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Piano tuning and restoring, french polishing

| Restoring the cabinet |Shellac |French polishing |

Piano Restoring: The cabinet

Some time ago, I had the opportunity to by a small grand piano, a 1927 August Forster 'baby-grand'. The mechanics of the piano were in reasonable condition, although one could hear some squeaks when playing some keys. The case once had been the farmiliar black high-gloss as one sees often in pianos. A previous owner had at some time tried restored it, and it probably was more difficult as he thought, because the surface looked as if it had been painted with black laquer and afterwards rolled trough sand. I decided, I wanted to restore the case properly, and I wanted to find out how people made such mirror-like surfaces in the old days, without using spray-cabins or other sophisticated technical apparatus. As it turns out, they used shellac, which is applied using the technique of french polishing to do this.


Shellac is a natural resin, produced eg. in Indonesia. Some type of plant there, defends itself by burying lac beetles that infest the plant, in some sort of resin. The hardened resin can be scraped off the leaves and is sold as shellac flakes in your local paint shop. This stuff dissolves quite well in alcohol, particularly if you grain it into powder. The brown liquid thus obtained, serves as a lacquer used traditionally to get the high gloss coat on pianos. The lacquer can also be obtained from the local paint shop ready to apply, it 's usually called just shellac or french polish (dutch: politoer). It's available in the natural orange-brown form, in a bleached transparant form. Also pigments can be added to get for instance the black shellac used in piano cabinet refinishing.

The trick of the shellac is that it dries really quickly because the alcohol solvent evaporates almost instantly. This allows one to apply many thin-film layers of lacquer quite quickly, resulting in a very even coat of paint, as opposed to the usual varnishes used in refinishing. It also prevents dust particles an hairs from setteling in the lacquer coat, so you don't need a dust-free spraying room. The final coat can be polished to high-gloss. A disadvantage is, that the resulting coat is somewhat fragile. It scratches easily, although these can be removed with polishing agent. And the coat is very sensitive to alcohol, as the shellac dissolves in alcohol. Rubbing the coat with some denatured alcohol and a rag, would completely remove the shellac coat within seconds.

Strip or Paint Over

Before the shellac can be applied, you have to decide whether to strip the old paint from the wood, or to apply the shellac over the old paint. Whenever possible leave good coats of paint that are already on the wood where they are, and apply the shellac over it. A risc however is, that the shellac and the old paint are not compatible. This means that the shellac does not adhere, or after some time, cracks appear in the shellac. Therefore, first, I try some shellac on a small piece of the piece, and leave it there some time (a week or so). I've worked over coats of acryl laquer with success. When the coat stays ok, I work the entire piece. Of course, painting over doesn't work if you are using transparant shellac. Otherwise we strip the wood using a generic paint stripping agent. This can be applied to the coat of paint, and after 15 min. or so, the paint can be scraped off.

Preparation of the Wood

Parts of the wood that have been stripped, now are colorless and have open pores and grain. First, color the wood using a black stain. Black stain is available in ready to use form (just black liquid, with a color) or you can get it in dry powder form (little bags), witch you can solve in alcohol or water. (The alcohol stuff dries faster, and I've had no trouble using it in combination with the shellac solved in alcohol.) (NOTE: I've had some trouble finding this stuff, because in dutch it's called 'beits', and this name is also used for some liquid agents that protect the wood from worms, from rotting etc. So, at first, I was applying coats of 'rambo pantser-beits' to my piano, which is not fit for that purpouse. The only thing the beits must do, is color the wood: you could maybe just apply liquid quink with the same result.) If the wood is dark, you will have less trouble getting it black with shellac.

Then, to seal the pores and close the grain, I apply a few wash coats of heavy shellac (which will not soak into the pores). Just wipe the shellac on the wood using a rag, or a brush, where you take care not to wipe an area twice, because this will tear up the coat. After half an hour or so of drying, sand using grid 280. Repeat the procedure until the surface is smooth. The surface will gradually fill with shellac. Then sand progressively to grid 400 or so. Parts of the piece that still have a coat of paint, just sand to 600. Make shure that all the scratches have been removed. You will now be able to burnish the surface a bit, leaving a smooth top.

French polishing

Now, you can build up a coat of shellac, in the process called 'french polishing'. I use the ready for use shellac that you can buy in your local paint shop (also called 'french polish' or 'politoer'). For the acutal frensh polishing, I thin the shellac using about 50 precent of alcohol. (For thinning, I just use plain 'spiritus', which is methyl-alcohol (85%) wich is used for cleaning, sells at $1 per liter, as the denatured alcohol you buy at the drug-store is rather costly, especially if you want to cover large areas.)

To apply the shellac, for small surfaces or corners, I use a small piece of cotton waddings. (Depending on the size of the surface.) Around the waddings I wrap an old t-shirt (part of it), in such a way that I get a surface free of folds. This is where you apply the shellac with. For large surfaces, I now use a piece of sanding cork, (a block of cork, size 3x6x10 cm). I wrap a layer of cotton wadding around it (about 1cm thick) and around that, I wrap an old t-shirt. This works really great for large surfaces, I used it on a grand piano (it was a small grand-piano though.)

