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#1989720 - 11/22/12 10:36 AM finish question  
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msks Offline
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lawrence,KS
I have a 1908 Bechstein upright to redo. The original finish was black and glossy. It does not seem to dissolve well with alcohol. Also , there is a clear layer underneath which does not dissolve easily either. What do you think this could be??
THe surface has checking so it has to come off. I am debating what to put on this piece. Suggestions?

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#1989768 - 11/22/12 01:43 PM Re: finish question [Re: msks]  
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If it is indeed the original finish, it would have been shellac. Old shellac is easily removed with a scraper, followed by sanding. I would not try to dissolve a shellac finish, it is way too messy.

Your situation may be different, as black shellac was usually applied directly to the wood without a clear undercoat. I suspect the piano may have been refinished at some point. In that case, I would experiment with chemical strippers.

#1989774 - 11/22/12 01:48 PM Re: finish question [Re: msks]  
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Well, it would have been some sort of spirit varnish, probably not pure shellac. If the black is mostly intact, you might look into repairing the finish by French polishing.

(Appropriate for Chopin, who was French-Polish!)


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#1989808 - 11/22/12 03:04 PM Re: finish question [Re: msks]  
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No matter what method you use to take off the old finish (we always use a chemical stripper [Jasco] from Lowe's), I would recommend completely disassembling the case, if you haven't done so already. The more tight corners you can eliminate, the better the results you will achieve. Chuck Behm


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#1989813 - 11/22/12 03:48 PM Re: finish question [Re: Supply]  
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The woods in the case are definitely not the same , so it was originally black. THis stuff is much tougher than typical 100 year old varnish. Perhaps as you say a spirit varnish. THere is too much damage to repolish the existing finish,also checking.

#1989838 - 11/22/12 04:50 PM Re: finish question [Re: msks]  
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What does the checkering look like? Is it like snake skin or larger pieces of checkering with long lines and broken into square pieces or rectangle pieces..….

Some of the modern cat lacquers are furniture grade lacquers that don’t do well as a piano finish.

Might not be the original finish. The undercoat could be a flexible vinyl seal coat if it has been refinished.

Try touching a corner with methyl hydrate or lacquer thinner. Methyl will melt shellac or varnish. Lacquer thinner will cut through them all I believe.

If you can’t melt it then 80 grit on the palm sander, mask and plugs…don’t forget to turn on the exhaust fan…..


Dan Silverwood
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#1989867 - 11/22/12 06:36 PM Re: finish question [Re: msks]  
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France
I have seen old black laquer that did not react well even to stripping, a lot was due, the undercoat, whitish, is a mistery, it could be some kind of plaster with some skin glue, does not react well to paint/laquer removers products based on solvents (but water moisten them.

The lacquer could be an old cellulose based one, it harden enough in time to be difficult to strip

I better sand them then do French polishing, as the undercoat often can be kept. if not cracked I use the shellack without full sanding.

BUT ... lot of small parts on a vertical, around the fallboard, the music desk, etc. the piano have to be totally dismounted to make a better job.


If not I use copal in the corners, then when French polishing i mix the strips left with the rest of the varnish. it is discrete enough usually (corners are alxays a problem, the shellack based lacker can be brushed but it is too thin and it burns on itself if brushed twice, the copal is thick enough (and shines in one pass)

There are special shellack based products that can be used in 2 passes only - 48 hours. They get thick soon and shine well but not really very long (possibly 10 years...)
May be with a normal shellack based coat as final in the end.
those "easy to use" French polishes dont raise more than they can, it is not possible to make more than 2 coats
They are easy, as you only have to turn, and turn, they dont burn, you turn until it begin to shine (can take some time )
Those producst are well resistive to alcohol when you rub, it can be a good way to learn how to do later with normal French polish

Anyway a clear gloss shellac is used as soon the case is black enough. the same day or on another pass.

Then when cleaning the piano the cloth does not get blackened.
The clear lacquer (filtered) have a higher gloss than the black one, also..


Last edited by Kamin; 11/22/12 06:54 PM.

