Repair for damaged piano finish?

[Shawn Christ]

We placed a set of gum rubber drink coasters on the top of our piano for a few months and discovered this today. The finish has bubbled and is gummy to the touch. The piano is a 1980 Baldwin upright. I assume it is a lacquer finish but am not sure. Any thoughts or tips for repair?

[Shawn Christ]

Update: after further inspection it appears the bottom of the coaster softened and adhered to the piano. I can scrape some of it off with my fingernail. What can I use to try to remove it without causing further damage? Murphy's oil soap? Citrus remover?

[Rich Engelhardt]

Citris remover is going to be too strong.
I'd try something mechanical first, such as a plastic scraper. An old credit card would work well.

If you can find a very inconspicous place to test it - I've had a lot of success with VMP Naptha (or Lighter fluid) cutting rubber and leaving the substrate alone.
(kids leaving rubber bands laying on bedroom furniture & chewing gum left on the dog, etc)

Goof Off may also work - but - again, test it, test it test it. Goof Off has a fair amount of Toluol in it.
WD 40 may also work & not damage the finish.

[Shawn Christ]

Good ideas, thanks Rich, will give one or more a try.

[Harvey Pascoe]

With blistering like that it is mostly likely NOT lacquer but varnish which does react to some rubber products that way. Its repairable but you need some expertise to do it. Hopefully you can get the old blistering stuff off without affecting the stain, then build up as many layers as it takes to relevel the missing varnish, wet sand and rub out to the original sheen.

BTW, I recently set an unfinished box down on one of those rubbery anti-slip pads. When I sprayed the box with varnish, the octagonal pattern of the rubber pad was visible in the form of raised varnish. Really weird.

[Shawn Christ]

Harvey, I'm glad you posted this follow-up -- I think you are right on. I was able to remove the gummy mess with a plastic scraper, Goo Gone, and Goof Off per Rich's suggestion. The finish was in fact blistered, and now I have this depression to repair. It doesn't appear to me that the stain was affected. If you have any suggestions on the proper varnish and additional details on the procedure, it would be much appreciated.

[Scott Holmes]

Before you do anything else... A call to the manufacturer could provide a wealth of information.

[Harvey Pascoe]

Scott is right, it would be wise to verify the type of finish on there. Nice clean up job Shawn. I can't tell whether you've got discoloration there or whether its just the missing finish. The following procedure is the same regardless of finish type but I'm assuming its varnish.

Go to an art supply store or order on line a 3/4" flat sable art brush, the expensive kind costing $15+. Clean the area thoroughly with mineral spirits and a soft toothbrush to be sure you get rid of all rubber residue.

You should do a small test area first before proceeding with the whole thing. I would go to Ace hardware and pick up a 1/2 pint of their standard varnish. Carefully brush the varnish into the depression only, avoiding as much as possible putting varnish on the undamaged finish. The tricky part of this type of repair is not ending up with a hollow spot when when you go to feather it in with wet sanding. So build up the missing finish with as many coats as needed (allowing at least 12 hours between coats) until the depression is built up just slightly above the undamaged finish. You can hit it with the sanding block lightly to see how the buildup is progressing.

After you've done this, wait one week for it to cure. You will need 400, 600 and 1,000 grit wet paper and a sanding block that is perfectly flat, about 2" x 4". Very carefully start taking the new built up varnish down using short strokes with the 400 paper in such a way that you touch the original finish as little as possible. Be very patient in this level process. When you get it down close to the original, switch to the 600 paper and finish smoothing. Most likely you'll end up with a few low spots that you will need to add more varnish to, so you repeat the process until its level.

Looks like you do not have a gloss finish there but a rubbed semi gloss finish. You will just have to experiment using the sandpaper or a rubbing grit like pumice in order to duplicate the original texture. Finish up with the 1000 paper and see how that compares to the original texture, if its not a match, you'll have to figure out how to get there.

[Loren Hedahl]

If it is the original finish, I would expect it to be NC lacquer. There is a slight chance it may be shellac. This can be tested by the fact that shellac softens quickly with alcohol and lacquer quickly with lacquer thinner.

