick after you've used it on top of another color. Wipe the stick's tip on a stiff paper or a rough cloth. To remove a significant amount of build-up, scrape away at the tip until you reveal the oil pastel's true color. Remember that you aren't totally limited to blending with your stick; if you aren't trying to add color while blending, you can use a variety of tools including pencil erasers, your fingers or wax markers to blend your colors.
  
  

Muddy Colors after Blending

• The temptation to correct mistakes by adding additional layers of color is too much for many artists to resist, often because the technique can be rewarding. However, if you overuse this technique and apply too many layers of color, you'll be punished instead with muddy colors. If you can't apply any more color and actually remove color when you use your oil pastel stick or blending tool, you've definitely over-applied. Your only option is to remove your built-up pastel with a scraping tool such as a palette knife or a razor blade.
  
  

Crumb Control

• Sometimes color will flake away from your oil pastel work; these particles are often referred to as "crumbs." Crumbs appear because you've pressed hard with your pastels or when you've applied a lot of color. Certain brands of oil pastels produce more crumb flake-off than others. Pick up your crumbs with a kneaded eraser or gently wipe them away with a cotton ball or soft rag. Don't leave them on your work; they are essentially a concentrated ball of oil pastel medium and may create a significant mark or smear.