Hi, I teach private art lesson in groups of eight in Canada. I think you can easily only have 3 sets. Two students can share. The larger cakes can last a long while. I don’t know how much you use paint, the size of the paper or how many classes. But anywhere from six months to 16 months, is my best guess. They can be used very similarly to water color. Just give your students pallets to put the color in and add water. As water sits on the cakes the color deepens. So for even light washes use a pallet, or order an extra tray for students to leave the concentration of color they want. Just add water with a spray bottle. Like watercolor paints, more pigment can be added to make gradations or lighten again with more water. The colors do mix, just use the another tray or pallet for that as well. Unlike watercolor it can have full coverage, depending on the brand. Just moisten with the spray bottle and stir untill the water is opaque. As was mentioned you can do this in advance so it’s ready for the students by letting some water sits on the cakes for at least 30 minutes. Tempera paint in this form it’s hard to blend directly when opaque. But once it’s dry students can take a clean brush with water and blend between two colors where they meet. The best brushes to use with this paint I found is the traditional Chinese bamboo brushes. Otherwise water color brushes do the job.

What we order are simply called “Tempera cakes” from the Sax/ School Specialty catalog. One big thing your comparison left out is cost. We buy the refill cakes at around $3/6 of the same color, versus the Alphacolor refill which,seem,to,be,2.85 each?

Pro and con for the tempera cakes in trays of 6 that we use : the cakes last a VERY long time, but they become impossible to remove from the tray! These round cakes are also just the right size for muffin tins or individual applesauce cups ( good for when we want to limit color choices, like trying a blue wash over oil pastels or crayons.)

As others mentioned, I use a spray bottle to wept the cakes before use, and I often swirl the paint brush around to get the water,really filled with color. I sometimes,out,up a sign which shows the steps “Paint, Paper, Water” . Early experimenters are definitely more interested in the color mixing than getting anything down on paper!