Adding the Unimin Mine (Nephton, Ontario) - Part 1

Geology 101 vs Model Railroading

I needed to take a break from the efforts of wiring, track work, etc on the paper mill modules before I tackled wiring the last island of the layout, so I decided to take a few days off and begin building my background for the Unimin mine area.  Unimin does open pit mining at its Blue Mountain facility, and while trying to model the open pit is impossible, I opted to model just a small portion of the mine, in the area where the mine trucks would be coming up and out from the mine.  While the area I have for the mine is fairly small and compressed, I really just wanted to give a sense of the mining operation and show trucks coming to the processing buildings.  As of summer 2015, the Blue Mountain open pit mine has been mined down to the 8th bench level, and mine officials project that there is at least another 25 years of ore remaining.

Blue Mountain Mine - Unimin

Initial base layer at the end of the new Unimin island of the layout

Now as someone who has a degree in Geology, I wanted the mine walls to show a level of creditability and really capture a rock face like you would see in an open pit.  Fortunately I was able to get some photos of the Blue Mountain pit and use them as a general guide.  However, I knew that I would be restricted in what I could model by both the areal size and vertical depth of the mine.  So my mine had to bend the physical reality a huge amount and have the haul road coming from only two bench levels, and telling visitors that the mine actually extends out into the aisle way.

So the first step involved cutting and attaching the base to the existing foam board. While I started with a 2" thick layer, I opted to cut that in half in order to have a rough surface.  The roadway cut into a 2" block also seemed to be out of perspective, so out came the cross saw and I carefully cut it in half.  Once this was done and glued to the base, it was time to start cutting the back pieces of foam to shape, gluing them together and then gluing them to the mine floor.  I tried to keep the same hillside profile by tracing the largest piece onto the smaller piece and then free handing the contour approximately 1" below the traced line.

Adding 3-D relief/base to the rock wall

Now comes the fun part, getting all those rock castings that I have made to fit into the designated spots, giving the impression of a hillside which has been actively mined yet still follows the fractures and joint patterns of the local igneous rocks of the mine.  While you can use large commercial castings, I prefer to cast rocks using a combination of commercially available molds and home made castings followed by large amounts of breaking castings into small pieces as well as cutting castings into small rock junks.  One of the keys to success is having enough rock castings available to you, as invariably you will find that your running out of castings or need a coasting that you already used for a certain space.  While casting is a relatively slow process, I have found that setting a number of "wet" castings onto a cookie sheet and baking them in the oven for about 60-90 minutes will greatly speed up the process. A "wet" casting is one where the casting has gone through the initial setup and can be removed from the mold, however, is far to wet to accept hot glue to place it on the layout. Of course, if you're going to dry castings in an oven, best to lay the "wet" castings on a piece of aluminum foil rather than upset your spouse by placing them directly onto the cookie sheet.

Fitting them against the hillside is done by the trial and error method.

Rock castings applied with hot glue

Before I actually glue them in place, I test fit them and then lay them aside until enough of the hillside is ready for gluing. Once the pieces are in place, you'll notice that you may have large gaps or cracks present.  The cracks may or may not require attention, as remember that rocks naturally have cracks or joints present as they have been altered by weathering and other processes.  Filling large gaps is easy enough, I simply mix some hydrocal into a fairly stiff mix (e.g. consistency like toothpaste) and force it into the spaces with my modeling or sculpting knife.  In many areas, I'll simply use my fingers to force the hydrocal into the gaps, making sure to get as little on the mold and obscure any details.  Since the molds are also made with hydrocal, there is no real difference in the coloring or how well the material will take the stain that we're going to use.  If you made your castings from plaster of paris, I'd suggest using the same materials too achieve that consistency.  One word of caution...try mixing small amounts of hydrocal, as the material sets fairly quickly (even when mixed with cold water) and working it into the gaps in a series of steps.  Too much materials mixed together will dry quickly, leaving you with firm hydrocal, which just has to be used as rock talus or thrown out.  For the area you see before you, I mixed 4 separate portions and applied them in small areas. After drying overnight, I'll come back with a knife and carve some additional fractures or alter the rock face to make it more blocky, giving the appearance of rock that has been blasted away or removed.

Upper rock face completed

Final result before adding the lower level and coloring the castings

The final step will be to add some additional Sculptamold to the top of the hillside, and add some tinting or coloring to the castings (to be covered in the next entry).