I am to the point of building my scenery around my elevated road bed. I’m using 3/4" extruded foam, because that is all that I can find in central Alabama. What is the best way to layer and glue the foam together? Do I need to pull off the cellophane wrap or backing on the foam? I’m just looking for any general tips or advice that will help me make this a painless process.
David
I’m not familiar with the backing??? Most are using walmart or similar cheap paintable latex caulking in the color of your choice.
The foam you have is the type with foil on both sides am I correct on that? You can use this just fine it is a bit more work but it will work. As stated in the above post you can use latex caulk. As far as shaping the foam, the foil presents a problem that you will have a hard time shaping it with a hot wire cutter. Cutting it with a utility knife will work fine since it is thinner material. I have shaped sharp edges using a heat gun, you can soften the edges using the heat gun and use a small masonary trowl to round them or push them down, just be careful with the heat gun. Fire could happen if you get the foam to hot on the edges.
The foam I’m using is from Lowes or Home Depot and is 3/4"x4’x8’. It dose not have a faoil backing, only a thin plastic film that helps hold the serface together better. It peels off easy and makes carving easyer when it is not on.
David
Yes, you don’t want that plastic bluish or whatever film in place…peel it off. Then, with a cheap acrylic latex caulk, nothing expensive, spread four or five or six wavy thin lines of the caulk along the surface to be glued, and spread it flat and thin, like a thick layer of fresh paint, no thicker, and then press the foam to it. Place several stacks of magazines or boards with some soup tins across the foam surface (carefully! Don’t drop anything.) on top of the foam and leave it for several hours.
I have heard about putting weight on it while it dries. Is ther a chance of the foam warping? I might have some tight places where I won’t be able to put a large or heavy object on it. There will be a lot of contours and elevation changes to work around. I was planning on using “Foamboard Adhesive” that I picked up a couple of months ago.
If I open the tube and don’t use it all, will I last till the next weekend when I get back to working with it again. In the past I plug the tip with a golf tee when using silicone. I have been cutting out as much of the foam as I can making my 3-D puzzle. When I’m ready, I’ll have a hayday glueing down my foam.
David
The foam will warp if it isn’t being glued to a planar surface, or if the surface has something foreign left behind, like a small piece of wood. If your plywood is very close to planar, and is itself supported well below it so it can’t sag appreciably, the foam will merely conform to the flatness of the plywood. The weight ensures uniform adhesion across the surfaces being glued together.
I can’t answer about the “foamboard adhesive”, but if it says safe for styrofoam/polystyrene foams, it will be okay.
If you only use some of tube contents, wrap the open tip with cling wrap and an elastic. When I planned to use the caulk within several days or a couple of weeks, I just shoved the sharp nib into a chunk of waste styrofoam…that worked quite well.
As a tip, if you are going to be doing a lot of finer shaping using a wire brush or sanding blocks to get a smooth contour, your caulking near the front edges that you are refining will get in the way…it doesn’t sand or scour well. So, think ahead a bit as you are squeezing and spreading your beads of caulking or adhesive…don’t get lots of it close to the leading edges where you will soon be working.
Whenever I glue sheets of foam together, I always set a weight on it. I have also found a good source of sand to use in landscaping and ballasting; those sand tubes that you can find in the garden section at WalMart. I pour the sand into an empty kitty litter tub. I use a medium strainer to remove the small pebbles from the sand.
I use 1 1/2 inch drywall screws in assembling my layout benchwork. After I use a tube of caulk, I stick a screw in the nozzle. When I’m ready to use it again, I just pull out the screw, and it pulls the hardened plug out of the nozzle.
David, the foam won’t warp. You can hold it together temporarily with HAND DRIVEN deck screws. Larger diameter holds better. Go easy, stop when the head touches and they will hold it until the glue dries. Then remove the screws.
Good luck,
Karl
I use yellow carpenter’s glue for foam. Never had a problem. I don’t use the waterproof type, though, so I can disassemble when I want to change the terrain. I use Dow blue foam in 1" and 2" sheets. Never saw any with a film on the surface, either pink or blue.
Elmers carpenter’s glue here too, though I dilute it about 50/50 just to make it cover more area.
Works great, and is a lot cheaper than caulk, which is overkill imo.
I’ve also used Liquid Nails with great results. Just plain Liquid Nails; doesn’t have to be Liquid Nails for Projects, or for Foam, etc.
I use the Dow extruded polystyrene, AKA blue board and use a hot melt glue gun. Works instantly.