I have an Autumn Blaze maple, coming out of winter in its third year. Yesterday I noticed that the south facing side looks like it had been spray varnished. It appeared to be very wet. When I ran my hand up its surface, it was as smooth as glass and dry. It looks wet in the way the side of a tree looks when it has received rain from one direction, due to wind. The bark on the north side of the tree is the normal, smooth light grey in appearance.

There are no drip marks, like from running sap. So I am wondering: can sap, activated by being on the sun exposed side of the tree, exude through the bark, much like sweat through a humans skin? I did find a couple of areas of the "wet look" that were slightly tacky.

ps: I just looked closer at picture two, and it does appear to look like drip marks. Everything else is smooth and consistent, as if it came out of a spray can.