our professor's old recipe for matte thinner for grisaille “wax emulsion”

Lucie Vergnon, 
Hey! This is white spirit. In Russia, manufacturers of art supplies sell it under the name thinner number 2, unfortunately I don’t know if this is the case in other countries, thanks for your question, I’ll edit it in the post to make it clearer for everyone))

ksy elf, Thank you for your quick answer... It's cristal cristal clear for me now...  Thank you so much (from France :) )