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Weather a brick structure

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Brick structures show their age in ways that are easy to reproduce on our plastic models. Paint washes and airbrushing can give brick buildings a sense of age that makes them look well used and authentic.
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Common in residential, commercial, and industrial districts alike, brick buildings are fixtures on model railroads of every era. And while buildings in the first two locations may appear well cared for, industrial structures ­often show their age. But what might ­reflect badly on a business looks great on our layouts, giving our structures a sense of realism and history.

Modelers over the years have used many techniques to weather their brick buildings, from drybrushing to airbrushing to paint washes to powders. I’ve used all of those methods, building up the weathering in layers depending on the material I’m working with and the effect I’m trying to achieve. In this case, I wanted a fairly heavily weathered industrial building, and was working with a plastic kit, so I used several paint-based methods.

I started with Walthers’ HO scale Water Street Freight Terminal kit – or, specifically, the two-story half of it. ­Walthers sells this part of the structure separately under the name “Brick Office Building.” I bought the freight terminal kit because I originally planned to use the single-story half, but I soon realized that with a few modifications, the taller part could be a credible small industry on its own. Also, its height and lack of roof overhangs provided better opportunities for weathering. The warehouse half became a project for another day. Here’s what I did with the brick office.
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Steve’s first step was to airbrush the entire building with Model Master Concrete acrylic paint. Though the upper part of the structure will be painted red later, this step provides an even base color on both the red kit parts and the white additions.
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Steve masked the foundation, steps, and loading dock with blue painter’s tape and sprayed the upper portion of the building with Model Master Oxide Red. The color may look unrealistically vivid now, but subsequent steps will tone it down.
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Steve flowed a wash made of one part Concrete paint, one part 70 percent isopropyl alcohol, and two parts water between the bricks to simulate mortar. Older buildings or those in the vicinity of steam locomotive exhaust might have darker mortar.
Step 1: Base colors
I could have assembled the structure as an office building. But using half of the loading dock from the freight house kit and replacing a pair of windows with a roll-up loading door made it into a more interesting rail-served industry. I also had to scratchbuild the lower half of the back wall where the warehouse was originally supposed to attach. So while I was doing that, I included a truck-loading door.

These modifications left me with walls that were part red plastic and part white, so I airbrushed the structure using Testor’s Model Master Concrete acrylic paint. (For airbrushing, I thin Model Master paints about 50/50 with water and isopropyl alcohol.) Only the foundation would remain this color, but I sprayed it on the whole building as a primer coat. This ensured that the next coat would have an even base so my changes would not stand out.

I let the Concrete paint dry overnight, then masked the foundation, stairs, and loading dock with blue painter’s tape. I next painted the top half of the building with Model Master Oxide Red. This is a fairly vivid color, usually seen only on decorative glazed brick, but I knew that subsequent steps would tone it down.

After removing the tape, I used a fine brush to touch up the Concrete paint on the foundation where the Oxide Red had seeped under the tape. I also hand-painted the building details, like the roof caps and windowsills, with the same color. This gave the building a unified look.

At this time, I also spray-painted the window and door castings with Scalecoat II Coach Olive, a fairly generic industrial color, while they were still on the sprue. I installed the window glazing and set the doors and windows aside for installation at the end of construction.
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Steve flowed a wash made of one part Concrete paint, one part 70 percent isopropyl alcohol, and two parts water between the bricks to simulate mortar. Older buildings or those in the vicinity of steam locomotive exhaust might have darker mortar.
Step 2: Mortar
Some modelers like to brush powdered pigments into their brick work to represent mortar. I’d do that with a cast plaster or embossed matboard kit, but when I’m working with a non-porous material like resin or styrene, I prefer paint wash. I make my mortar wash from one part paint, one part 70 percent isopropyl alcohol, and two parts water.

