Weathering Railroad Models – Hopper Car Interiors

Recently weathered HO scale hopper cars, and one gondola.

About a month ago I shared this lead image on Facebook and with a few friends. There were several compliments and a recurring question, “How did you do that?” Here’s a walkthrough of the basic steps I used on these hopper car interiors. Click on any image here to review a larger version.

I find inspiration in prototype images for many model projects, including weathering. Color images of the steam locomotive era can be found through the American Memory pages at the Library of Congress web site. Photographer Jack Delano captured many railroad scenes in the 1940s using color film. One of his images offers us a hint at the interior of hopper cars. Shorpy has this available. Make sure you click on the View Full Size link.

As weathering on the prototype freight cars did not happen all at once, we should consider several steps to replicate the many effects of Mother Nature. I look at weathering as layers of material and I frequently use a mix of media as the layers are applied.

HO scale hopper models before weathering.

The first layer is the original body color. In most cases, this color has been applied to our model at the factory.

Hopper models after initial application of earth brown paint.

The next layer is a grimy, dirty brown shade because coal is very dirty stuff. I use a rattle can of Krylon Camouflage Earth Brown to establish this dirty interior base. A mask cut from a cereal box is used to keep the spray directed onto the interior surfaces. Compare the image above with the image of the plain model.

Basic paint, thinner, and cheap brushes for the rust layer of weathering.

The rust layer comes next with a custom paint mix for each batch of cars to create a color shade variance. Craft paints are used, starting with several drops of terra cotta applied to a cheap palette, such as the yogurt container lid. Three drops of oxide brown are added and mixed together with a Q-Tip. Yellow or red can be added to achieve different shades of rust. A squirt of cheap window cleaner thins the mix to a chowder-like consistency. A runny mix is too thin. Use a cheap brush with short bristles to work the rust color into the hopper crevices. Start in the bottom and work your way up the slopes and sides.

Hopper interior after rust paint has been worked into corners and surfaces.

Refer to the prototype image and note how the rust seems to end where you would see the top of a load. Use the paint sparingly and scrub it into place, pulling it up interior walls and slope sheets. If there is excess in the bottom, use it on another hopper rather than using paint from the palette. Don’t think of coating the surface with color, but rather think like you are pulling color across it.

Allow plenty of time for the paint to dry between each step. If you live in a humid area, wait a day or two before proceeding to the next step.

Basic paint, thinner, and cheap brushes for the grey layer of weathering.
Basic paint, thinner, and cheap brushes for the grey layer of weathering.

Once the rust color has set, I turn to another scrub using a slightly thinned acrylic grey. This scrub tempers the boldness of the rust and can simulate bare, worn metal areas. Just wet the tip of your cheap short bristled brush and dab a couple of spots onto a slope sheet. Scrub these spots in the direction of the slope and pull the paint around. Add a little paint to the brush and work on another area in the same manner. Work on the interior sides and scrub all the way to the top.

Hopper car interior after grey paint has been applied.

The car interior is looking pretty good now, but it’s missing some grit. I use a soot color of weathering powder from Bragdon Enterprises. Just a little material on the ends of your favorite cheap brush goes a long way. Focus on the slope sheets and some of the angled surfaces in the hopper. Empty any excess onto a sheet of paper, or into another hopper car and work it around. Here’s what the interiors can look like after these weathering steps.

The final appearance of the hopper car interiors.

Give this a try to add color and texture to your empty hoppers. Many gondolas would have a similar look, but seek out prototype images to guide your work. One pass of one shade of paint doesn’t quite look right as the prototype was not weathered in one pass. Once you get the hang of it, work in batches of two, three, or four cars at a time. I’ll cover exterior weathering ideas in an upcoming post.

I hope you found these steps helpful. Grab a model or two, some supplies, and dive right in! Your questions and comments can be posted below. All comments are reviewed and approved before they appear.

11 thoughts on “Weathering Railroad Models – Hopper Car Interiors”

  1. Great ideas, Eric, especially the suggestion to look to prototypes for ideas on patterns of weathering. I have spent a few hours looking down into coal hoppers and been surprised how hoppers with nearly identical exteriors can look so different inside. Coal varies a lot, so when wet some, presumably high sulfur, coal generate more weathering-triggering acid than others. Some of the weathering edges are so abrupt that it looks like a single load caused a lion’s share of rust and corrosion.

    I also have seen some deposits in empty hoppers that I would not want to model, often left with a soiled abandoned railroad red hankerchief! It appears a empty coal hopper is a convenient private place in a railyard.

    1. Thanks for your thoughts and perspective, Steve! One element I did not cover here was how the prototype has changed over the decades. You were looking at hopper cars that were built using a steel that has more of an anti-corrosive quality, or possibly cars that were built with aluminum components. Coatings have also changed since the end of steam, so there may be some differences in what rust does today compared to the 1940s and 50s. I focus most of my modeling efforts on the mid-1920s, but there are no color images of that era so I’m extrapolating the details seen in the post-war photos for use in detailing models representative of an earlier era.