Start with pooring a bit of thinnend shellac on the fold-free surface of the cotton ball or of the sanding cork, say 1 centiliter (a spoon full) for the sanding cork. I then use a piece of plastic, or paper, to distribute the shellac around the cotton, just rub the fold-free surface, work in the shellac. Now, if you push the fold-free surface on a clean piece of paper, it should just leave some shellac on the paper (the paper should get moist), It should however not leave drops of shellac. If it does this, rub the fold-free surface some more until it is just-moist. Or maybe, move the 'rubber' (the cork wrapped with cotton waddings and a t-shirt) around the paper, until no drops appear anymore. For frensh polishing, the condition of the rubber should be like a stempelkussen (english?) which is used to put quink on a stamp. It should be moist, but you should not be able to see any liquid, also if you push your finger into it.

Now, apply some lineseed oil on the prepared wood surface. Use some drops, maybe one drop for every 25 square centimetres. This will prevent the rubber from sticking to the wood, when you start applying the shellac. Now, rub the cotton egg on the surface using circular motions, applying as little pressure as you can. You will see streaks of shellac appearing on the wood, from under the rubber. Also the lineseed oil will get distributed over the wood. When just start to rub, there still is a lot of shellac in the rubber. To prevent the rubber from sticking to the shellac that is deposited on the wood, try to work around the wood as fast as possible, don't keep working in one place. This way, the shellac that has been deposited at one point, can dry, as you work at another point. In the beginning, when the rubber is still very moist, I usually make large motions (eg up-down) similar to when you are cleaning a window. When the rubber starts to get more dry, I make smaller circular motions, and work around the wood like that. You will notice when the shellac in the rubber is used up, as no more shellac will appear from under the rubber. At this point, I poor some more shellac into the wadding, and start the procedure again. This way, I apply maybe 3 or 4 portions of shellac. If necessary, apply some more lineseed oil on the surface. After this, the shellac coat will get a bit sticky, try to stop just before that. I then, usually whipe off the lineseed oil, then you can check the state of the work. And now let it dry for at least 1 hour.

When the work has dried, I check the state of the work. Are there any scratches, bumps or other roughnesses that must be removed? If this is so, apply lineseed oil to the surface, and then sand it, using maybe 400 grain or so (depending on the roughness of the surface). Sanding with lineseed oil is really great. First of all, the sanding doesn't produce any dust. Secondly, the sanding paper doesn't 'fill', you can keep using it a long time. Third, it seems that if I use lineseed oil when sanding, I get a smoother result, and get less accidental scratches. I usually use a piece of sanding cork for the sanding, and I pin the sanding paper on the cork. I usually just sand the entire surface, so that it seems smooth. (Don't sand away all the shellac.) The stuff that you sand away, now gets to sit in the lineseed oil, so what you end up with, is a surface covered in a black greasy substance. Before continuing with frensh polishing, I first remove the black oil with a rag, and I clean the surface some more, by applying some clean lineseed oil and whiping that away aswell, until all the black stuff is gone.

This way, I apply several coats of shellac, each with at least 1 hour drying pause. With each coat, the surface will get more smooth, the grain, and large scratches that were present, will get filled gradually. Depending on the roughness of the wood, you maybe need to apply between 5 or 10 (?) coats like that. It's maybe sensible, to wait somewhat longer between the first coats, as the shellac may 'sink into the pores' a bit. So the coat may appear completely smooth, but after a day or so, some grain-structure will appear again. Just leave the work for one or two days, see if it's condition is stable, and then continue.

When you've build up a sufficiently thick coat of shellac (this is the case, when the color is ok, and when the surface is as smooth as your sanding paper allows,) now you can polish the surface to a high gloss. I use two polishing agents for this, of decreasing coarseness. There are all kinds of polishing powders and pastes, but what works best for me is to use 'brasso' and a car-laquer reviver. 'Brasso' is a liquid polishing agent, which is used to clean copper. It contains a very fine powder does the actual cleaning. I use a mixture of 50% brasso and 50% lineseed oil, poor it onto the shellaced surface, and burnish the entire surface using a rag. Some shellac will be abraded (the rag will become black), and after burnishing, you will be able to see your reflection in the surface. For a final rubbing, I use a car-laquer reviver, which works like brasso, the difference being that the abrasive powser in the reviver is finer. I rub the entire surface with this reviver, using a ball of cotton wadding. After this operation, the surface has a mirror like appearance. The reviver I use, also contains some kind of wax, which makes the surface feel really smooth after burnishing.

French Polishing/Finishing Articles

I've collected some articles from the internet on french polishing. They are presented here.

Pete Taran's' article is the best. He uses pumice stone powder in the first applications to fill the grain. Gene Reynolds collected a few finishing tips including French Polishing for wood turning. From Handyman a guide on french polishing. Some tips on finishes from the ToleNet mailing list. Frank Weston posted a 17 step piano finish using shellac. Tons of grand mother's recipes, from finishes to soap, soup to ice cream from Paul Hubbs. An overview on various applications of shellac.

Restoring and Refinishing Literature

Philippa Barstow and Alan Waterhouse, "French Polishing." Batsford Ltd., 1995. Nice book that covers all the steps and some problems in french polishing, with lots of pictures.

John Hicks, "Shellac, its origin and applications." Chemical Publishings Co. Inc., 1961. An overview of shellac production and use in various crafts and industries. Contains a guide to french polishing, and a "piano finish".

Arthur Reblitz, "Piano Tuning, Restoring and Rebuilding." Dover Publications Inc., Exellent book that covers all aspects of tuning, restoring and rebuilding pianos. Emphasis on restoring and complete rebuilding.

Aidan Walker, "Wood Polishing and Finishing Techniques." Swallow Publishing Limited, 1985. Little book with a nice description on French polishing.

Other interesting link: www.Stillevenschilders.nl

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