Ok may have found it "mask layer"

I hope “may have found it” meant you did actually find it, Vicki, but it does sound as though you did! When you paint on a mask layer, white reveals (full opacity) and black conceals (no opacity) whilst grey gives you something in between (partial opacity).

By the way, if someone else had answered your question they would have supplied their answer as a reply to your original post. When you’re able to supply the answer yourself, it’s clearer to everyone if you do the same: leave your original post unedited and put your solution in a new post.