Rock molds

Loc-tite?  Liquid Nails?

Will liquid nails hold over a long-term i have never used liquid nails 

I would think so. I used actual rocks on my layout secured with liquid nails. They are still holding firm after many years. Good luck.

The items are porous, so yellow carpenters glue should work. Also add some two-part epoxy.

MELGAR

I usually attach rock molds directly to rigid foam so I use Loctite PL300 along with hot melt glue.  The hot melt glue gives you an almost instant bond while the PL300 makes sure it stays put.

I use Joint Paster Compound. I take a big gob of it spread it all over the back of the "rock" and let some come out the sides. This will fill in between your next rock. Been doing that for years on three layouts and never had any fall off. Even my 2x3 foot rock molds. I make hydrocal rock and let them dry completely so they are very lightweight. Don

Thanks guy's i have alot of ways to try now. scale rail I'm going to use your way when i get to my mountains

Similar to Don, I set them in sculptamold so that they can be blended in. You can also glue them on and then go back and blend in the edges after the fact too.

Plaster to wood should be pretty easy to bond as both are pretty porous. Wood glue or epoxy would do the job. I would think any construction adhesive (liquid nails) would also get the job done. If you want instant results, hot glue it. Whatever you go back with and blend everything together (plaster, joint compound, sculptamold, etc...) will serve to further bond it all together.

Lionel40, The layout here goes from a little over six ft. high to the floor. Its a three sided canyon. I bought really large molds from a guy in California.  Some of the "rocks" I would drop and let them shatter. That gave me many small pieces to fill in between the large rock walls.The second shot goes to the floor. Don

I also use "Blackwrap" on the mountains for a basic shape. Blackwrap is like black aluminum foil but much stronger and thicker. It's used to flag off stray light on movie and TV productions. When I like the shape I do a light layer of hydrocal soaked paper towels. When dry it's amazingly strong. Then it's time to add your molded rock. You can order Blackwrap here: https://www.filmtools.com

Filmtools is in Hollywood. Hope this helps guys. Don

c

Used this stuff all the time in my stage lighting business. Wouldn't leave home without it. In a pinch, it can transform a par-can into something it's not. Being thrifty, we would reuse to the point where it became too wrinkled. With that in mind, it could be effective in creating nicely textured tunnel walls...

I have three rock molds, should be available from one of the scenery supply companies.  Click on underlined phrase to link.   As mentioned, construction adhesive works well, for attachment to sub-structure.  Fill-in-the-cracks materials, Plaster-of-Paris, and Hydrocal plaster (5 gallon bucket).  Safety meeting of the day.  Material can be not so friendly. Dispose of waste, in the solid waste garbage, down the drain, not a good idea.  

Jon, I have used Blackwrap for two tunnels, just crunch it up, shape it the way you want, add a little detail paint and you have the inside of your tunnel. Don