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#1989870 - 11/22/12 06:50 PM Re: finish question [Re: msks]  
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One can go through the full French polishing process, using black pigment to smooth and fill the cracks and gaps in the old finish to restore the original finish.


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#1989912 - 11/22/12 10:03 PM Re: finish question [Re: Silverwood Pianos]  
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The lacquer thinner does not melt it much. The checkering is the lines and rectangular sort at the wood surface. It seems it will need scraping & sanding to remove it.
I am not clear on the shellac products you refer to Kamin. Is Qualasole what you mean? Are these available in the US? I haven't seen these.

#1990023 - 11/23/12 11:08 AM Re: finish question [Re: msks]  
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If lacquer thinners will not melt the finish then you are looking at some type of plastic or poly type of finish. Long lines with rectangular pieces is too much catalyst in the mix or too cold when sprayed with a plastic type finish. I would suspect the former is the cause.

Dichloromethane can re-activate some types of plastic finishes and cause the catalyst to cure once again making the finish really brittle so you can chip it off. I removed a poly finish this way. The chemical reaction made the finish look like a broken windshield; lots of small glass-like chips.

You have to leave the stripper on for a number of hours for this to happen. Might work there or might not. Difficult to know when I can’t see what you have there.


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#1990035 - 11/23/12 12:31 PM Re: finish question [Re: Silverwood Pianos]  
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hello Dan . I know you do much more refinishing than me but I was told thaat an old cellulose based lacquer can be very hard to strip and not react immediately to paint thinner or acetone.
dichloromethane is a major component of stripping products if I read well.

I will try to know what kind of black lacquer was used in those times. catalysed may appears later than 1908 I suppose...

cellulose have been mixed with shellack in the finishes from the post WwII , May be beforethen also...


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#1990081 - 11/23/12 03:26 PM Re: finish question [Re: msks]  
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In my (limited) experience, dichloromethane is a critical ingredient for managing some finishes. Not all finish strippers contain the same ingredients. One should read the product description. Here in South Africa, one well-known brand of stripper contains dichloromethane, but several others don't.


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#1990160 - 11/23/12 10:34 PM Re: finish question [Re: Silverwood Pianos]  
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The last time this piano was 'worked on" was about 1950, in London. THe black layer is older than that. Likely the original from 1908.

#1990213 - 11/24/12 05:15 AM Re: finish question [Re: msks]  
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Originally Posted by msks
The lacquer thinner does not melt it much. The checkering is the lines and rectangular sort at the wood surface. It seems it will need scraping & sanding to remove it.
I am not clear on the shellac products you refer to Kamin. Is Qualasole what you mean? Are these available in the US? I haven't seen these.


hello. Sorry I don't know the kind of products available in US

Those recipes contains thick resins and fast evaporation solvents, but still are considered as Shellac and alcohol polishes

They contain some waxes from the shellac and some thick "copal"http://en.wikipedia.org/wiki/Copal (vegetal resin very shiny but thick) that quality is employed : http://artdec.ca/boutique/copal-de-manille
while the the shellac used for final clear coats passes is filtered (un-waxed) .



So they build (thicken, the layers grows up) soon and close the grain well (closing the grain is long if done the traditional way, hence the use of rabbit skin glue, plaster, talcum different powders in a media before polishing.

Those polishes (Venitian polish, Furniglass, Mono, for the French products) can be less hard in the end (so less shining)

you may find some in England. I would not make a black shellac for a customer before being sure my time will be paid, but I have no problem to sand a little , then apply a new coat of black polish. Sometime you can even polish the case with alcohol and really very little polish.

Once the old silicons and other products often find on old pianos are cleaned, the alcohol can rub the surface well, a drop of oil may be necessary.



Last edited by Kamin; 11/24/12 09:32 AM.

Professional of the profession.
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I wish to add some kind and sensitive phrase but nothing comes to mind.!
#1990244 - 11/24/12 09:40 AM Re: finish question [Re: msks]  
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Hello Isaac,

Yes dichloromethane is the active ingredient in the paint and varnish remover I use. Sometimes the stripper has to be left on for a while. I have never had a lacquer finish that will not come off.

You are probably right about the old cellulose lacquer.


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