We doubled her recipe and used:
8 tablespoons of baking soda
4 tablespoons of white vinegar
1 teaspoon of light corn syrup (we did not have light corn syrup, we used dark and it did not ruin the colours)
4 tablespoons of corn starch
Food colouring (liquid or gels)
A container to store the paints (we used a mini muffin tin, but you can also use an ice cube tray, plastic cups, or plastic egg carton)
Measure the baking soda into a bowl and add the white vinegar. Mix it together until it stop fizzing. Then add the corn syrup and corn starch and mix together. We then poured the mixture evenly into the muffin tin. I had to hold Bean's hand and guide her so she wouldn't overflow it. Then I let them add a few drops of food colouring to each of them. They made a few different shades of red and pink and orange that all ended up being pretty similar.
So far they have only been drying for 24 hours, but I will leave them for another day before I let them start painting with them :)
After 48 hours they were ready to be used!
I added 1/2 teaspoon of water to each colour, to make it slightly easier for them. I did give them a cup of water to rinse off their paintbrushes in between colours, but they barely used it. They love mixing colours.