The usual method to make impression of stomata is with petroleum jelly (like Vaseline). However, I notice that after the process the area of the leaf covered with petroleum jelly withers quite a lot. Petroleum jelly seems to absorb the water from the leaf and wither it before the jelly manages to dry. I am concerned whether this will cause the impression of the stomata not accurate, like in case we want to count the number of open stomata. Is there any other alternative to petroleum jelly that can do the job without drying out the leaf?