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To attach a plaster casting, be it from a rock mold or anything plaster or hydrocal, to foam (extruded foam) What is the best adhesive to use. I see some using "hot glue" from glue sticks. Others use some form of adhesive like "liquid nails". Or even making a patch of wet or fresh plaster, although that seems like a lot of extra work. What about the same type tube caulk that is used for putting down track?



Hot glue might melt the foam. I will most likely need to glue plaster rocks to my foam layout and will probably use latex caulk. I used caulk once before to glue foam to wooden benchwork and because of a move, had to pull it apart. Man, that caulk holds tight. It's cheap and paintable too.

NH Mike

CEO & Wheel Cleaner
Caulk will work and so will silicone sealer of any type. I use cheap clear silicone. For both I rough up the foam with some 60 grit sandpaper or randomly gouge it out with a hobby knife in the area that will be covered by the rock mold. The roughness will give the adhesive something to bite into rather than the smooth surface of the foam. If the back side of the rock casting is smooth a quick scuff with 60 grit paper promotes better adhesion.

Pretty much anything will work except for solvent based adhesives that will attack the foam. Water based adhesives like Woodland Scenics scenic cement or Elmers glue will work but can be softened and dissolve if they become very wet with water during finish scenery work.


I've used all of these methods depending on what I needed. It really depends on how quickly a set you need and whether those castings will lie horizontal and have their weight supported during the adhesive cure time.

Here is a sample - the rock formations are not hydrocal, but are made with Durham Hard Water Putty and weigh a fair amount. I used hot glue to set them from the back of the casting, and then used a modified method taught by Joe Fugate (his videos are downloadable and I highly recommend purchasing them!). I mix spackling and plaster of paris with a bit of powdered tempera paint to color the mix. This is spread with an old brush and shaped into the landform I need to blend the castings. While this is still wet, I lightly dust the material with fine ground dirt that I purchase from Scenery Express. I do like the results...


add some plaster-cloth over the foam, then glue down. The plaster-cloth will insulate the foam from the heat of the glue gun.


New Member
Use Aleene's glue, buy at Walmart or any craft store. The plaster rock casts from Western Scenics. The foam board is blue insulation board, the foam board at craft stores has too much texture.
Aleen's Turbo glue dries fast, slower dry glue is regular. Also use the same glue for foam track bed and my tracks, hold in place with push pins. While the plaster glue sets hold in place with small weights.

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