I ham having some trouble and am hoping the art community can help. I paint mountainscapes, which by its nature uses a lot of pure white. I paint oil on canvas but I use palette knives so I need the paint to be elastic as the paint layers are thick. The trouble I am having is that after 6 months, the white areas are yellowing significantly. I have been using Georgian oil Titanium white. If I use Zinc, its too transparent and cracks with the amount of paint I need to use. Can anyone help? Do I need to mix the titanium white with anything to stop the discolouration? Will a retouching varnish followed by a UV satin varnish stop this problem or am I doomed to yellow snow...?