Been thinking about sticky tape. You know the stuff, duct, scotch, masking…tape. How’s that stuff work? You start with a strip of plastic or paper or cloth, you coat one side with glue and then you roll it all up into a little wheel. That’s the easy part I guess. Because when you dispense the tape how come the glue is only on one side and the other side is fresh as a daisy? How come the glue, which readily adheres to the strip material, doesn’t also glom onto the clean side when it’s all rolled up? Why is that?
Because the surface of the backing is not the same on both sides. One side has a surface to help the adhesive stick to it and the other side has a surface that helps the adhesive not stick to it. Also, the adhesives themselves can have different properties when applied than after they have cooled or dried or whatever.
look at a sheet of decals.
The glue would stick to both sides at the time it’s applied. It has to be heated before it’s rolled up so that it won’t stick to both sides.
Am I the only one who read this in a 1950s Government Service film voice? 
(Or was that intentional?)
The how’s and why’s of stickiness are, oddly enough, on the cutting edge of science and the subject of much debate and research at the moment.