Bill Davis wrote me about an ongoing project of his and how he wanted to learn more about how to represent the oil soaked dirt and crud that collects around journal boxes like the one below and on track where diesels stand for long periods, such as in an engine terminal.┬áBill is an excellent modeler, who doesn’t need my advice on the technical stuff, but perhaps feels less confident on the artistic stuff like weathering.


You can see the buildup of oil soaked dirt on the bottom of the journal box and on the face of the wheel, where the oil has sprayed out of the journal from centrifugal forces of the car in motion. There’s lots of other neat things to see under here but I’ll save those for another time.

I mentioned that I’ve had success with dusting powdered chalk into wet paint.

Tamiya Nato Black with Mig Gun Metal weathering powder

It’s a simple process to do. You just apply the paint to an area and then dust on the powdered chalk directly by scraping a pastel stick with a knife blade while holding it over the wet paint, or you can also dip a brush into a pile of pre-scraped dust. Commercial weathering powders also work.

The chalk dust provides the 3D texture seen in the prototype photo while the paint acts as the binder. Sometimes I will apply a second wash coat of paint with more powder if I feel more buildup is needed.

Oil soaked dirt buildup around journal box on a National B1 truck

Admittedly, I might have gone overboard on this truck. And yes, the wheels still rotate freely. As always these things are a judgement call, even when working from prototype reference photos, which is always a good idea.

Like all of us, the only thing Bill needs is the confidence that comes from experimenting. As I said, he is an excellent modeler and just needs to plunge in to an area that still feels new and do some non-critical practice pieces to develop his skills. That’s advice your author would do well to follow too. I tried to shoot a video to demonstrate the technique but my bare bones video camera doesn’t do close-ups well and there’s enough bad video out there already.