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Freelife,

Another "shimming" technique that has been demonstrated to work quite well is the one developed by Bill Spurlock using a router (or die grinder fixture) to machine the void that will accept a perfect fit "shim". This is in widespread use in shops.

Webb Phillips also taught about using a bisquit joiner to machine a square channel (rather than wedge shaped) down the board, but not going all the way to the ribs (if I remember correctly). The advantage here is that the adhesion area is three sided rather than just two. One would carefully cut 1/4" "shims" (though they are square) to fit tightly, and then raise the board with wedges just before gluing them in. Then when the wedges are removed the board compresses in nicely on the shims. He claimed great success with this method.

Of course this is all "for the future" if you so desire.

Peter Grey Piano Doctor


Peter W. Grey, RPT
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Wow! Chernobieff, piano411 and Peter Grey, this seems to have exploded way out of proportion. Glad I don't reside at the Capitol Building in D.C., or you might all be raiding and pushing inside with signs that say "New Soundboard Only," or "Shims won this election by a landslide," or "Stop the Soundboard Steal!" šŸ¤£

Too much focus has been on the second part of my Original Question: "in as little as a few months (in dry climates) or years, the cracks re-separate slightly, showing a new thin black line."
That's my fault, sorry. I agree with, and regularly perform, all the drying-out and jacking-up procedures mentioned here. But that was only a secondary concern. Please forget about that and focus on my original line: [My soundboard shimming] results always look professional with cracks fully filled & finished, but it's still easy to see where the cracks were." That's even with old-board shim pieces verses new-bought fresh spruce shims, meticulously stained to match the surrounding wood tone.

It's not a deal-breaker. All of my customers have been satisfied and paid in full. None have ever come back and said "I'm not paying because I can see where you shimmed and filled the cracks." But all of them would say, "I can definitely see the where you shimmed and filled the cracks."

I only brought up the painting/faux grain option because I've seen it done well, and, looking down through the strings, you could no longer see any trace of shimming or crack repairs. If no one else here knows about, or can recommend that process, that's fine. Peter's recommendation about Del Fandrich's epoxy-coat method may be the best option, and so much better than painting that it renders it superfluous. I will definitely try it on my next cracked board. But for my current Mason Hamlin 7' board, in which I already glued & sanded 10 close-as-I-can-get matching shims, before I just clear-coat it, I thought it was worth asking...just in case someone here replied "Oh yes, I know how to hide those perfectly, I do it regularly with a paint-over," or some other method.

Last edited by freelife; 01/10/21 06:08 PM.
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Originally Posted by freelife
I thought it was worth asking...just in case someone here replied "Oh yes, I know how to hide those perfectly, I do it regularly with a paint-over," or some other method.
No, I don't have any suggestions that would be of any value to your current situation. I don't have a problem with adding grain lines or whatever, since the board is covered with some kind of protection anyway. But, I guess the grain lines are already there, and are just different? I've added grain lines for other types of wood repair, but not in this situation.

The epoxy is fine, and it wouldn't have any negative effect on the sound. It is easier than a shim. But, you would be able to see that fix for sure. Unless, you go through a process of adding a faux finish and grain lines, which is fine too.

In the future, if you wanted the shim to match, I would try making your own shims. That allows you to split along the grain lines, instead of the normal shims that are simply cut. Then custom match and fit for your situation.

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Bill Spurlock used to advocate use of an air brush to color the shims to try to hide them. I never tried it. Bill's a pretty smart guy with good ideas and practices.

Otherwise, for pinpoint touch up, Mohawk sells a wide variety of stain brushes that come right down to a point. I use them regularly in furniture touch up. Very useful. That may be of use to you.

I think that's about it for my bag of tricks.

Peter Grey Piano Doctor

Last edited by P W Grey; 01/10/21 07:16 PM.

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Interesting discussion, thank you all. I am having a piano restored at the moment which has involved shimming the soundboard.

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Another thing you can do is to inform the client beforehand that soundboard preservation techniques are rarely invisible...and point out your handiwork, don't hide it.

Peter Grey Piano Doctor


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Originally Posted by P W Grey
Another thing you can do is to inform the client beforehand that soundboard preservation techniques are rarely invisible...and point out your handiwork, don't hide it.

Peter Grey Piano Doctor

I agree, show off your workmanship.


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Just a few years ago back in 1888 Hansing wrote a book that within its pages he described the procedure on how to properly shim a soundboard in regards to obtaining an invisible joint.

-chris


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If I was having a vintage piano restored I would prefer the original soundboard be preserved with expert shimming (if necessary) and would not mind the repair being visible. It indicates originality and disguises, such as painting, along with faux grain lines would look ridiculous.

