I tried to glue two pieces of 2" thick foam together. I used Loktite PL foamboard adhesive and weighted it down with full paint cans. Previously I found out that if it is applied too thin, it doesn’t stick well, or the drying process causes warpage.
Either too thin, warpage, or not enough weight and one side was not glued from the edge to at least 4" inward.
I had some PL 230 caulk, which had previously worked well, but not nearly as much as I thought and ran out midstream. I rummaged around and found some GE silicone caulk (expired 2011) I shoved that in the gap the best I could with a putty knife and this time clamped the two pieces together.
19 hours later the caulk is as wet as when I put it on. Drying time was supposed to be 3 hours, tackiness was supposed to be gone in 30 min. A google search says this is a common problem with expired silicon caulk, one person saying it had not dried in 3 days.
Cleaning the bad caulk is not going to be easy, if it is possible at all, because the two pieces are partially glued together.
I’d guess that this product would be more suitable than caulk for gluing foam. While many modellers use caulk to hold track in place, it seems to me to be a rather tenuous bond: good, I suppose, for those wanting to later move or remove track.
However, the primary purpose of caulk is to seal cracks. That it functions at all as an adhesive is, to me, with no experience using it as such, rather surprising.
While there’s currently only one small area on my layout where foam was used (an incline for the service track, for delivery of coal and sand, to my Tichy coaling tower) I used LePage’s PL 300, which is made expressly for use with foam, to affix it to the plywood surface of the layout in that area…
The instructions suggest applying it to one of the mating surfaces, then pressing the other into place, and then immediately removing that piece to allow the adhesive to “vent” for 2-5 minutes. After that time, the piece is to be firmly pressed back into place. I placed some weight atop the assembly and left it in place for the suggested 24 hours, and nothing is loose or moveable.
I’ll use the same method when I add some foam as scenic features elsewhere on the layout’s upper level, as all of that area is plywood.
Many times when mating 2 pieces of foam, there isn’t enough air to allow to dry and cure in any short period of time. I have found that spreading with a notched trowel can help as it allows a substantial amount of air to dry. Had one section of scenery that the 1 1/2" foam wouldn’t bond for over a week, it was adheared with DAP Alex plus also. I have had better luck bonding foam using ceramic tile mastic, Quick tack and dried in a couple hours for a suffiecient hold to continue.
I used PL300 and I pressed the foam into place and there was no way I was pulling that stuff up to vent, it wouldn’t let me. So I left it in place and it is there for good. I made darn sure it was in the right spot the first time as my tummy told me it wasn’t coming back up. All my foam is held down with PL300 except where I layered foam for mountains, there I used caulk as it lets them wiggle a bit if bumped, thus avoiding damage.
I find a lot of stuff in tubes does not age well once open. I threw a lot out yesterday as I was doing house repairs. Just the cost of doing business I guess.
Maybe it was PL300 that I used first? I’ll have to look in the trash. In my case the stuff on the edges was still wet, so venting wasn’t an issue. The smell of venting is vinegarish.
Like our Forum electrical mysteries, you don’t get all the facts up front. The two 2" foam pieces were 24 x 60" That’s a lot of nail polish. I did not try it, because it would take more than my wife would be willing to spare.
On top of that I glued a 3/4" piece that was U shaped with the bottom of the U was parallel to the long side |______|
It also had the same problem of not sticking along the long edge. I hit both gapping seams with a garden hose and poked at the mating surfaces with a putty knife. The 3/4’ piece I was able to remove. Had it stuck 100% with the PL 300, I think that would have been perfectly acceptable as the foam isn’t subject to any shear forces, it just has to sit there. But it didn’t stick.
Ken Patterson (search youtube What’s Neat) is a foamaholic. He uses gorilla glue, which is water activated and Great Stuff, injectable foam to glue foam. He has a metal nozzle he uses for the later.
Gorrilla glue is water activated and expands. I already had the water so I filled the gap a couple times, with the foam sheet perpendicular to the ground and clamped the two 2" pieces together, where they hadn’t previously sealed. That worked![:)] FYI Gorilla glue expands, not nearly as much as the spray foams.
The 3/4" piece has a lot of dried PL300. I didn’t tell you that side was painted. It pulls off, taking the paint, but not the underlying foam, like skin after a bad sunburn. On one level that is extremely satisfying, but it is also tedious. I may just cut a new piece of foam.
Patterson, I believe, would use the Great Stuff spray foam to glue large sections of foam. I need
I took a year of organic chemistry, but I didn’t want to be rude to someone who was trying to help. OTOH I could easily have bought a quart of it at ACE hardware.
That’s how I found this stuff. Someone was doing a demonstration, and it looked great. I bought a quart and did some test bonding. And it WORKED great. So I used it.
You can apply it with a paint brush. And it doesn’t stink.
It’s been a few years. My recollection was to put weights on the pieces overnight, and done.
Silicone caulk goes bad, very bad. I myself made the mistake on a home improvement project, even though I used to work in the trades I had always used siliconized cauk (basicaly regular caulk with an additive so it remains more flexable but is still water clean up) but this was for outside stuff was and I had a tube lying around, badddddddddd mistake.
