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Author: Subject: French polishing
katakofka
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[*] posted on 8-10-2017 at 09:31 AM
French polishing


Dears
I have been trying to get info regarding french polish on oud. I am aware that most luthier do not prefer putting any finish on the soundboard because it prevents the vibration of the soundboard. Shellac, however, is known of being an elastic resin and violin or guitar makers add many coats of shellac on their instrument soundboard to make the sound better !
Why not on ouds and if any has experimented many layers of shellac and saw a bad or good effect please share your knowledge if possible.
Also, what about luth, historical luth? Are they french polished classically?
thanks for any feedback
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SamirCanada
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[*] posted on 8-10-2017 at 11:40 AM


Also the best classical guitars are finished with shellac. Of all finishes, shellac is the best for soundboards because it doesn't penetrate the wood at all. It is simply sits on the surface. I am not sure it is elastic because it dries very hard.

On a soundboard the first "sealing" coats of shellac should be applied without any oil. after a few layers its ok to use a bit of oil to lubricate the French polishing pad.

I think one of the main reason not to finish a top is to promote the aging and drying... on the flip side it does offer some protection to the very soft wood. I would be hard pressed if anyone can tell the before and after sound difference between lightly varnished with shellac and bare wood.




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jdowning
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[*] posted on 8-12-2017 at 10:09 AM


Traditionally violin makers apply an oil varnish to their instruments not shellac varnish or French polish as far as I am aware. They may also apply a preliminary wood sealer or 'ground' prior to varnishing which, in some cases may be prepared from egg white.

The Turkish oud makers, who traditionally did not apply a finish to a sound board, apparently were very careful to avoid any oil contamination of the sound board - some going so far as to not allow anyone else to handle a sound board in the final stages of preparation for fear of contamination that they felt would adversely affect sound production.

As for the old European lutes that still survive after 3 centuries or more nobody is quite sure from the smooth uniform patinated oxidised appearance of their sound boards if some kind of transparent sealer was originally applied or if they were left unfinished. Otherwise the old lute sound boards were not varnished. Some have suggested that a sealer prepared from egg white may have been used but there is no historical evidence to support this theory as far as I am aware - although some modern luthiers have tested using this material as a sealer.

To avoid sound board staining I have finished some sound boards with a very dilute sealer made from shellac dissolved in alcohol (very much weaker than would be used for French polishing) - simply wiped on with a cloth. Shellac is not a very durable finish but does have an advantage in that it is easily repaired if worn or damaged. A disadvantage is that it has a limited shelf life once made up after which time it will not dry - so best to make up fresh solutions from shellac flake in alcohol. Store bought shellac varnish should be tested before use by applying a drop on a sheet of glass - it should dry hard in a short time if suitable for use. (Shellac also will not dry if applied directly over some oily tropical hardwoods unless they have been chemically degreased beforehand).

Shellac varnish is a very ancient type of wood finish but I am not sure if it was ever used on lute or oud historically in place of more durable oil varnish. Of course no old ouds survive prior to the 19th C to verify if this is the case but perhaps French polishing of ouds is a more convenient modern technique?
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katakofka
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[*] posted on 8-12-2017 at 11:14 AM


Dear jdowning
thanks for your valuable comment on the subject
I am not sure if French polishing is a modern technique for ouds nowadays for the simple reason that it is a heavy duty time consuming application. Polyurethane, lacquer seems to be more convenient for the makers especially the ones having mass oud production. The trend is now lacquer or polyurethane bowl, polished with a car polishing material to make the instrument shining. I have seen some doing shellac coats on the soundboard as well.
Still wondering how many have tried a complete french polish on a oud with several coats (>100)
Best
SY
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