It took me a year to figure it out, but if you are mixing tempera colors you should be using cyan/turquoise, magenta and yellow rather than red yellow and blue… So why don’t most places sell gallons of kids paint in magenta and turquoise? For a year we were painting with dingy green and uninspired orange, because I was using the wrong primaries to mix them.
Also, when buying paint from an art store, ‘cleans up with soap and water’, does not mean washable, it means you don’t need turpentine to clean your brushes… Not so swift sometimes mom. Right now we are experimenting with making them ‘washable’ (most of our clothes are paint stained anyway, so I don’t have much faith in this term) using liquid soap. So far EO is less foamy than Dr. Bronner’s. It also makes it peppermint scented! I’ve seen people suggest Ivory Snow detergent, because detergents don’t foam, but it says you aren’t supposed to get it on your skin, so no thanks.