Though your first instinct may be to reach for the Reefer White paint to mix your mortar, think again. Though it may look good close up, from a distance the effect may be a structure that looks pink. Even those buildings made with white mortar wouldn’t stay that way for long. Use a light to medium neutral color, or for a particularly old or poorly kept building, black. I used Concrete for this building to match the foundation.

The alcohol in the mortar wash cuts the surface tension and lets it flow freely. It’s important to keep the brick surface level when applying the wash and while it’s drying, to avoid puddling. Dip a soft paintbrush in the wash, touch it to the brick, and let it spread through the joints on its own.

Resist the urge to brush the wash around, as that will encourage it to dry on the surface of the brick, rather than in the crevices. If you find you’ve applied too much, tilt the model slightly and soak up the excess with a clean paintbrush or the corner of a paper towel. Don’t wipe. Also keep in mind that the mortar will dry darker than it looks when it’s being applied.
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Flowing random spots of different colored mortar wash in between the bricks simulates repointing, the process of replacing crumbling mortar on existing brickwork.
Step 3: Repointing
Mortar can deteriorate over time, especially older limestone-based mixes and those exposed to corrosive coal smoke. The process of scraping out crumbling mortar and troweling in new is called repointing or tuck pointing. Though a masonry crew may try to match the color of existing mortar, it’s not always a concern. The result, seen in many older brick buildings, is a patchwork of multiple mortar colors. Stains that may wash off the surface of glazed brick but stick to more porous mortar can also cause this.

After my mortar dried, I repointed random areas by dabbing small amounts of washes made from a few drops of Reefer Gray or Engine Black paint in a quarter teaspoon of isopropyl alcohol (about 1.25 ml). The alcohol’s low
surface tension makes the wash spread through the cracks without discoloring the brick surface.

I installed the metal and wood loading doors at this point, drybrushing on streaks of Earth and Rust to simulate scrapes from repeated use.
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After the mortar and pointing, Steve unified the colors with a light spray of Grimy Black paint. He concentrated it bear the top and on the loading dock side. Next, he sprayed Earth paint below the windows and along the foundation.
Step 4: Overcoating
Structures in the steam era quickly acquired a coat of grimy soot from industrial smokestacks and locomotive exhaust. I simulated this on my structure with a light spray of thinned Grimy Black, which also served to tone down and unify the coloring. I diluted one part of Model Master acrylic paint with one part of 70 percent isopropyl alcohol and two parts water, then airbrushed it in light layers. I emphasized the top of the building, especially on the track side, and the vertical pilasters. I also darkened the concrete foundations, which would show more dirt than the darker brick.

Rain serves to wash dust and soot down the sides of a building. Interruptions in the walls, like windows, awnings, or overhangs, divert this flow, making vertical streaks. I air-brushed Earth paint, thinned with water and alcohol as with the Grimy Black, to simulate accumulated dust and detritus from deteriorating concrete windowsills. I also sprayed Earth along the base of the foundation, where more dust would be kicked up by passing traffic.
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By repainting a section of brick and concrete with unweathered colors and a fresh mortar wash, Steve simulated a repair. He also added a metal guard with visibility stripes.
Step 5: Simulating a repair
Even small changes to brick buildings are usually obvious. New bricks and mortar stand out against older masonry where a window has been plugged, a door added, or a damaged wall repaired. To give my structure an interesting narrative, I modeled a repair to the corner nearest the truck loading door.

I used the back of a hobby knife to scratch a crack into the concrete foundation, then painted the area on one side of the crack with fresh, unweathered Concrete. I also hand-painted several individual bricks above this area with Oxide Red and flowed in fresh mortar wash. Finally, I protected the corner from future truck damage with an angle iron (actually .080" styrene L-angle) hand-painted with Signal Yellow and Engine Black visibility stripes.

Next, I gave the loading dock the look of aged wood with washes of Grimy Black and Roof Brown, lightly sanding between colors. Finally, I installed the door and window castings and window glazing.

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