05-27-2009, 11:27 AM
At the modular club <!-- m --><a class="postlink" href="http://www.hotrak.ca">http://www.hotrak.ca</a><!-- m --> we build with foam, as well as use it for landscaping like Will. We have had better success with the Gorilla Glue polyurethane-type adhesives than the white or (yellow) carpenters' PVA-type glues.
The reason for this is (as alluded to by Herc Driver) that the PVA-types require air exposure to cure, while the polyurethane ones need only a bit of moisture. So where the glue is sandwiched between layers of foam it will dry around the edges, impeding the centre from drying completely. The Gorilla Glue cures without air, so this is not a problem. In applications like Will's, where the benchwork is permanent and does not move, you can wait weeks for the glue to dry. With modules, you want to be able to pick them up and move them in short order - not a good idea if the glue is not dry...
One other advantage of the polyurethane glue is that it can be cut with the tools used on the foam itself. Sometimes the PVA glues will harden to the point where it is hard to cut through. One caveat for polyurethane - it will expand slightly, so be sure that your pieces are aligned properly before the glue sets completely...!
Lastly, a tool that I like to use for "carving" is a wire brush - just scrub away the bits of foam you do not want. Makes a heck of a mess, but since they are available in different sizes you can find one for almost every need.
Andrew
The reason for this is (as alluded to by Herc Driver) that the PVA-types require air exposure to cure, while the polyurethane ones need only a bit of moisture. So where the glue is sandwiched between layers of foam it will dry around the edges, impeding the centre from drying completely. The Gorilla Glue cures without air, so this is not a problem. In applications like Will's, where the benchwork is permanent and does not move, you can wait weeks for the glue to dry. With modules, you want to be able to pick them up and move them in short order - not a good idea if the glue is not dry...
One other advantage of the polyurethane glue is that it can be cut with the tools used on the foam itself. Sometimes the PVA glues will harden to the point where it is hard to cut through. One caveat for polyurethane - it will expand slightly, so be sure that your pieces are aligned properly before the glue sets completely...!
Lastly, a tool that I like to use for "carving" is a wire brush - just scrub away the bits of foam you do not want. Makes a heck of a mess, but since they are available in different sizes you can find one for almost every need.
Andrew