      And I don’t think I’ll try modeling those, umm…..”other” kind of deposits you mentioned…. – Eric

  2. Hi Eric,
    Fantastic results! I just happen to have all components on hand now and will test my hand at this in the very near future.

    Why use the window cleaner instead of distilled water?

    It’s finally warming up a little

    John Albaneze
    Streetsboro, OH

    1. John, it was a simple matter of having the window cleaner on hand in an easy to use spray bottle. I do need to pick up some distilled water soon as I get the airbrushes ready for the new paint booth. – Eric

  3. Eric,

    A great, timely and extremely helpful post! I do have one query: many railroads did not paint their interiors; what would you suggest for an unpainted “sheet metal” color for a base?
    Thank you

    1. Hey Brad! I’m glad you enjoyed the read. While some railroads do not paint the hopper car interiors, I think this is an issue of era. I am focused on the steam era and the documentation on railroads not painting hopper car interiors during the 30s, 40s, and 50s has not come my way. As steel companies developed more non-corrosive additives, I suspect many railroads did not paint the hopper interiors. There would still be rust as wet coal can leave behind an acidic residue that will attack steel.

      In the weathering processes outlined on the blog post, I scrubbed a grey acrylic layer onto the rust to convey some bare metal and to tone down the brightness of the rust. I also believe the bare metal effect is not as common as we think, at least not in large expanses of exposed bare metal in hopper interiors. There should be some streaks and divots exposed, but these areas would also collect remaining fine coal and dirt, and they would rust pretty quickly. A modeler can always drybrush more light grey to simulate bare metal, but rust and grime would be more prevalent on the surfaces. Of course, hoppers made of aluminum would be a different story, but those weren’t common in the steam era that I model. – Eric

  4. Nice work on these cars. Don Cassler once told me it seems red hoppers tend to look black inside and black hoppers tend to look rusty inside. As to window cleaner, I find it excellent for cleaning brushes, thinning acrylic paint, wetting ballast, and “freshening up” dusty scenery. I keep a bottle of Windex (preferred) or a store-brand handy in my shop.

    1. Thanks Gary! In some of the early attempts on these hoppers, I observed a similar situation as Don described. Rust stood out well on the cars with black interiors, but not so well on the cars with red or light brown interiors. That’s when I experimented with the layer of Krylon Earth Brown before the rust paint applications. The dull Earth Brown paint grimes up the interior and makes the other layers of weathering a bit easier to see. – Eric

  5. You will also find a certain amount of localized weathering on open hoppers, depending on how the car was last unloaded. The commodities carried in these cars tends to be quite abrasive and certain patterns can appear if the car was dumped by rotary dumper or unloaded through the hoppers. These can be quite subtle or quite obvious, depending on the length of exposure to rain and weather after unloading. Every unloading process exposes at some unprotected steel inside the car.

    The PRR once had a barge loading facility on the Ohio river in Pittsburgh. As a teenager, I often visited the small yard and was fascinated by the unloading process. They had a car shaker that agitated the load for faster dumping into the conveyor below the car. During the winter, many cars arrived with the load partially frozen and the cars were passed over a fire pit to help thaw the load prior to reaching the shaker. Once reaching the shaker, some coal would still be lumped together and this brought out the sledge hammers. The crews would hammer on the hoppers and side sheets above the hoppers until they, and the shaker would finally break the chunks free. Those hoppers went back to the empty yard with a lot of burn damage to the hopper bottoms, dents from the sledge hammering, bare metal spots and charred paint. The point here is not to forget to weather the exterior area of the cars around the hoppers and lower center side sheets. Small wonder hoppers had to be rebuilt so often. I suspect that hoppers unloaded by other means would show different weathering patterns.

    These hoppers were predominately PRR, C&I and BWCX cars but occasionally an intruder could be found. The scarring was most evident on the red PRR cars. The yard was usually worked by an H9 and the coal trains were usually handled by an L1, M1 or J1.


  6. Great looking weather the inside of the cars without having to use all different types of paint for the desired effect.I use sophisticated finishes rusting kit.just put down your base coat then after that dries apply the metal infused paint.then after that dries liberally apply the rusting the car or cars in a zip lock bag and leave in direct sunlight for several hours the moisture trapped inside the plastic bag will produce rust for as long as you leave it there

    1. That sounds like an interesting application, Cliff, but I find the hopper interiors are not just rusty. They are grimy with the remains of a previous load. Some of the interior paint may have failed to show raw steel that has not yet rusted. And not all rust is the same color. New rust is has a brighter look than old rust. I want to convey these other layers of interior weathering and use multiple steps with different colors to achieve this. While is sounds complex, once you work on a few cars the processes don’t take much time at all to transform the car interior. – Eric

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