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Modeling Mine and Mill Structures by Joe Crea

January 25, 2006

Many of the mines and mills in Colorado, especially in the
Black Hawk/Central City area, were constructed from stone
rubble. This kind of stone, which is not cut to geometric
shapes or laid in even courses, is one of the more
difficult materials to model well. In my opinion, carved
plaster renditions only look presentable in HO or smaller
scales. In “O” Scale and larger, such as the ½” scale in
which I model, I have struggled to develop another
technique which more accurately represents these rustic
stone walls that have so much character. For many years I
carved, cast and painted stone rubble walls, but was always
disappointed with the results. Even if I succeeded in
carving a wall that looked good, I was less than pleased
with the painted colors I applied.

So, I developed a technique which uses real stone. Because
the stone is real, it doesn’t need to be painted, and the
shapes and textures always look like, well, real stone. If
you want to give this technique a try, read on.

You will be building up each wall of your structure
separately and each wall is constructed with the finished
face down. Begin by drawing the wall you intend to model.
This doesn’t have to be publication quality - just an
overall outline with window and door openings, all drawn to
the scale of your model, will do. Tape this drawing down to
a piece of exterior grade plywood. Cut and fit stripwood
around the perimeter of the wall, using wood the thickness
you want the finished wall to be. Tack these wood strips in
place, leaving the tacks partially exposed for easy removal
later. I use blocks of foam, cut to size, for the window
and door openings. Tack them into place on the drawing.

Now the fun begins. Distribute small stones inside the
stripwood perimeter. You can just simply pour them into
place, one stone thick. I have found that for best results
it is worth the extra time it takes to fit them into
position, on at a time, as close as possible to adjacent
stones, flat side down. O.K., so this part is a bit tedious
- but hang in there, it’ll be worth it.

When you have all the stones distributed over the wall
area, pour a thick mixture of plaster over them, at least
as thick as the stripwood. I use Hydrocal for this, but, I
suppose, any plaster will do. I mix it thick because I
don’t want the plaster seeping through the stones and
coming to the finished surface of the wall. The purpose of
the plaster is merely to bind all the stones together. You
can remove any excess plaster by using another piece of
stripwood as a “screed.” This will also give you a smooth
interior wall, as many of these stone structures were
plastered on the inside.

Once the plaster sets up completely, remove the stripwood
around the perimeter and the foam blocks at windows and
door openings. I mix up some beige tile grout and then
grout the stone wall from the finished side. You can wipe
off excess grout with a damp cloth. You should now have a
beautiful finished stone wall that requires no painting!
If you sized your foam blocks correctly, Grandt or Simpson
doors and windows will fit into the openings in the wall.
Add more tile grout to fill any small gaps.

Cast up the remaining walls for your stone building and
glue them together with white or carpenter’s glue. Fill any
gaps at wall joints with tile grout. Add a roof and you
should have a very accurate representation of the prototype
stone mines and mills built in Colorado. Of course, this
technique can also be used to construct stone retaining
walls or structure foundations. If you would like to see
some actual stone wall constructions, view them in “Mines
and Mills in the Colorado Rockies” and the “Gilpin Ghost”
videos.

Joe Crea