well, I would presume that they would be difficult to see through, unless it was a very thin layer of wax. I recently came upon filing sheets for negs and got a package of 25 7-row sheets for $8. The ones I got are thin plastic but it does the job. 7Dayshop has, (for about two pounds more) have the clear acetate plastic filing. Depending on how much you shoot and develop film, I would say spend the extra two pounds and go for the clear Acetate files.
Good Luck!