To me.


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Obtaining a good fit with an "invisible" joint is not the typical problem (unless you're sloppy). The primary issue is the difference in color/appearance of new spruce embedded in 50-150 year old spruce. The aged wood is typically much darker than it was when it was new, and the new shims "stick out like a sore thumb". Thus, a reliable method of "hiding" is what is sought after.

One can carefully mask of each side of the shim, then apply an appropriate color stain (or colored medium to improve the contrast. This would best be done after the first coat of finish is applied to prevent bleeding into the surrounding wood as well as collateral damage in removing masking tape from raw wood.

I believe this is the OP's REAL issue. He can correct me if I am wrong.

Peter Grey Piano Doctor

Last edited by P W Grey; 01/11/21 08:55 AM.

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Years ago I brought in a grand for a rebuild and didn't realize the board had been painted until I started cleaning it off. It was very well done. The problem is it's very difficult to do a convincing job.

Shims can be invisible and long lasting, but it requires proper preparation. The board has to be dried down to a point that the cracks open up. The cracks then have to be trimmed enough to remove any discolored wood around the crack. I use Bill Spurlock"s system for that though I've used other methods as well.

The next step is the most important, wood selection. I keep a supply of old spruce of various colors and grains so I can match the original board. You want to pick a color that is the same or slightly lighter the the original board. It is also important to match the light reflection of the wood. I do this by applying paint thinner to the board and the shim and turning the shim back and forth to look for any color shifts. You also need to view the board from both the keyboard end and the tail end. You have to match the color shifts together. Once you see it you'll know what I am talking about.

When you apply your first coat of finish you'll see how well you matched everything. If the shim is a little lighter than the board, I will use Transtint stains to bring the shim into the final color match.

This was hard to describe and it's even harder to do, but you can make the cracks disappear.


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Thanks Bill. Probably the best and most 'on point' answer so far, based on what I asked.
Of course, in my current rebuild, I did not do some of the steps you are indicating, and the shims are already glued into place. But prior to clear-coating, the Transtint stains sound like a plausible way to better color-match the shims and make them at least little more 'invisible'

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Originally Posted by piano411
When Chernobieff Piano puts a new soundboard in his pianos, they no longer sound like the name on the fallboard. He may argue that he thinks they sound better, but everyone has their own opinion. Putting in a completely different style of board, just because he think it works/sounds better, is not the right thing to do. It is just his opinion. Replacing a Steinway soundboard with a Chernobieff Piano soundboard doesn't add value, in fact, it will notably decrease the instruments value and make it more difficult to be sold in the future.


How could i pass on this golden opportunity, in the form of an attack on my work, not to explain my work a little bit.

First piano411 is a username to HIDE behind. Chernobieff is my real name and i put it on my piano rebuilds because i am proud of the work i do.
Its fascinating to read such a comment from an individual, to the best of my knowledge, has never played on one of my instruments. Hmmm.

It wasn't hard to look at the manufacturers work, and find acoustic errors that are made. For example, the most amazing discovery of mine in 2019 was driving points. I learned about it from Keith Hill. When I looked into it further I realized that piano manufacturers totally violate this principle on every board. The driver of energy (in this case the bridge) should be in the center of amplitude of the panel for maximum efficiency. Think of your favorite singer singing when sick versus when healthy. If anyone wants to check for the center of amplitude(next time you have an exposed soundboard) put a dial on each end of a rib (4 inches out), then put a 10lb weight on the bridge over that rib. Both dials should deflect the identical amount. If not, then the rib is scalloped wrong, the panel is thinned wrong, and the stiffness distribution is wrong and the board will have an undesirable higher natural frequency.

Interesting side note. When you put in a good board in any piano, it takes on the sound of that piano, because of all the other links in the chain, rim, plate, string scale, hammers. Because a good board fulfills its acoustic function. A crappy board on the other hand could screw up that link.


-chris


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Originally Posted by Chernobieff Piano
How could i pass on this golden opportunity, in the form of an attack on my work, not to explain my work a little bit.
In all honesty, it was an attack on your approach. You unequivocally stated that replacing the soundboards was the right thing to do. You flat out called OP a lair, and implied that shimming has some kind of negative impact on the sound. You are wrong on all accounts.

My point to you was that if we asked Steinway to put a valuation on a piano after you replaced the soundboard, vs. if they had done the work, we all know that your work would be valued much lower. In fact, it may only have scrap value! I know the truth hurt, but it is what it is.That is the economic reality of the current system we find ourselves living in. Maybe your boards are better, maybe they are worse, but replacing a Steinway soundboard with you own design will have economic consequence for your customers should they ever choose to sell their piano in the future.

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