Soundboard CPR

Hi all - Like to have a look at our down-and-dirty method of bringing a so-called "dead" soundboard back to life? It's quick, easy and doesn't require any fancy tools! Click here to see our latest photo journal of a 1900 Schiller upright rebuild posted on my website which features pictures of the techniques we use. It works especially well for pianos which have chronically loose ribs! Have a great holiday season! Chuck Behm

AMAZING! Thank you so much for posting! I enjoyed looking at the whole album.

Hey thanks, Ryan. The method we use for gluing ribs down seems to work really well for improving crown, better than any other method I've tried, although I'm not quite sure why. I'm guessing it's because we're using the back posts to tension and pull back on the soundboard while the glue sets, it wants to spring out once the ribs are glued tight. I just know that when I cut the wires the next day, the tension releases with a BAM! BAM! as you cut each wire, and you can see the soundboard visibly swell out.

Some things that you try in the shop don't work out as well as you hope. This method works far better than I ever imagined it would. The looser the ribs are to begin with, in fact, the better the results. We're nearly done restringing the piano in the photo set, and the resonance is really something - especially considering how dead it was to begin with.

In the next photo sets I'll have some shots of the cosmetic repair to the back posts using wood epoxy. The pin holes which were drilled come out nearly invisible.

Again, thanks for the comment, and have a great holiday season. Chuck Behm

I have a long way to go in learning the art of piano rebuilding.
Thanks for sharing your techniques and photo journal with us.

Hi Dan - The fact of the matter is that if you're taking the time to bring a vintage piano back to life, it's absolutely essential to consider the condition of the soundboard. If it's not in top form (which is rare on older instruments), ignoring it will make all your other work pointless, unless what you're after is just a nice looking piece of furniture.

The good news is that soundboard repair is ordinarily not terribly complicated, and requires only simple tools and materials to accomplish, as is evident in the photo journal of my original post. Removing the plate from the piano is necessary if shimming and refinishing is to be done, but that's really not all that complicated either if the case has been disassembled for refinishing

With a bit of work, a cracked soundboard with loose ribs can be put back in good repair, and the payoff is typically a huge improvement in tone and volume.

We usually finish off a soundboard repair job by attending to the backside (or underside, in the case of a grand) as well, as explained in this article from the Journal ( Tending to the Finishing Touches), which not only gives better protection from the elements, with a fresh finish on both sides of the board, but greatly improves the appearance of a board which has been repaired.

Obviously, an even better result could be had by replacing an old soundboard, but a small shop such as mine which is not equipped for such extensive work, very good results are obtainable with much more simple repairs.

Thanks for the comments, Dan, and best wishes. Chuck Behm

Hi Chuck,

I enjoyed looking at both photo albums. It is satisfying to see these vintage pianos restored to their former glory. The transformation can be quite dramatic from original to finished product and many clients are shocked at the results. Nicely done work by the crew there.

Thanks for the enlightening gallery of photos. I will pass this along to my piano technology professor.

Thanks, Dan and Dave - Several technicians have contacted me privately with questions about how I set up the wire and half-round clamps. Here's the answer I sent them, hopefully it will make the procedure a bit more clear:

Hi xxxxx - It's not terribly complicated. First, glue (I like Titebond, or Bouldoc's acoustic wood glue) is worked into areas of separation (between the ribs and the soundboard) with a narrow piece of veneer. Wipe off the excess.

Next, starting from one tuning pin driven into a post, piano wire is threaded through a hole in a rib and the soundboard, around a half-round on the top side and back through another hole about 1 1/4" away along through the soundboard and rib. It's then attached to another tuning pin driven into an adjacent post and tightened up until glue squeezes out from the treated area.

Or, it can be done with 4 holes in a row by going from the post through the first hole, around a half-round and back through a second hole. Then, instead of tying it off, it goes around a half-round on the post side of the soundboard, back up through a third hole in the soundboard and around a third half-round. It then comes through the fourth hole in the soundboard and rib and is tied off at the second tuning pin. So, two tuning pins, three half-rounds, and four holes.

The wire is tightened at the tuning pins anchored in the posts until squeeze-out occurs. The method works great with a two hole set up, and okay with a four hole set up, but is a little more work with the extra holes as the wire needs to be coaxed through the second and third holes a bit. It's somewhat like trying to tighten up shoe strings by just pulling on the ends of them - it works better if you tighten them up along the way.

I don't think that more than four holes would work very well. Too many friction points for the wire to really tighten up.

I do this procedure with the room really dry - preferably in the winter when the heat's on. I'll have a couple 40 watt bulbs under the piano (it's on its back on a cradle) for a week or so before the procedure, so the wood is good and dry. Once the glue joint is set between the ribs and the soundboard, I add moisture to the air by watering all my plants (we have a bunch of patio plants we keep in the shop in the winter). Simple method, but it seems to work.

