Thread: Hardening foam without losing detail?

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So here's my debacle...



I've been carving/sanding rocks for a project I'll be getting into rather soon, and have realized that I need to hard coat the "stones" to prevent/minimize any damage. Well, I'm having a brain fart, & can't seem to think of anything that will retain the level of detail I've put into them. As you can see, I'm off to a good start on the project and only thought of this just now. :/ Any ideas anyone?

dunno if this'll work or not but I once made a tombstone out of cheap white styrofoam and used cheesecloth and glue to make a coating for it... after several layers it is pretty tough and also retains a stone look to it. You get wrinkles and bumps and depth to it...

might work for you?!

Ten years ago I painted several of my foam things with outdoor paint and alot of sand mixed in. It has held up great all this time and gave them a hard coating.

*Slaps self in forehead* Duh, now why didn't I think of that? I've been using sand/glue & sand/paint with my carpet moss technique. Perfect! Thanks for the replies guys.

They look great so far! What will the rocks be used for?

If you'll remember, I said not long ago that I was about to commence work on my columns... Lol! Well, I started Windy weather prevented me from working on my obelisk for a couple of days sooooo...

Oh, and the hotwire table has been a godsend for this!

you can use a heat gun to melt the surface a little before painting that will also harden the surface

Smooth-On Smooth Cast Urethane Plastic comes to mind. Either 320, 321, or 322 series (320 has a working time of <3 minutes, 321 has a working time of <7 minutes, and 322 has a working time of 15-20 minutes.) Works well over foam (I used it over Great Foam and it doesn't melt it, etc.) I used it on my Alien eggs a couple of years ago, I got the 320 though, so I had to work quickly before it turned rock hard. It's a part A + part B type 1:1 mix. It's paintable too.
http://www.smooth-on.com/Urethane-Pl...210/index.html

Those are pretty sweet. I too am needing to sculpt some rocks. I don't know jack-shizzo about this foam stuff though. Question for you Raven.... Can you somehow glue 2 or 3 sheets together to make a thicker rock if you need? What type of glue would you use?

@ Caretaker & BWarriner: Thanks for the tips guys. The Smooth-On looks particularly handy, I'll order a trial size to give a look see. Because I can see this project taking a few gallons before it's complete.

Originally Posted by GhostTown

Those are pretty sweet. I too am needing to sculpt some rocks. I don't know jack-shizzo about this foam stuff though. Question for you Raven.... Can you somehow glue 2 or 3 sheets together to make a thicker rock if you need? What type of glue would you use?

Thanks! They're pretty simple GT. A little counter-intuitive if you've ever spent any time molding &/or finishing car body parts. In that bearing down & digging out the foam is exactly what you want to do while sanding them. While the exact opposite is what I'd normally be doing w/ sanding block in hand.


The adhesive I usually use is: Locktite PL300 Foamboard Adhesive, and you certainly can adhere more sheets together. You just want to remember to make sure the joints between the layers are well sealed (exterior grade latex paint is perfect for this). Because water penetration will soften, and eventually kill, the bond of the glue. You can get the foamboard adhesive at any local Lowes or Home Despot for +/- $3.50/tube in the paint section.


Once I build the frames (everything's already cut aside from the crown molding miter cuts, I just need to finish the obelisk revamp to make room to work). I'll be doing a mock up with the stones prior too gluing them in place. I've already tossed the idea around about doubling the stone thickness to give greater depth, and I'll make the descision then. One things for sure, the hotwire sure makes adding on a simple affair!