My mountain base is made from foam it is vertical where I will attach hydrocal rocks made from molds
My question is should I attach the rocks to the foam if so with what (chaulk,plaster,glue) or should I apply plaster cloth over the foam and attach them some how again with what. I want a permanent bond
There are so many options for the adhesive. The methods I use that have worked well are:
When placing wet/just poured molds directly to the foam, I bond with an additional buttering batch of colored plaster. Any oozing “glue” can be carved/ shaped shortly after peeling the mold (20-30min using Hydrocal-longer dry time for other plasters). Now the area between castings are fit with cut/trimmed dryed castings these can be applied with the same mix of the plaster bond or I will use ceramic tile adhesive. The colored plaster seems better, but don’t have the luxury of much time for positioning castings as the working time is rather short. Again, the advantage is the colored plaster ooze can be used to fit crumbs/ pieces or left to dry and shape.
An additional method is to just bond pre-made castings (pre colored) with liquid nail, acylic caulk, hot glue. These are used by many. I still like the placement of critical pieces dierctly on the foam first, as it gives you the ability to conform the casting to the irregular surface (concaved or convex). And use the tile adhesive most of the time for placing additional pieces in between of it is just a few random outcrops.
Hot glue seems to work good for placing those crumbs in an already laid up rock cut. Can use it as a caulking so to speak, add squirt and shape as it cools. (Use care not to be burning fingers). I have even found that drooling hot glue simulates water running down the rock face.
Caulk or any other adhesive of choice will bond the pieces also.
I wouldn’t bother trying to place plastercloth first, unless the situation required it for other reasons to se
Hot glue works wonders! I’ve used it on hydrocal castings and it’s great.
[#ditto] Yuppers…hot glue works great… It will hold for days, until you work some hydrocal or sculptamold around the rocks for blending, which then really holds them in place… It does not give great lateral strength, so if you are doing a lot of banging, moving, etc., they may fall off. This can be a mixed blessing if you have to move one of the castings. Just twist and off they pop!
Brian
I use drywall mud, applied to the back of the casting. Any that squeezes out can be used to blend the castings together. Just make sure you dampen the casting some first.
Nick
Silicone adhesive works well for hydrocal. It’s one of the few things that will bond hydrocal castings to styrene. It gives off ammonia fumes when it cures, though, so be sure your layout is well ventilated when you do this, or attach the hydrocal to the foam somewhere else (outside or in a garage) and then move the whole thing once it’s set.
Liquid Nails for projects, Some applied when partially set up, and some applied with the plaster buttering method, with the first two preferred for me.
Paul
Dayton and Mad River RR
Try using Acrylic calk or RTV to attach the rock castings. In some cases, liquid nails can eat the foam, and hot glue would melt it.