Richeson 9-Color Tempera Cake Set

This is just a warning, I absolutely LOVE this product. Unfortunately I had to learn the hard way when these are left with water in them they spoil. I teach almost 900 3rd and 4th graders in a week so they are constantly adding water. Did not notice it until the third week of painting. First it was the white then the black, the smell is horrible like spoiled milk. Yes, I did go over the proper use of this paint with students. For clean water I had small spray bottles at each table which worked great at keeping the cakes clean and moist but of course every 30 min a new class would come in and want to spray their tray. Hated at the end of the day to dry trays because so much paint was wasted. Maybe next years paint project I will just stress MORE the importance of not putting much water. :)