I am making some board and batten shutters and am using four 5-inch boards to assemble each shutter (each board is ¾ x 5). Since they are going to be outside the house and exposed to the elements, I've decided that a quality polyurethane glue is probably the best choice for gluing the boards together. I also want the shutters to be reasonably flat, so I've decide to clamp them from all four sides (the flat surfaces and sides). For the flat surfaces I'm planning on using 2 x 3 boards with carriage bolts on the ends. But what I don't want happening is for those boards to get glued to the shutter.
I originally thought I could prevent that from happening by using wax paper or aluminum foil, but after reading about the properties of polyurethane glue, which will bond just about anything to anything, I'm not sure those are practical choices. I even thought maybe polyethylene garbage bags might be a viable choice. They would probably still get glued to the shutter but could be sanded off afterward and should prevent the polyurethane glue from penetrating to the wooden clamp.
Is this a viable alternative, and does anyone have any better suggestions?
Best Answer
The following is a carry over from a CNC video I saw many moons ago, but have lost the link.
Give the selected adhesive a sacrificial material on which to bond. Your thoughts of using plastic bags aren't far off, but let's add in a layer of adhesive that you can remove.
If you cover the clamping boards with wide painters tape where the glue is going to contact them, you'd be able to remove the tape from the clamping boards leaving the adhesive side exposed and likely mostly shredded.
If it's practical and possible to apply the tape to the shutter boards with the adhesive side pointing at the shutter boards, you may also reduce the amount of cleanup, as the tape will peel off, again possibly in shreds, leaving behind the tape adhesive and the extruded glue from the shutter joins.
You may be able to minimize the extruded glue by taping on one side the shutter boards along the entire length of the join while held together, then bending the taped joint open and applying the glue. When the boards are flattened, it would be easier to wipe off the glue from only one side, then apply more tape to keep that side from bonding to the clamping boards.