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A Classic Finishing Technique
© Frank Ford, 3/22/98; Photos by FF 3/5/95 & 2/28/98
In the days before spray finishing and abrasive buffing, the technique known as "French polishing" was said to produce the finest finish on wood. There's no doubt this is true since the alternatives were various forms of rubbed or brushed finishes.
Later, as the cost of solvents decreased and the cost of labor increased, modern spray techniques began to replace the French polish finishing. Around 1925 to 1930, the last of the American instrument makers gave up the labor intensive technique in favor of the spray gun.
French polishing is certainly the appropriate technique for finishing or for restoring finishes on the instruments of the 1920s and earlier. French polishing is a technique, not a material; the finish itself is shellac dissolved in denatured alcohol.
This is not a how-to method that will give you everything you need to become proficient at French polishing. I really don't think that is possible to do in print. The technique takes a lot of practice to get down, and I think it's a good idea to read everything you can about it. I'm presenting just an illustration of what French polish actually is, and how I approach it.
Since I'm an instrument restorer, not a builder, I'll describe the process of adding new finish on top of old to fill in wounds, irregularities, crazing, crack repair, moisture damage or wear.
My concern is preserving authenticity of old instruments. I really don't have any opinion of the tonal characteristics that may be attributed to different finish materials. One thing we all agee on: shellac French polish is certainly more delicate and easily damaged than the modern lacquer or catalyzed synthetic finishes. On the other hand, it is one the most easily repaired finishes.
So, here's the old time method, as I know it.
First, because this is an old instrument with a very dirty finish, and because I want to level the finish over some old crack repair and scratches, I'll sand the surface with 280 grit silicon carbide paper and a cork sanding block:
This is generally known as "scuff" sanding to prepare the surface for more finish.
Here's how it looks after sanding:
Almost all the surface has been scuffed, and the few shiny spots are dented areas.
My finish consists of dry shellac flakes (10% by weight) dissolved in denatured alcohol. I've added 1% by weight of the hardest natural gum, called "sandarac." Gum sandarac gives the finish just a little extra elasticity, toughness and resistance to scratches.
This is my applicator:
It's a pad made from ordinary old (to avoid lint) cotton bed sheet which I folded into a convenient size.
I'll wrap the folded pad inside another piece of the same cotton cloth:
I just open the cover and pour on a little of my shellac mixture from time to time as needed:
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