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I'm gonna show you how easy it is to carve convincing stone block tunnel portals, retaining
walls, and other structures out of foam insulation. A 10 dollar 4 x 8 sheet will make a lot!
The tools you will need are an old soldering iron, sandpaper, knife, a guide board to make
the blocks, mine is ¾" wide and thick enough for my soldering iron. A ¾" square stick,
a square, and a wire brush. And not pictured is a tape measure.
Using a 14" square piece of blue foam, mark the center, and measure out 3 and a half inches.
Draw vertical lines, and a peak at 9" Transfer the center mark to the peak and using
the ¾" square block, straddle the center and mark each side. This will be the bottom
of the keystone. Now using the square block AGAIN, line it
up against the side of the keystone mark and the arch line. Draw the other two sides, move
to the next position against the arch so that the lines will be radiating out from the arch
and continue drawing around the blocks. You don't have to be too precise at this point.
You will use these lines as guides and can alter them slightly while carving.
Now take the square block, placing it a block higher, this time lining the edge to center
and mark the other side. Repeat this on the other side of center. Now you can draw in
the sides of the keystone, but save the top till later. So this is the rough outline.
This is to show you how the guide board works with the soldering iron. The tip will penetrate
the foam by around ¼" . and The shaft will ride the board to give a steady depth. Exaggerate
the depth at this point because you will wear down the blocks later.
This is how to run the horizontal courses. Line the board up at the bottom and using
the board as a guide, melt a line across the foam. Then move the board up one course by
lining it up with the previous line, and melt the next line. Lather rinse and repeat until
you have laid all the courses. Once all the courses are done, turn the foam
90 degrees and start carving the vertical lines for the blocks. Line the guide board
up with the end and melt every other course, move the guide board lining it up with the
last set of vertical lines, and then alternate, skipping every other course. Continue in the
alternating pattern and you'll start to see the blocks.
This is how the tunnel portal looks after carving the blocks.
At this point, cut out the portal using the knife. You won't get nice edges, but we'll
fix that later. Continue the mortar lines around the edges
inside the portal, do the same to the the top and sides. I even continue the mortar
lines around the back slightly.
Now that all the mortar lines are melted in, I turn to the wire brush. I use one meant
for a drill because I have fingertip control, but a regular wire brush would work. Start
with the edges and square them up to the pattern, but round off the sharp corners.
When it comes to the block face, vary the depth and pressure at various spots to give
more 3D to the blocks. When wirebrushing the portal, I will undercut the blocks next the
arch and the top so that the arch and top stands out more. Don't be afraid to get too
aggressive, just go with the grain across
the blocks and dig in more or less here and there.
After a few evenings of work, you'll have enough tunnel portals and retaining walls
for your whole layout. Now paint them with a light color latex house
paint. this color was left-over from our house. It can be interior paint since it will be
sealed later. You can get these sample paints from Lowes for a couple bucks in any color.
It is important to get a good base coat, since if there are pinholes, the spray sealer will
attack the foam. Once the base coat is thoroughly dry I mix a brown latex paint with 10 parts
water to make it thin and runny. I Slather it on top of the base coat. if it's too thick,
I hit it with a water sprayer in spots. Stand it up and let it run off.
Once the brown is dry, I take a black latex thinned with about 10 part water and slather
that on. This time, I stand it upside down to dry.
Now that everything is dry, spray it with a krylon matte or satin finish sealer to protect
it from UV and start to set them on your layout. 7 new tunnels in a week. And some retaining
walls. Thanks for watching. I hope I explained the
steps clearly. You can turn these out in no time.