"Grimy Black" is one of those old Polly-Scale "railroad" colors that remains popular today, so this this post is going to show you how to create an "airbrush-able" Grimy Black equivalent for about $.20 cents an ounce. This'll be a quick post though since I'm totally cribbing off of Gregory M. LaRocca's excellent article in the June 2015 issue of Railroad Model Craftsman (all due credit - and much appreciation - given).
Here's the skinny. First, you'll need paint. I used Apple Barrel brand that I got from WalMart for about $.50 cents for a two-ounce bottle.
You'll also need to invest in some Liquitex products - Airbrush Medium & Flow Aid. Total cost, about $15 (but it'll last you a long time).
Mix them all together, and Voila!! airbrushable Grimy Black. Here are my notes:
And since I'm not going to leave you there, here are the details. . .
I first mixed Apple Barrel "Pavement" and Apple Barrel "White" until I got it to match the Grimy Black I had on-hand (admittedly Badger's product rather than Floquil's, but it's all the same to my eye). FWIW, the ratio of "Pavement" to "White" is about 5:1. YMMV
That's a fine, inexpensive Grimy Black paint to bristle-brush, but if you want to air-brush it, a few more steps are required.
Next - as the article suggested - I used a Sharpie to mark my paint bottle into two equal parts:
I filled the bottom half of the bottle (up to the first mark) with my craft paint (in this case, mixed for a custom color).
Then I added an equal part of Airbrush Medium to the bottle, filling to the next mark.
Finally, I added 1 ml of Flow Aid. The article suggests ".5 - 1ml" but I wanted to be certain it would flow, so I used the maximum recommended amount. (It occurred to me later that the different range may be due to different sizes of paint bottle. The bottle I used is about 5/8 oz, so 1 ml of Flow Aid is/was probably overkill).
Once that was all mixed with my powered stirrer, I set my airbrush to 20 lbs pressure, test shot on a scrap of newspaper, and started painting!
I needed two coats for complete coverage, but the first coat got it to - I'd estimate - about 85-90% coverage. The acrylic craft paints dry quickly (I think the bottle recommends only two hours between coats), but I let it dry overnight anyway.
All of the "metal" girders on the overpass in the photo above were done using this paint and method (the "concrete" was done with an old rattle can of Floquil "Concrete" from my buddy Pete - and the fumes from that are what convinced me to try acrylics!)
And that's it! Maybe it's just beginner's luck, but this worked great for me - hopefully it will for you too.
A few quick notes:
- First and foremost - as with any acrylic paint - be sure to have a Q-tip or something with thinner on it at the ready to keep your airbrush tip clean. The main problem I had during this project was with paint flow stopping. Every time, that was due to paint which had dried at the tip clogging things up. Fortunately, a cotton swab dipped in thinner and twisted onto the tip cleaned things enough to get paint flowing again.
- Experiment with your pressures. At one point, I went as high as 30 psi, but only because I hadn't quite figured out point 1 above (cleaning the tip). You may be able to go lower than 20 psi, but I haven't tried that yet.
- Be careful if you shake the bottle or use a powered stirrer to mix the paint - you WILL get bubbles in the paint. I don't know if they'll be a problem (they didn't seem to be), but I'd rather they weren't there. I think next time, I'll mix the paint far in advance of when I need it, and then just gently stir it before use.
- I was really happy with the finish I got - a nice, smooth satin sheen - but I'm not confident enough with this method to go shooting locomotives (yet).
- Best tip of all: Practice and, if you're like me, do so on something that you can afford to mess up a little (i.e. it'll be weathered) and preferably near the back of the layout :^)
I hope you'll try out this method. And if you do, please let me know - especially if any other tips/suggestions occur to you!
(Full disclosure - after I posted this, and while looking for something else, I discovered a post I did almost exactly a year ago on airbrushing craft paint. Check it out for a different approach that uses Joe Fugate's recommended acrylic thinner with craft paint to airbrush it.)