# How-to: building terrain with insulation foam and plaster of Paris



## tankist

while i did not invent any of the techniques i below, here is a short write up on how i approached construction of my layout.

the layout is build on 4x7 table. frame consists of three 2x4 beams lengthwise across 4 beams slot joined so to keep them one piece for added strength. glue and wood screws (pre-drilled) used to hold the frame together. 











sheet of chipboard is attached on the top of the frame. 2" thick pink insulation foam is glued to the chipboard creating the base surface. Mountains are comprised of layers of pink foam glued to the base layer. i didn't bother cutting monolith pieces and glued any insulation fragment i could find. rough shaping of the terrain was done with wide snap-off blade knife. small and flexible 9mm blade was used for finer detail. bits and pieces were glued in to add terrain (or to fix mishaps of to much removed ). in locations of future roadbed/track surface was smoothed with diamond tipped hacksaw blade uses in a file manner. the length and flexibility allows the blade to be curved around bands creating uniform slopes (shop vacum is strongly advised).
several coats of joint compound were used to smooth out the terrain and fill any dips and cracks.

layers, bits and pieces of insulation are visible here 











rock faces are made with plaster of Paris. prepared mix was cast into heavy duty crumbled aluminum foil (for better results WS rock molds can be used.) and attached to roughened bare foam sides . seams form overlapping castings were scraped and smoothed immediately before the plaster was totally cured.


experimented with armature made of wire hanger. not needed.











plaster of paris hardens VERY fast. couple first tries hardened before they could be pressed into foam.












Painted with white,textured gray, flat gray, black rattle spray cans over base of biege latex paint. still learning


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## Big Ed

looks nice tank, looks real.
I read something somewhere about adding some small dark shadows to make the rocks POP out. But you got to shadow it just right or else you can ruin the look.

When it comes to painting something like that I guess it helps to be part artist.

You made a 4x7 table? How come you just didn't make it a 4x8?


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## tankist

thank you, but i was hoping to achieve better results as far as rocks. for starters i should have used a dental pick and try to detail the faces more while the plaster was still not fully cured. it is not professional grade work and as such i was kind of reluctant writing a how-to about the subj... but perhaps someone will find it of use.

as far as paint, now i know that instead of base layer of latex i should have started with india ink wash. and then painting is a topic all by itself. now that i own airbrush, i will try to improve on my previous work.


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## Reckers

It looks great, tankist. Hey, have you ever considered using a spray solvent on your foam to disolve it? I've been wondering if something like acetone, lightly sprayed, would cause the outer surface to dissolve and run slightly, then set up again. I was going to test it myself this summer, but thought I'd rather risk your layout first.


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## tworail

I will be using this technique on my layout for sure. Nice write up.


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## tankist

I have no illusions, my looks OK (subjective) and might get somewhat better with touch paint touch-up + vegetation. below is how "great" should look like.
perhaps my next one will be closer to this.











melting the foam with corosives or hot knife is something i never considered. somehow breathing acetone fumes + whatever foam releases while loosing volume, does not sound like good idea to me


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## Reckers

I still like the flying-buttress effect of those arched bridges. There is something about the way they are so smooth and graceful that's almost surreal. They're almost like art-deco bridges.


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## Big Ed

Theres all different kind of rock cuts. If you don't like it can't you just add some to the top of what you all ready have?

I saw some rock cuts up in Mass today that reminded me of your rocks. It's where they cut through a mountain for the big road to go through. 

The only thing that yours were missing is the vertical lines that the drill made to place the explosive charges.


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## Reckers

big ed said:


> Theres all different kind of rock cuts. If you don't like it can't you just add some to the top of what you all ready have?
> 
> I saw some rock cuts up in Mass today that reminded me of your rocks. It's where they cut through a mountain for the big road to go through.
> 
> The only thing that yours were missing is the vertical lines that the drill made to place the explosive charges.


Tankist...I can get you some firecrackers, if you want to fix that.


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## redwine_p

do not use an acetone !! or the likes there of. it will eat your foam and never stop till you have a bunch of goo running everywhere like gasoline in a styrofoam cup. (first hand knowledge) . What i do is take and cut the foam with a hacksaw blade. makes pretty nice cuts and is inexpensive and can be bent to form different angles. when it is all done i then take a cigarette lighter or my trusty little mac tool torch and heat the edges of the foam ( can be done with a heat gun as well ). The foam draws up, seals,takes paint well, and looks like real rock faces when it is done. 

Just my 2 cents worth....


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## Reckers

Thanks, redwine. I knew acetone applied heavily would do that; I had wondered if, by using just a fine mist from an adjustable spray bottle, I could limit the 'melting' of the rock face; the idea was to have a more weathered appearance. Heat may be the answer. What I was trying (in my mind) to accomplish was a difference in texture between old, weathered rock, and the sharply defined edges of a new cut.


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