I bought 10 cans of Grumbacher Matte (Tuffilm Final Fixative)and I am kicking myself for doing it! Two kids sprayed their pastel portraits done on buff Canson paper with it and it has settled onto to the paper with a white opague/semi transparent film. WHAT is this stuff!!!! (Contents says it contains acetone, xylene) Does anyone know what purpose this substance could possibly be used for if not a transparent fixative that students can layer their pastels, pencils and charcoal?