Rob Skinner's goal in restoring gas engines is to make them look as original as possible. To that end, he needs to paint the parts and then age them to the tune of a hundred years, giving new parts an antique finish.
Editor’s note: This article originally ran in the April 2010 issue of Hit & Miss, Journal of the Western Antique Power Association and is reprinted with permission of the author.
Selecting the type of finish for an antique gas engine restoration is a huge decision. It’s a lot of work, and you’ll want to be happy with it for a long, long time.
Such was my dilemma on my current project. It’s a work in progress, and at a stage in the project that might be of interest to Gas Engine Magazine readers. The engine has a lot of original paint, which I want to preserve. It’s also missing a few parts that needed to be fabricated.
Newly machined parts are really shiny and spiffy, and if left bare, are a testament to the skills of the craftsman who created them. On the other hand, my goal in restoring gas engines is to make them look as original as possible. To that end, I need to paint the parts and then age them to the tune of a hundred years, giving new parts an antique finish.
Aging paint isn’t really a science, per se, but a process in which the artist can employ any number of tools and techniques. The following are the steps and techniques that I used for these parts, but there are plenty of other ways to achieve a similar result.
The new parts were bare machined iron and brass. I was able to pick up some Rustoleum in a color that is very close to original. The painted parts looked very nice, and would go nicely on a new engine. My engine, however, is scratched, chipped, oil stained and looks well-used. The newly painted parts would not look right.
Old paint jobs often have several characteristics: chipping or cracking from age, blackening from being covered in oil and thinning from physical wear. A useful tool in obtaining these effects on new paint is fire. Judicious application of the torch can add a lot of years to a paint job in short order. It’s not easy to see what you’re doing, but if you goof up and burn off all the paint, it’s easy to just add more and start over.
The paint can be applied however you like. It doesn’t even have to dry all the way, as it will set up quickly when it’s heated. In fact, it’s a little easier to “distress” the finish if the paint is still a little soft. After the paint is ready, begin the antiquing process by using a carburizing flame to deposit a layer of soot all over the work. After that, the flame is neutralized and the work heated. The soot will cook into the paint and add blackness. Be gentle with the heat, as if you were soldering. As the surface of the paint starts to bubble a little, use a paint brush to apply some diesel fuel or light oil. It will flame up a little, but it will also wash the surface so you can see what you’re doing. It might be necessary to re-soot the surface. You’ll have to look at the paint that you’re trying to match, and use your judgement.
After the work has cooled a little, you can darken the appearance with the application of stove polish. The whole antiquing process is subjective, and there are many ways to achieve a desired effect.
Brass requires a different process to make it look old. Different alloys behave differently, so again, the technique will vary from project to project.
A quick and easy way to get rid of the polished “golden” look is to subject the brass to the fumes of hydrochloric acid. Pour pool acid (muriatic acid) into a container, and hang the brass piece over the acid. In minutes, the brass will darken. After it darkens, do not allow the brass to touch the acid, or it will instantly become shinier than ever.
Hydrochloric acid tends to leave a little bit of a green tint, and for this project, brown would be a little better, even though it takes considerably longer. Brown brass is obtained by rubbing the work with liver of sulfur, which can be purchased from art supply stores. It smells terrible, so keep it out of the house. Getting the proper shade of brown might take several days.
Rub the work in liver of sulfur, and let it sit. You can wipe more onto the work every few hours, as you find convenient. If you want a more uniform finish, after a day, wash the work in water and then polish it lightly with fine steel wool. Then start over again. Continue with the process until you’re satisfied with the results. You can forego the intermediate polishing if you’re seeking a less uniform result.
The painted work shown in these pictures took a couple hours, and the brass required about two days of waiting for the process to complete.