French polishing is one of the most misunderstood finishing methods that is wrapped in a mantle of mystique and misinformation. It is nearly a lost art, and that is a pity as it is an extremely useful finish that is elegant and remarkably smooth. There are a handful of woodworkers who make new furniture that is entirely French polished. This is a very time consuming process of filling and rubbing with many coats of shellac. There are others, like myself, who use it for finish restoration, for which it is perfectly suited.
French polish is nothing more than a method of rubbing on a shellac finish. The technique can vary, but the final finish is glassy smooth. It dates back more than 2000 years and there are ancient Chinese pieces that are still in very good condition in many museums. Shellac is a natural product that is an extract of insects collected in southern Asia. It is dissolved in alcohol and rubbed on with a pad, usually made of stretched cotton cloth over a filling of cotton or wool. The beauty of French polishing is that it lays down a very thin layer of shellac at each pass and fills the grain and imperfections without building up finish that has to be sanded off. So, it is self leveling.
Pianos and many antiques have been French polished for much of history, up to the middle of the 20th century. Shellac is still the preferred finish for some hand made pianos in Europe. French polishing can be applied over nearly any finish to achieve a high polish. Since it fills scratches selectively, I find it an ideal refinishing method that does not require stripping the old finish, filling the grain, staining, applying multiple coats of modern finishes, and sanding and polishing most of that new finish off again to achieve a high polished final product. Instead, French polishing builds on the original finish that was often painstakingly applied by fine craftsmen. In many cases, the original finish was shellac and French polished in the factory. Later, sprayed lacquer and then modern polymer finishes have replaced the hand rubbed finishes.
The photos at left show examples of piano restoration before and after French polishing. In some cases, multiple methods were needed to correct major flaws in the finish before the final French polishing. The classic problem is a flower pot mark on a piano top. Sometimes it leaves only a white ring, and in other cases, a wet vase can destroy the original finish right down to the wood, as seen below. These can be restored to original condition for a fraction of the cost of a full refinishing.