Summary of the information you gave in the evaluation form:
One group mixed the chalk with water and put in the (acrylic) colour. The paint then became too fluid, so more chalk was needed. Then we had to add more colour, and the paint became too fluid again. It took some time to get the right consistence. The final paint had a wonderful thick consistence and looks beautifully natural. It dries really quick, and the colour changes in the process.
Another group mixed chalk, water, and colorant from pastel sticks. Needed a lot of chalk to get desired consistency. This paint did not cover very well.
No one tried chalk and larger amounts of dry pigment. This is probably the best option, but will definitely create a paint that will be very soft and dull (not shiny at all).
The casein paint was the hardest one to make, because of the hot water and quite complex process. It makes a nice consistency, but it smells really bad when the casein reacts with the antler salt. Easy and great appearance in use.
One of the groups made a casein paint that became very lumpy. However, even this paint turned out really nice when it dried, with a shiny varnish-like look.
The egg tempera was quite easy to make. The hardest part (for kids) is probably to separate the egg yolk from the white. Nice paint to use, and looks good when dry pigment is used.
It seems to work to mix acrylic paint with yolk.
None of the groups were very successful with this recipe.
We did not evaluate this one, but observing the process makes it safe that this was fairly successful. The paint takes some time to make, but became easy to useand the result looked really nice. The iron oxide pigment (see how it can be made) made the paint cover really well.