I've never tried filling in the affected area of a shellac or lacquer finish problem with varnish but perhaps others have. I'd wonder about seeing the 'witness lines' at the lacquer/shellac to varnish interface with the repair was complete. I have repaired small chips in the original lacquer with CA glue, but this is obviously not a small chip.

If it is lacquer, I'd say lacquer for the repair. You could even tint the lacquer if needed.

I'd say do your best to repair the damage locally, but if it turns out that the repair is visually obtrusive the whole panel will need to be stripped and refinished.

[Shawn Christ]

Tested and determined it's not shellac. Tried calling the manufacturer tonight but they were closed. Will try again tomorrow. Baldwin is now owned by Gibson Guitars and has gone through multiple bankruptcies and takeovers since 1980.

Interestingly enough, tonight I grabbed my copy of Bob Flexner's Understanding Wood Finishing and on page 138, in a nice yellow callout box, it says the following:

CAUTION: A lacquer finish can be damaged by extended contact with plastic materials, such as pads for tabletops and cushions for lamps and sculptures. The oily plasticizers in the plastic and in the lacquer migrate into each other, causing both to soften and stick together. You should not leave plastic in contact with lacquer for more than a few days at a time.

Very good advice. Guess I skipped this chapter because I've never used lacquer.

[Henry Ambrose]

Try some lacquer thinner in a less obtrusive area. A little rubbing with a rag damp in thinner will probably show some change in the finish. Once you get a feel for what happens, think about how to use that info to repair the damage. You might be able to mask off the entire top panel and spray it with lacquer thinner and get some reconsolidation of the finish. Alternately, find a good match and re-spray the panel after carefully sanding and blending your work in. Don't sand or scrape back to bare wood or you'll likely never match it.

[Harvey Pascoe]

No, one should definitely NOT repair lacquer with varnish. Varnish repairs when rubbed out will not leave witness likes, you only see those after sanding and before polishing.

Lacquer is easy to repair and you use the same method I described above. Stewart-MacDonald sells lacquer repair kits and some dyes that can be used to deal with color changes by tinting the lacquer itself.

Those rubbery non slip pads will do the same thing to varnish as to lacquer.

[Scott Holmes]

Harvey,
I hope you meant to say varnish WILL leave witness lines!

No, one should definitely NOT repair lacquer with varnish. Varnish repairs when rubbed out will not leave witness likes, you only see those after sanding and before polishing.

[Bob Wingard]

If you are a bit timid about the repair, you might try calling 1) a piano store to see who/what they use to repair damaged units 2) a larger furniture store .. same idea 3) a professional furniture refinisher.

It appears that the finish is gone, but the color remains ... that is a good thing ... you may be able to use lacquer thinner to "wash" the finish off without using strong chemical strippers, then respray with a matching lacquer.

A call to these guys might point you in the right direction ... http://www.pianoren.com/

[Nick Sorenson]

I would test to see if it's lacquer. I have no doubt that it is based on what it looks like. Lacquer is easily eaten up by rubber. Those rubber drawer liners you put in tool boxes do the exact same thing to a lacquer finish.

Also, there used to be something made by some lacquer manufacturer that was nicknamed "Baldwin Piano Lacquer". I can't remember who made it but I think it was Sherwin Williams.

Anyways, to test for sure, take off a cover or something that has a back side to it and put a drop of lacquer thinner on it. If it dissolves (since you already know it's not shellac) then you know it is lacquer. Lacquer would have been friendly for a production schedule like Baldwin had.

Beyond determining what it is, you still need to fix it. My guess on how to do that would be to rough the area up with 600 grit wet dry sand paper. You don't want to scratch the stain so that is where it will be tricky. But if you don't rough it up a bit, it would leave a witness line where you touched it up (in my experience). Sand bigger than the area you want to touch up. It's best to sand anywhere you think you might spray. Then spray about 4-6 wet coats of lacquer 1 hour apart. Let it set for a few weeks, and level sand it. Start at 600 and work your way to 1200 or so. I'm not sure how they got that sheen but I'd guess you could get close with steel wool and paste wax.