That is a small jar (6 oz?) filled with a mixture of paint and acrylic medium. After stirring those reds and other colors into the mix, I would up with a really nice gray/tannish color. I can't wait to see what it looks like on a work surface. Any time I'm scraping excess paint and medium from a canvas or panel, I always store that excess away for later use. Now that this jar is filled to the brim, I'll probably use it as a base for one of the large pieces that I'll start work on next week.
I have a thing about getting the most out of whatever materials that I use as possible. If I can find a way to repurpose something, I will, as long is the repurposing isn't something that's going to cause problems in a new work. I did the same thing with oil paints when I used them. I'd save oil paint scrapings in a jar of water for later use. Worked like a charm and the chromatic grays I was able to have were fantastic. Much better than just mixing black and white. The best blacks and grays are those that contain mixtures of other colors. I much prefer "dirty" whites to clean whites, as well.
