On one of my snow days off, I tried my hand at painting with watercolor, baking soda and vinegar. I saw this on Pinterest and was bored enough to give it a whirl. It's the kind of thing you do to entertain your young children, but why not? I was pretty much alone with nothing else to do except shovel snow. First, you put a couple of spoons of baking soda in a cup and then you add about a quarter cup of water. Then you can add either liquid watercolor or food dye. I had a 20-year-old box of Pentel tube watercolors so I used them.

Then I began painting, the paint is kind of thick and needs stirring.

I made three different pictures on watercolor paper, one with squiggly lines, one poured, one squares. I also drew a little in my sketchbook. Then I used a dropper to add the vinegar.

Hisssssss, it makes a cool sound.

It was fun, but eventually, all the colors ran together. I guess if I did it again I might tape the paper to a board so that I could pick it up and swirl it around more.

Here is a detail. Hours later I could drop more vinegar on it, it would fizz some more. The sketchbook was the least exciting, probably because the paper is thinner. It is definitely about the process instead of the product. 

I highly recommend doing this if you are 4 or 5 years old.