Yoram,
I like your work.
I am not as acknowledgeable about frescoes as you all are.
What I have learned about the use of white is lime that is mixed with water and left to dry and then pulverised again and just used as any other pigment. It just takes some thinking ahead!
I spent a few months in Kibbutz Hatzor a hundred years ago!
Learned a little bit of hebrew.
Myriam