Varnish

Hello- I'm new here- I'd like to ask a question concerning Damar Gloss Varnish. If I have gloss and I want matte-- can I put a certain amount of turpentine in the Gloss varnish to turn it into matte varnish? I usually purchase the small Grumbacher bottles and haven't been able to find matte anywhere I have been looking. I know I read at one time that there is a way to turn gloss into matte but I forgot what to use/how to do it. Thanks