These Dreams Are Made of Foam

 In North American model railroading, stone culverts aren't really a thing. Not that they never existed, but they never became ubiquitous like in Europe where a strong stone masonry culture existed and where railways were built in the 19th century to very high standards that had more in common with the Roman Empire than a large continent that was racing toward the Pacific Coast.

For this reason, beautiful stoneworks are generally associated with the Eastern Coast, where railways were built first. Since only a few lines had enough money to warrant large masonry works, they were a little bit rare. And when our lines were upgraded or improved, steel and concrete had become the new efficient way to build strong infrastructure.

Typical ATSF stone culvert near Colorado Springs (credit: L.C. Clure)

But beyond these clichés, there lies an interesting fact: masonry was indeed used on infrastructures even on the West Coast back in the 1800s. When I studied Raton Pass last year, I was impressed by the beautiful double arch stone culverts erected in the valley. Two large ones still exist nearby Wootton Ranch and are a testament of the ATSF commitment to make this railway a real trunk line. Such examples, while not ubiquitous with the West, where not oddities in the landscape. It was natural for ATSF to use the local limestone excavated while building the roadbed as a cheap material to erect culverts and small bridges. Since then, I've found a few pictures of these structures and wanted to incorporate one into the layout.

Carving individual stones is slow but rewarding

I thought about using embossed stone pattern  plastic sheets, but then decided to try carving high density foam sheets like most military and wargaming modellers do. I had purchased 6mm sheets from AK a few month ago for a concrete culvert on the Monk Subdivision. It was time to experiment.

I added capping stones on top of the walls

Cutting the foam to shape was quite easy with a cutter. This high density foam isn't springy like insulation foam (pink or blue), thus holds its shape much better. Right of the bat, carving was easy as it can be and I progressed "fast". Or should I say, it took 2 days! I would start by scribing the stone pattern with an Xacto blade at a depth of 0.5-1mm then opened it to shape the joint with a small styrene wedge I carved in a scrap of plastic. Nothing fancy. I made different ones to fit various geometry. When most mortar lines were done, I would come back with my little tool and shape the stones, giving then rounded corners and imperfections to get a more natural look. This was quite a tedious but satisfying work.

When all the flat parts were carved, I rolled an aluminium foil ball all over the surface to give it an irregular texture replicating roughly carved stone. This is an old trick and it certainly is the single most important step to make the result shine.

The vault is made of a kerfed foam sheet

I went all the way and also carved the barrel vaults. When the sheet was finished carving, I kerfed the backside following the same spacing than the stone rows. This would make the sheet flexible to get the correct radius. Tediously, each vault was glued with canopy glue, making sure the alignment was perfect. It worked better than anticipated and when it was completely assembled, I brushed a layer of white glue on top of the vault to fill the kerfs. This step ensured the vaults would keep their shape and wouldn't deform.

From inside, the vault looks like the real thing

Gluing is done step by step to insure proper alignment

One done, both vaults are great to look at...

The culvert was brushed with two coats of acrylic primer to sealed the foam. Then, I added a coat of diluted tan paint over the stones to get that Southwest color. This was followed with a wash of black India ink and isopropanol to make the details pop. Several drybrushing techniques were used to make the stone look more tridimensional, but the mortal lines were too deep and needed mortar.

Primer helps to spot things to correct

The initial color was tan to mesh with local limestone

Adding the India ink wash really made the stone realistic

I started by sealing the paint work with a thick gloss coat. My though was that it would make the mortar less likely to the stone surface while remaining into the cracks. I elected to use white tile grout to fill the gaps. I smeared it in the joints with an old brush. Then, I cleaned the stones by spraying water on the surface with an old spray bottle. The spray was strong enough to push away the mortar, and a wet towel was enough to remove the excess.

The tile grout is smeared into every nooks and crannies

I really liked the mortared joints, but the overall effect made it far too clean and bright. It had to be toned down with a very light India ink wash. Unfortunately, it made the stone loose its warm beige tint and all the mortar got too dark. My mistake!

Most of the grouting is completed except the wing wall

To fix it, I drybrushed the stone with different shades of tan to bring back their color. Then, I reapplied mortar in a few select areas. I made sure to clean it well and using a large brush, I clean the surface by wiping it down in a vertical motion. That way, any grout traces on the stone would look like lime leaching out of joints. That really improved the realism. A few spot washes and shadows were done using dry pigments to replicate places where dirt accumulate. I decided to not overdo the effect as the culvert isn't located in a very rainy area.

Stone colors are rectified with washes, filters and drybrushing

Overall, I really liked the process. The carving was fun and I can see a lot of potential in that method. The painting was challenging because I created my recipe on the fly and should have done certain steps in a different order. I think it will be a very nice addition on the layout and a future railfanning spot. For this reason, I elected to make the foreground deeped in that area to get better photographic potential.

The weathered culvert now in place on the layout