As I grew up, I did a lot of watercolor painting. You may remember the paint sets I used: plastic trays with little oval-shaped cakes of dried paint. You dipped a brush in a cup of water (in my case, an old coffee cup) and swirled it around on top of the color you wanted until it was full of paint. Then you put paint to paper, coloring book or (on one regrettable occasion) the kitchen wall.
It was a simple, stripped-down form of painting, but I loved it. Watercolor painting was a big reason why I became an illustrator. But it also gave me an odd, unhelpful quirk. For years, I thought this was the best way to wet my paint and rinse my paintbrushes:
Ugh! That water may get most of the paint off of a brush, but it's terrible for mixing colors. There's so much pigment floating around in there that you may as well mix all your paints with brown ink. Everything it touches is going to be faded and slightly muddy.
In art school, I learned a new approach, and acquired a couple of indispensable tools:
Meet the wash tub and the mixing jar (or in this case, an old Tupperware canister and a scrubbed out peanut-butter jar), the dynamic duo of color mixing. Here's how they work:
The Wash Bucket
The wash bucket is where you rinse your brushes. Before a brush goes into the mixing jar, it takes a dip in the wash bucket so the mixing water stays clean and your colors stay bright and true. The wash bucket should be big ... as large as will comfortably fit in your sink and on your work table. The more water it holds, the longer it'll take to clog it with pigment. I also prefer a bucket with a wide diameter, so it isn't likely to tip over. I replace this water as soon as it becomes opaque. If you dip a bush into the water and the submerged part disappears, it's time to dump out the water and refill the bucket.
A word of warning: once you use a container for rinsing paint brushes, never EVER use it for storing or serving food. Many pigments contain toxic substances, like cadmium (in red, orange or yellow paint), lead (white), or chromium (green). You probably won't get a fatal dose if you reuse the container, but these substances are biocumulative. That means they stay in your body forever. Consume enough of them over your lifetime and bad things will happen.
If you don't have an old Tupperware canister in your kitchen, pick up a paint mixing tub from your local hardware store. They're cheap, stable and relatively durable.
The Mixing Jar
The water in the mixing jar is only for diluting paint or mixing colors. I never (with one exception) dip a loaded brush into this container. So the water stays clean, and my colors stay bright and reliable.
Here's the exception, when I'm diluting a color I may need several brushloads of clean water before the paint reaches the right consistency. If I rinse the brush off in the wash bucket before every brushload, I'll waste a lot of paint. So in this case I do dip a paint-filled brush into the mixing jar. There's a trick to it. Instead of swishing the brush around, like I do when I'm rinsing it, I dip it straight in and straight out, without any side-to-side movement. If I'm careful, it leaves just a tiny ring of color on the surface of the water. And the rest stays relatively clear.
I like a clear jar for this. It lets me see just how clean the water is. Once again, low and wide is better than tall and thin. Because I change the water as soon as it gets cloudy or takes on a noticeable tint, I prefer to use a smaller jar. That makes the changes faster.