Step 5: Paint

After I was satisfied with the way the rock faces look, I applied layer of light grey latex paint. The foam soaked up the paint so it took several coats before it looked right. After the first coat was dry, I installed the mountain over the fireplace to ensure the train would make it through the tunnel.

The first coat of paint helped to highlight areas that needed work. I used an additional can of spray foam to fill in holes and remake areas that didn't look quite right. After the foam dried, I used the pull saw to trim off the rounded areas.

Using standard acrylic paints (from Hobby Lobby), I mixed up some dark grey and brown colors to feed through my airbrush. The first couple of passes didn't look too good -- the mountain looked as if it had a bad camouflage pattern. It took several coats before it started to look like actual rock.

One technique that I found useful was to "force" light and shadow. That is, I applied a lighter color to the rock faces that were more horizontal and a darker color in the crevices and vertical slopes.

Many model railroad websites recommended watering down the acrylic paint and then applying with a spray bottle. Unfortunately, that technique didn't work well with this type of foam as it was not as dense as hobby foam.
Are you sure that the recommendation for thinned acrylic paint was for foam mountains? Or was it for foam mountains covered with a layer of plaster. For example, using plaster gauze used for casts as in a broken bone? Or plaster coated paper? Or a coating of plaster spread with a putty knife? Or even plaster cast in a rock mold?
Awesome Instructable! These techniques are simple,effective and usable on many unrelateds. My only "criticism" (way to strong a word, as I really think it came out EXCELLENT) is there is no portal. Typically a tunnel has a concrete or stone block structure at the entrance and exit.
Thanks for the tip -- I suppose I could carve a portal out of wood or perhaps form it with Super Sculpy.
amazing job love the whole track did you know you could add a bit of realism to train by weathering
Thanks for the recommendation!

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Bio: Mad scientist, woodworker, creative evil, artist, tinkerer, father of five creative hooligans.
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