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""Great Stuff" insulating foam - good for mountains?" Topic

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886 hits since 15 Feb 2016
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Queen Catherine Inactive Member15 Feb 2016 1:29 p.m. PST

I got some of this stuff years ago to make mountains or sculpt hills. Never used it. Now I was about to give it a go and was reading the label, which reads like a warning of catastrophe, and I'm not certain it's a great idea.

Any advice or precautions?

As the ultimate goal is just to landscape rough spots on insulating foam mountains, can I use this at all or should I try something else?


Personal logo Jeff Ewing Supporting Member of TMP15 Feb 2016 1:37 p.m. PST

It is nearly impossible to remove once it's on, so wear gloves and put down newspaper. I think I would try using disposable plastic putty knives for sculpting it.

Mirosav15 Feb 2016 2:23 p.m. PST

Don't get it on your skin or clothes. Never tried using it for terrain, but you can cut it with a utility/X-acto knife after it is hardened. It is hard to shape when spraying.

Personal logo Sgt Slag Supporting Member of TMP15 Feb 2016 3:50 p.m. PST

There are two varieties: expanding, and non-expanding. The expanding variety is difficult to contain/control. The non-expanding is not so difficult, for obvious reasons. Some folks have had success using it, but an Internet search would be your best option. Cheers!

14Bore15 Feb 2016 4:57 p.m. PST

I use it at work, adding to extruded foam might be a use. Also it takes time to cure, it will skin over fast but the center will take maybe a full day.

tima113 Supporting Member of TMP15 Feb 2016 5:52 p.m. PST

For mountains or big rocks, use a crumpled newspaper core held together with tape, then spray the expanding foam in the general shape you want. Trick is to get the coating thick enough so you can carve it without penetrating to the core. After it cures for a day, carve away (I use a dollar store bread knife purchased for hobby use). I've used it to make a layered volcano quarter (fits in the corner of the board) and a "big rock" as a gag gift for a departing team lead.

Personal logo Narratio Supporting Member of TMP15 Feb 2016 8:18 p.m. PST

As tima113 says. I use sheets of insulation board cut for a basic shape and the expanding foam (usually Hilti Fire stop… it was left over on a construction job, honest) to smooth out contours or make improbable, imposing rock formations.

(I admit that once I did cover the top of a hard hat with some to express displeasure. It dries to a nice light brown colour…)

Most of the dire warnings on the side of the cans are for insurance purposes. Used in a ventilated location you've no problems. However, if you insist on using it in a small sealed room at the height of summer while smoking a cigarette then congratulations, you're up for a Darwin Award nomination.

John Treadaway23 Apr 2016 10:54 a.m. PST





These were all done a decade ago by me using spray foam on a chip board base with walls cut from block foam (the hard stuff: pink, I think).

The foam was the expanding kind and was very messy and stuck like you know what to a blanket. I carved it back into shape with an old electric carving knife.

Sadly is all went in a skip 6 months ago when I moved house.

It was built for the 1/25th LotR game we did.

John T

The Angry Piper Supporting Member of TMP15 Mar 2017 11:24 a.m. PST

Mel the Terrain Tutor did a Youtube video of this recently. Like most of his stuff, it's pretty thorough!

YouTube link

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