[I am seeking a material to create smooth transitions from the surface of one foamboard panel to another across slightly less than level margins.] [*-)]
Ok I thought I had this figured out. I wanted a caulk to use on the margins of my 2’by8’ extruded polystyrene foamboard that would not shrink like regular latex acrylic caulk. So I used more expensive non-srhinking GE Silicone II. It does not adhere. Well, it does sit there nice and flat and clear and shiny and does smooth over the irregular margins nicely. But a little rub with the finger and the whole area begins to lift with not a hint of adhesion to the surface of the foamboard. I’m not sure I want to leave something so tenuous under my cork roadbed where it crosses and recrosses the margins so often.
Acrylic latex adheres a little better, but I found it too will rub off rather with a bit more thumb pressure leaving no mark on the foamboard to show any adhesion.
Is this a catch-22 ? I suppose any glue/caulk that really would adhere to foamboard would also be one that begins to eat into the surface. This might counter-act my wishes to produce a smooth transition from one panel to another.
What do contractors use to glue this stuff?
I haven’t tried the Dap spackle or other drywal type muds yet. Maybe they will hold better.
I have not had any problem with latex caulk sticking to extruded foam insulation. Are you usign the pink or the blue? Does it have the plastic film on it? If it does, are you removing said plastic film? I use the pink and it has no film. If latex caulk did not stick to it, the vurves on my layout would unsnap and straighten out, all my roadbed would peel off, and the two layers (I use two layers of 2" foam for my base) would come apart at the slightest touch. I’ve also glued Tortoise machiones to the bottom of the foam with some latex caulk, and to get it off I had to pusha nd pull so hard I thought it would break the Tortoise. When it did let go, it was actually the foam that came apart. I have an ‘oops’ where I thought I released all pressure fromt he caulk gun but some dripped out and set up before I caught it. Either it will be a small hump in the ground cover or a depression if I did it out - it won;t simply flick off and leave the foam unmarked.
You may not be allowing sufficient time for things to set up fully. For the track and roadbed, (granted the track is plastic on top of cork, not directly to the foamboard, but the roadbed is getting glued tot he foam), I keep things pinned for at least a full 24 hours even thought he caulk has suppsoedly ‘set’ and turned clear in just a few hours. For foam to foam, I keep weight on it for 2 days at least, since there is little air penetration it takes a LONG time to set up.
I have used adhesive caulk, hot glue, liquid nails, and yellow carpenters glue on foam insulation board, and haven’t had a bit of trouble with anything not sticking (yellow glue takes about 24 hrs to cure owing to the lack of air, but it does work).
Some brands of foam come with a plastic film on the surface. Are you sure you removed this?
Silicone caulk is for bathtubs. It is one of the few materials that has very little use for model railroading. It likes to stick to itself more than the surfaces you apply it to, so very often you can easily pull it off, or rub it off, like you’ve done. Besides that, you can’t paint it. Once it cures, paint won’t adhere to it.
Latex caulk is what you want here. I use Liquid Nails for projects, which doesn’t shrink much, and it will adhere to the pink foam without eating into it like some solvent-based glues. Plaster materials will work, too, although they will crack when flexed. However, if your layout base is flexing after you’ve got track down, you need to examine your benchwork, because it shouldn’t do that.
One thing I like about foam roadbed, like the Woodland Scenics stuff, is that it can compress easily and smooth the transition when you’ve got a couple of pieces of slightly mis-aligned foamboard.
Yes, I will be removing the silicone. It will not be difficult.
The foamboard I use is Owens Corning Celfort 300 (It may be called Foamular 300 in the USA). It is pinkish, has no plastic and yes, latex caulk does not actually stick to it well.
Although I too have used the basic latex caulk to glue it down to 1/4 inch plywood and it has stayed “glued” after I have left it clamped/weighted for 24 to 72 hours, I think you will find that it will actually still rub off the foamboard with thumb pressure.
Try it. You will have some difficulty if the layer of caulk is thick, but if you rub anywhere where this is a thinner smear you will find that you can peel it / roll it off with your thumb. Now this will also be the case under the thick layers that seem to be glued firmly, but, of course, the adhesion at the boundary down under the thick layer is still just as tenuous as under the thin smear.
I think. I don’t mind being corrected, though.
