Mangroves - pastel and a spray of varnish

from w
The varnish in a spray can isn't quite like the fixative I used to use and the kerosene, or perhaps turps, was a bit too powerful and altered the pastels a bit. Anyway a drawing - A3 size - of mangroves in felt pen was altered a bit with pastels. The paper was a pale orange to start with. I wanted it to be a kind of allover pattern rather than have a special focus on one spot in the picture.

Any suggestions of a better kind of spray to 'set' the pastels so that they don't smudge?