I wouldn't have a clue either. This site here says "Cover the plan material with wax paper to use tissue covering. With Japanese tissue, put the glossy side down over the plans, and glue the balsa sticks to the tissue. You should still be able to see the plans through the tissue." Seems like they're saying the dull side is the side glued to the model. http://customers.hbci.com/~bkuhl/building_tips.htm
BTW if I ever do start covering with tissue, I've amassed a nice collection of it over the years. I keep thinking about building a rubber FF model for once.
This is a paragraph from the book Peanut Power By Bill Hannan. It is the only thing on the subject I could find in print.
" Some brands of tissue are relatively shiny on one side. Opinions differ as to whether the shiny side should face out or in on the part being covered. The main thing is that it should all be uniform, whichever choice you decide to make.
For me personally its shiny side into the piece being covered.
Esaki tissue, and some others, are calendared, that is shiny on one side. For modeling use, the shiny side goes out. It takes a finish better whether clear or colored. If you want a matt finish, use a matt paint or clearcoat.
Thank You all for the answers. Shinny side out it is.
The medium Navy Blue I plan to cover the Hellcat is definitely shinny on one side. I did a little work on the Rufe today instead. I will start covering the Cat tomorrow.