However it sticks well enough for us hobbiests to continue to use it on the panels and under the cork roadbed etc. Of course you don’t ever want to let it get wet unless you intend to unglue the panel.
As for my uneven boundaries, I think I will move on to some other products and experiment.
About the only thing that DDIN’T work for me was Liquid Nails for foamboard. Before I built my previous layout, I picked up two 2x8 sheets of foam, conencted them via the tongue and grove, and got some wood to fasten underneath to hold it together to make a simple 4x8 test table. I used the Liquid Nails for foamboard, or whatever, one that would not eat the foam, then weighted it all down. A week later when I took the weights off and lifted it up, it all fell apart.
I also had to attach a fixture in the bathroom to the tile. I got the liquid nails product recommended for that. It took 2 weeks to dry and finally hold the fixture to the tile. These experiences pretty much have soured me on anything with the Liquid Nails brand. I’ll stick to latex caulk and yellow glue - the yellow glue holds my foam to the wood and I also use it to glue up the wood parts of the benchwork (except for the legs and braces, which bolt on in case I ever need to move again)
I’m sure the gentlemen of the forum will allow me to correct myself at the risk of excessive posting on this topic:
After overnight experimentation what I find is simply that you get what you pay for.
The basic DAP acrylic latex caulk does not stick very well to foamboard, although it does a passable job on plywood. It is only $1.90 / tube where I live.
The next DAP acrylic latex caulk up the product line. It is $4.00 a tube. does stick well to foamboard. It also comes in clear which is what I have always used for the corkroad bed to plywood and track to cork etc. etc. The formulations must be significantly different…
However as I needed 4 dozen tubes I got the basic one at first. Now I find I can use the clear one for my margins as I need fewer tubes for that.
New to the forum, thought I would provide some information from personal experience. On my last N scale layout, which was 2" pink foam over a wood frame, I used Locktite Power Grab Foamboard adhesive. Glued foam to 1x4’s, foam to foam, cork to foam and Unitrack to cork flawlessly. Dries overnight with no melting, distortion or strong odors. When it came to dismantle the layout, the foam broke long before the glue joint. Available at the big box home centers and chain hardware stores. As for filling gaps and leveling, I used Red Devil Onetime lightweight spackle. Adhered well to foam and cork, quick dry and easy to sand. I’m not a shill for these folks, and I don’t know about the other products discussed, but these worked well for me and are readily available in most places in the US and Canada.
The continuation of the original thread would provide additional insight to potential responders and might result in a faster, better solution. I’m curious why you would need 48 tubes of caulk…how about a photo to show us what and where you’re trying to fix?
If the adjoining pieces of foam are close to level, I’ve actually used either a sanding block or my random orbital sander to fine tune the joints with good success. Since the sander has a dust bag built in, there was minimal mess to clean up.
You have made the common most mistake when using caulking. You need to use the right stuff Latex "adhesive" caulking the key word here is adhesive. Your not trying to seal something your trying to glue two pieces I would be willing to bet that if you read the label of that stuff you used it says some where non hardening. You oculd leave that stuff there virtually for a hundred years and the two pieces would never bond.
The caulk of choice is DAP 3.0 latex ADHESIVE caulk it has a 3 minute sure time and is the ONLY stuff to use for adhering foam or gluing down track and roadbed. There are different adhesives used by contractors to bond foam to masonry or wood etc. take a few minutes and view the isle at your local home center and you’ll see how many different types there are. You made the common mistake many have made in that you looked for something cheaper I’m sure. Granted the DAP stuff is not cheap almost $6.00/tube around here but it cost more for a reason it works.
As far as removing the silicone caulking there is a trick I use that will definitely hep you in removing silicone caulking of any kind but i must preface this by saying i have no idea what it will do to foam if anything as I have never had to use it on foam. Good old Ammonia is the only thing I know of that cuts silicone. I had submitted this tip to MR got an email back but never heard anything more about it.I had used silicon adhesive caulk on a couple of bridge abutments and Chooch retaining walls and decided to change the scene and wanted to reuse them but removing them form the plywood sub structure more then likely I would have most certainly wound up breaking them if I tried to pry them off the wood with a putty knife or the like… I then remembered an auto mechanics trick of soaking the parts in Ammonia. So I poured a half gallon into a plastic shoe box and let the parts soak for a while and sure enough I took them out and they came apart relatively easy and without breaking them. I didn’t want to hog u