It goes without saying that railroading is a very dirty business. All railroad equipment is subjected to the elements and is seldom if ever washed unless it is a part of either a crack passenger train or the company's publicity mill. But weathering is something that we don't seem to want to do to our models upon completion. I mean, we spend a lot of time making sure that things look just right in terms of assembly, painting and lettering; why would we want to "mess up" all of our great work?
The pictures presented here give some compelling reasons why we should consider messing up our rolling stock. Because it simply looks more realistic and that is the look we are stiving for with our railroads... realism.
Take a look at how some time spent weathering these older freight cars just makes them look better when they are set in their surroundings. The techniques used here aren't really all that hard to learn if you are willing to practice a little on some older cars in your collection. For most of us, the slather & wipe process would be about all we would need to use. Simply take some appropriately colored paint, thin it down a little then slather it on the car. Next, before the paint dries, take a rag or paper towel and simply wipe off about 75-80% of what you just put on. Work with the general direction of gravity meaning basically up and down as the dirt & grime would tend to wash down from the top of the car. But if you are working on a stock car with horizontal boards, you can work along those boards as well.
Another technique that I like to use is simply diluting India ink with some isopropol alcohol and painting that all over a car. The ink tends to pool & puddle on the car as it would in real life giving satisfactory results. Others have used powdered pastel chalks that they then seal with an overspray of a clear paint. For more fine detalis, you can use very sharp colored pencils; these work great for white chalk marks or to highlight an individual board or two.
The roofs and tops of cars got especially dirty in the steam era. Nothing like a good coating of soot to get a car quickly dirty. Note also that the weather takes its toll on the materials that the car is built with. In the middle car pictured above, the "new" roofwalk boards are simulated by painting a few of them with a lumber color. Of course, that gets a good coating of "soot" as well.
Weathering can vary from locale to local although cars do tend to get shipped all over the country so those weathering colors can be mixed up a bit. Keep in mind that variety helps highlight individual cars so a really dirty car among several other "sort-of" dirty cars will really stand out.
Grab an old car and have at it. It won't take long before you get the hang of it and will be messing up your rolling stock left & right!
A special thanks to my friend Eric who graciously allowed me to use his pictures!