Just past the east end of the town of Dos Manos on my 1/24th scale railroad, there is a wiring junction set into the ground between two tracks. Last fall I poured a mortar foundation around the junction box:




For a long time I had wanted to put a building there, and finally decided that an old, concrete jailhouse would be just the ticket. It would be smaller, but similar in style and materials to the jails in Rhyolite, NV and Julian, CA. I could have built a form and cast the whole structure in real mortar, but I preferred to build it out of Sintra PVC board. I just had to come up with a way of texturing Sintra to look like cast concrete.

The Winter 2014 edition of the Modeler's Annual had a great article by Alexandre Duchamp on using artist's molding paste and other materials to model concrete and plaster surfaces. This inspired me to see if I could take it a step further, and replicate the look of cast concrete.

First I built the basic substructure out of 6mm thick Sintra PVC board:




Then I built a simple, flat form out of cedar stripwood I had on hand. I sprayed the form several times with Pam, a non-stick cooking spray. I gave it time to soak in between each coat.

I mixed some acrylic molding paste with a bit of Liquitex "ceramic stucco" acrylic texturing gel, plus a bit of concrete-colored latex house paint. This mixture was spread thin over the form, and allowed to dry. 




When it was thoroughly dry I peeled it off the form. Next I mixed some molding paste and latex paint, and spread a thick layer onto one side of the building. I applied the dried, textured sheet, starting at one end and carefully pressing it into the wet layer. The trick is to prevent trapping any air under the textured sheet. Then I let this dry for two days, leaving it in the sun as much as possible.




When I was sure it was dry, I trimmed off the excess material from around the edges of the building:



This method worked pretty well. It wasn't quite as flat as I wanted, so for the remaining walls I did things a bit different. In the end though, this initial approach was what worked best.

On the remaining walls, I left the dried layer of molding paste attached to the form when I pressed it into the paste on the side of the building:





Unfortunately I could not avoid trapping some air between the dried layer, and the wet paste. This caused wrinkles and depressions in the surface:




I filled in the bad spots with more of the molding paste mixture, and scraped it smooth with a flat edge. When it had dried, I sanded it a little as needed. This turned out ok:



I tried variations of this approach on the last two walls with similar results. 

The roof would not need imprints of a wooden form, so I just used a spatula to spread the molding paste/stucco/paint mixture onto the surface of the roof. It took a couple layers, letting it dry in between. Then I sanded it a little to smooth out any excessively rough spots.




There is a small window on one side of the building. Of course, it needs bars. So I built a frame of 6mm Sintra. Brass rods were glued into grooves cut into this frame:




This was then glued onto the interior of the wall:




A thin coat of the stucco/paint mixture was spread onto the edges of the window, and around the bars. When dry, excess material was scraped off the bars, and the rest was sanded smooth. The bars were chemically blackened, then painted. Finally, a fine brass screen was blackened and glued to the interior, to keep out insects:




The building was weathered by first mixing a slightly darker version of the "concrete" colored paint, and dabbing on random blotches with a rough sponge. Some extra dark blotches were added along the bottom edge of the walls. When that had dried, I went over everything with a very, very thin wash of "dirty gray" -- a mix of black and brown acrylic paints. The finishing touch was dry-brushing on a mix of "concrete" latex paint and white acrylic paint. Here's how it turned out:




The door was patterned after the riveted steel door of the Rhyolite jail, though not an exact replica. It was made from styrene strips glued to a block of 6mm Sintra PVC. I used .030" Tichy rivets set into drilled holes. Here's an in-progress shot:






Here's the door with a coat of primer. After shooting this photo I realized I had forgotten the hinges -- these were added later:




The door frame needed to be inset almost flush with the surface of the concrete. So I put the door in place and cut around the frame with an X-acto knife. Then I carefully scraped the textured molding paste off of the PVC substrate:




Naturally, I needed a padlock for the door, so I made one out of brass. I simply bent a thin brass rod into a U shape. Then I wrapped a strip of .001" thick shim brass around it, and soldered it in place. Later, this was cut off at the base and filed smooth:




Here's the finished front wall of the jail:




A close up of the padlock. The door was painted a rusty brown using craft acrylics. Then I used a rough sponge to dab on random blotches of a cake decorating gel. This was over-sprayed with a thin coat of black paint. When washed in water, the decorating gel comes off, giving a peeled paint effect. I finished it with some washes of various rust colored craft acrylics:




The sign was printed on self-adhesive vinyl and sprayed with Krylon UV resistant matte clear. I used craft acrylics to weather it, to look like rusty, enameled metal:




Here are some shots of the building temporarily in place on the layout. I still need to build up the scenery around the base of the building, then add shrubs and other details. I had intended to wait until this was done, but I was so excited about this that I couldn't wait:








Overall, I'm fairly pleased with how this turned out. The technique certainly has promise, though I'd still like to work out a way to get a flatter surface without any wrinkles or air bubbles. 


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