Using Hot Melt Adhesive
Hot melt adhesive... when to use it and when not
I have grown fond of hot melt adhesive. Fast setting is its most noble attribute. However, it is not an especially strong adhesive and is intended to be applied somewhat thickly. This makes it generally unsuitable for quality finish woodworking. I have seen inexpensive cabinets literally fall apart because they were assembled with hot melt.
But this is not to take away from its versatility and usability. It is employed extensively in craft making, artificial flower arranging, in manufacturing to seal cardboard boxes and in some product assembly. Hot melt glues are available in high and low temperature formulations.
It is great when used as a secondary adhesive, to hold items together for screwing or primary gluing (see the Famous Glue Trick).
There are many types of hot melt adhesives manufactured for professional and industrial use that far exceed the strength and durability of the typical hardware/craft store products. The seaming tape that carpet installers use is glued with a special hot melt adhesive and, as I'm sure you know, carpet seams are about as permanent as anything in this life!
Adhesive Technologies, SDA/Craft Technologies, H.B. Fuller and 3M are all major manufacturers of hot melt glues, and their products are widely available in hardware, home and craft stores.
Hot glue tips and tricks...
Hot glue guns are simple to use. Plug the gun in, allow it time to heat up, and then squeeze the trigger to apply the adhesive. Melted glue very hot and will burn the skin instantly, so be careful! Press the parts to be glued together and hold till set, literally seconds for thin applications... a few more seconds for thicker applications.
Sometimes the glue stick will not feed properly and may need a push. Feeding too much glue at once will cause the gun's mechanism to slip against the stick till more of the glue stick melts. Also, once a stick is almost used up the gun may need a second stick to push the first through.
Different hot melt glues have different setting times, and this will determine its proper uses.
Some hot melt glues dry almost instantly and are best for situations where repositioning of the parts is unlikely and speed is important, such as in many craft projects. On the other hand, slower hardening glues are better when it may take a little time to position the parts, such as when installing cleats for drywall repairs. In my own work, the only hot melt adhesive I used was a slow-setting type. I realized that each time I changed the glue, I had to waste whatever was remaining of the stick I started. Waste not, want not!
Most importantly, hot melt glue is designed to be applied thickly and seems to stick best when it is not squeezed too thin. That means it can't be used where the tolerances are tight, such as in fine woodworking. No problem, since there are stronger, better glues designed for woodworking, such as polyurethane glue or good old wood glue, that allow the repositioning time needed to apply clamps.