Over Foam For Mountains

[Anonymous]

I have a different take on the whole foam construction thing.

I don't use foam board products, aside from 1/2" foamcore for roadbed as a replacement for homasote or plywood. I use cardboard webbing and a hot glue gun to stitch together the basic hill forms where needed, then begin building up a mountain using expanding foam sealant, sold at hardware stores. Laying down a 1/2" bead expands out to become a lumpy 2" glob, so the ground literally grows before your eyes, and the benefit is that it has a randomness that boards lack. Once it has cured, I go back and use a big sharp kitchen knife to carve away the parts that grew too much, or where I would prefer a more uniform slope, and this way I can get very gradual shallow slopes that undulate rather than the absolutely flat sedimentary layers your get from board products. It's sculpture, but it's amazingly easy to do.

I cover this with my own home-brewed papier-mache mixture, although any non-brittle finsh coat can work. It works into the cracks and voids of the foam insulation and stays affixed by mere mechanical friction, as there is no actual bond, but the result is a sort of "softscape". It is lightweight and rigid, but with a lot of flex; I perfected the technique when working on a protable layout. My particular mixture is to start with Cellu-Clay brand papier-mache, which I prefer for its fine "grain", add in varying amounts of joint compound (for smoothness & carving detail), natural clay soils from the back yard (for color and for gritty texture), acrylic paints or india ink or tempera paints or any other water-soluble coloring (for color... make it darker than you think it should be, because when dry it will be much lighter), and even scoopable kitty litter (for rough textures or cliff faces). If you use the kitty litter, make sure that you get a brand that only has natural-color stones since many brands have blue or green scented crystals in them. Also, make sure you don't have a cat that is going to become confused by the smell and start scratching your foliage free in an effort to cover up its own unwelcome modelling contribution!

Trowel this mixture on using a plastic spoon (plastic because it is disposable); you load up the spoon and then dump out as much as you need where you need it, smoothing it with the bottom side of the spoon or carving it with the edge. With practice, you'll find that you can carve remarkable-looking cliff faces with ease, by adjusting the mixture for color and textural qualities, and all your rock-carving will be automatically integrated with your smooth slopes. While wet, you can sprinkle on extra dirt or crushed stone products to make it look like the kind of dirt you want (as opposed to mixing this expensive stuff into the plaster and losing most of it where it cannot be seen). Don't apply any green stuff yet; the goal is to create a hillside that looks like real dirt and rocks first, then add foliage later. This way, wherever you miss with the ground foam won't look unfinished, just barren. The papier mache will hold a watered-down glue type of fixative well when you come back to add greenery, no need to add detergent to create "wet water". And as for trees, they can easily be poked through the thin plaster layer and into the foam, though you might prefer to use an ice pick to create the hole.

I use variations of this same plaster mixture to create ALL of my scenery, from grassy slopes to glacial erratic boulders to cliffs, even paved roads (mostly joint compound). It flexes so it won't chip, and even if it does, what's exposed is already dirt-colored and dirt-textured. Give it a try!

[Anonymous]

i've just about reached the same stage....as Andy suggests, the shape achieved so far with power file,knife,wire brush looks pretty good and i may just paint over the foam...however if i need to plaster over the foam,is it desirable/necessary to paint the foam first ? i have some rock castings that i'll use also and intend gluing these in place rather than trying to set them in plaster. grateful for some views here.
brian a.

[Anonymous]

WE HAVE COVERED BOTH OF OUR MOUNTAINS, WITH TWO COATS OF BROWN PAINT,& THAT SHOULD GET RID OF THE PINK COLOR & YOU CAN ALSO USE THAT AS A BLEND FOR GROUND COLOR & DONT WORRY ABOUT MISTAKES, THEY SOMETIME LOOK BETTER>>>>>>>>>>>>>>.HUB

[Sperandeo]

Hello "pondman,"

It's an often overlooked option, but if you shape the foam to the contours you want you don't really need anything to cover it except thick latex paint and whatever ground texture or foliage you want to use. You might want a little spackle or putty as filler here and there, but mostly you can just apply your corors and textures right over the foam.

One of the first foam-scenery layouts I ever saw was Gordon Odegard's N scale Clinchfield project railroad, and it was built that way. gordy used a few plaster castings fro rock outcroppings, but that was the only plaster in the layout.

There's nothing wrong with putting plaster over foam if that's what you like, but I think that more people would choose to omit it if they realized that it isn't necesssary.

So long,

Andy

Andy Sperandeo
MODEL RAILROADER Magazine

[Anonymous]

I use Durham's Rock Hard Water Putty, mixed a little thin and with a little bit of water-based paint mixed in to give it the desired base color.

[pondman]

What is the best to use over pink foam board to cover it.Plaster of Paris or with a cloth in it too