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Asphaltum, A Forgotten Finishing Gem!

Jun 29, 2016 | Expert's Corner | 0 comments

Many years ago, back when the dinosaurs roamed the earth, I had the privilege of working with two older gentleman in Charleston, South Carolina. Their forte was antique restoration as well as creating reproductions of the same. They went by the names of Jim and Bob, one was from Germany as I think, and the other from Sweden or Italy, I can’t recall. The language barrier for whatever reason was not an issue, even though neither spoke very good English. It was simply woodworking seem to create a universal understanding between us.  As close as I could determine they were in their early 70s when I met them. They had a very low-key, hidden little shop and the only thing electric was the incandescent light bulbs in the ceiling. Everything was old-school, lots of hand saws, old wooden bodied hand planes, molding planes. For me this was a dream come true, I was young and anxious to learn, I had my regular day job if you will, but I spent as much time as possible with them. I never got paid and in reality I thought I should be paying them. It is a time in my life I reflect on daily.

One of the things I quickly picked up on was their “concoction” that they seem to use on everything, it was used to stain, glaze and and worked quite well. The concoction was quite simply “Roofing Tar,”thinned with mineral spirits or naphtha. Depending upon the ratio of the tar to the thinner you could make about any shade of brown you wanted. I later learned it was actually the base for almost all oil base brown stains. They simply used, typically, linseed oil and the tar.

Over the years I kind of almost forgot about it, although I used it many many times. Several years ago I was reading a book by Michael Dresner, and he mentioned it. It brought back a lot of fond memories. However, somewhere through the years water base and alcohol dyes dominated in my work, and so the “concoction” lay dormant in my brain. A couple of weeks ago I was looking through the magazine that the Society of American Period Furniture Makers puts out. A gentleman had an article about using the Asphaltum for a glaze, and again the lightbulb went off. So to refresh my memory and have a little fun, I got some foundation coating without the fiber and started experimenting, suddenly my brain was filled with fond memories and superb results coloring wood.

As I stated, by varying the ratio you can create pretty much any color you want. In the photos you will note some samples, we were able to match, for example, Min wax Golden Oak, Provincial, Early American and so forth.

You will note that on the extremely sappy Walnut by applying a heavier concentration on the sapwood and allowing it to soak a bit then using a thinner mix over the entire thing we were able to blend the sapwood as well as give the Walnut a nice golden brown antique look. As most are aware Walnut lightens as it ages, not to mention most Walnut today is steamed in the drying process. This steaming causes the tannins in the wood to leach into the sapwood and color it. The purpose of this has to do with the fact that sapwood in Walnut is considered a defect. Steaming allows the lumber mills to have a better yield. Unfortunately, one of the other things it does to the Walnut is to make it darker, and in my personal opinion not in a pleasant way. When finished it seems to have a purplish tone to it, I am not a fan. By using a thin mix of Asphaltum which has the brown/gold tone to it we are able to overcome the purplish tint and have a nice color. One of the other advantages is that it will blend varying shades together to give a more uniform look. Works wonderfully.

Here’s a photograph of it used on quarter sawn White Oak, you will note that the bottom is obviously darker, the color above the darker section mimics Golden Oak. This is a perfect example of how you can alter the color to your liking by virtue of the ratio of the tar (a.k.a. asphalt) and the mineral spirits or naphtha.

Here’s some cherry that again by altering the ratio we can get whatever tone we want.

Here’s a strip of mahogany again varying the ratio it allows us to remain in full control of the color.

Here is one with a little twist, we used some General Finishes Cinnamon Dye as a base color then the Asphaltum over it, this allowed us to create the deep rich burgundy color that is very desirable for mahogany. In reality you could use the same technique on about any wood, it is especially nice on cherry as well. Not to mention you can color Poplar, pine or basically any secondary wood to match.

Try applying a heavier coat then a thinner coat over some poplar, exactly as we did on the Walnut sap wood, you will be amazed at how well it mimics Walnut.

To cut to the chase, by experimenting a little you will be amazed at the various things you can do. You can add it to your favorite oil and create your own “Danish Oil”. It also works excellently as a glaze, especially with carvings. You need to remember that a glaze is used over a finish, meaning once you have a coat of finish then you can apply the Asphaltum and using some mineral spirits or naphtha wipe off the excess leaving whatever you desire in the carving or all the nooks and crannies if looking for an antique look. In the event you get a color too dark again using some mineral spirits or naphtha you can remove the color until you get what you want.

One of the things you’re going to notice since we are using mineral spirits or naphtha is that it will dry back very dull, unlike a commercial stain where the oil is used, and will impart a sheen. The mineral spirits or naphtha allow it to act more like a dye than a stain, in my opinion that’s a really good thing, it also dries pretty quick, so if you plan to wipe it back to lighten the color do it as soon as possible.

One other thing when dealing with the tar, the foundation coating is thinner than the roof patch, but even then it’s like thick molasses, trying to pour it out of the can can be quite messy, simply dipping a stick in it or using a small dipper is the best way. You also want to keep notes and measure accurately so as to be able to match the colors in the future.

Irrespective of whatever topcoat you plan to use, be sure to allow the stain to dry well, if using a wipe-on oil, go easy so as to not disturb the color, after one or two coats of oil it will all be locked in. If you want to use a water-base topcoat I suggest a coat of shellac over the Asphaltum after it has dried just to be safe.

In conclusion, if you experiment a little you will be amazed at all the various things you can do, and by the way did I mention is extremely cheap compared to commercial stains?

As many of you may know, I’m finishing up writing a book on finishing and Asphaltum definitely has a chapter, it’s just one of those forgotten gems.