The next day when the wires are cut, the soundboard swells visibly. With the bond between the ribs and the soundboard tight, any increase in the moisture content of the soundboard will cause it to bow outward, like the bottom of an old-fashion oil can.

Once this procedure is done, the cracks are shimmed. No point of shimming cracks while there is any looseness between the soundboard and the ribs.

I hope the explanation helps. If anyone has any further questions, please ask them here so I can answer for all to see.

Have a great New Years all! Chuck Behm

Thank you for that document , I will have a look ater.
To insert glue, what was used is the metal piece used in women underclothing before WWII (in metal, but I heard some where done in Whale teeth .

I was given an excellent tip lately : as the space to pour glue is so thin sometime, if you have an old metal rule , the kind that is rewind in a box, you can dismount it and the spring inside is avery thin and resistant blade that can pour glue in thin places.

the pressure is then installed from the most open side to the opposite, so tu push the glue.

I dont know what method you use, I made rib clamps with a curved shape, a little long, with 3 tuning pins for instance, possibly even longer clamps could be used.

In soundboards there is a part of the elasticity that is due to the glue joint between ribs and panel, and between bridge and panel.
This is the part that connot be restored, in my opinion, may be the use of a first grade hide glue can help adding a little stress (good hide glues are incredible in the way they tense the material they glue) I was lucky enough(§) to reglue all ribs on a small old grand (totally unglued) and had a really differnt result from the usual rib reglueing (with more of the "recent piano" tone (hence more dynamics)the soundboard gained some boom and resiliency certainly.

WHat a friend explained me is that because the wood age, the panel get smaller, so when he repairs old fortepianas, he add some wood to the panel to correct that.
If the whole panel is alittle smaller probably only a complete regluing of the ribs (and the bridge ?) can reinstall enough resiliency.
That does not mean an old panel is getting a little more life when repaired, but I never find them accepting more downbering after the repair, if only shims and local rib gluing is done.

The DW seem to be better but the panel lower where it was precedently after some time. Adding downbearing only for a few years is probably less good than doing nothing.

Raising the board curve certainly is the way to go, but lowering the plate, no in my opinion.

Best regards

WOw ! that is totally the opposite of what I do ?

My cauls are 30 cm long more or less (some longer, others shorter) and crowned on the sound board side

Initially I used the SPurlock caul style, so no added holes, the wire pass in the crack on both sides of the rib, and is inserted from both sides in a tuning pin (the tuning pin hole may have to be enlarged a bit.
That gives twice the tension of a single string.

There is an opposite caul on the string's side , on the panel.
That one is curved in the wanted curve (this is absolutely not computed, but I know I should.

Once the rib is glued the curved shape is kept.

I have a 30 years old glue in sheets, really strong, that stay liquid for a few minutes. It harden a lot, possibly I should add some skin or fish glue to add suppleness but I did not.

Gluing using such glue is not really easy, the piano is kept in atent and air mosture lowered to 20% (with some damage to the case,and possibly the braces gluing, the pinblock is kept enclosed in plastic sheets with moistened cloths so it will not dry).


I dont get the reason why you push the soundboard as if the strings where on ? may be you are right but I dont see the advantage ?

Do you believe that crowning the panel will make it too stiff ?

best regards

Thanks for the questions, and the description of your techniques, Kamin.

I realize that the method I'm describing might seem opposite of the desired end result of a crowned board. However, keep in mind that a soundboard will bow outward naturally if the ribs are glued in place when the board has a low moisture content. As the wood of the soundboard takes on moisture from the air (after gluing) and swells across the grain of the wood, it is forced to crown by the fact that the ribs running perpendicular to the grain, are not going to match the change in dimension except by bowing outward.

As far as holding the soundboard back temporarily, as long as a "spring" outward has developed as the board takes on moisture, that spring will still be there when the wires are cut.

Think of those big 8" (or so) springs used on the bellows of player pianos to hold them open. You could take one of those springs and forceably close it with a vise and tie it shut with a sturdy twine. Leave it shut for a year, a decade or a century, and what will happen when you cut the twine? It will spring open, of course. The springiness of the spring (so to speak) is not going be affected by the fact that it's been tied shut for a period of time.

The piano wire and clamp system temporarily holding back the push outward of the soundboard (once the bond between the ribs and the soundboard is set), does not diminish the crown once the wires are cut. You'll see the board visibly swell outward as the wires are cut. You can release the tension on the wires gradually, by turning the tuning pins they're anchored to, or cut them for a more dramatic effect - they'll "Bang" as they're cut.

Kamin, I'm no physicist. I just know that I've tried it, and in my experience it works.

Opinions vary, of course, and I'm sure there will be plenty who think I'm nuts (my kids have been telling me this for years, so I'm used to it!) Such is life. Chuck

I don’t believe it would matter if the soundboard was drawn to the rib or the other way around. Perhaps both are happening at the same time and not visible with the eye.

When two pieces are drawn together with resistance between them, if one side stops moving toward the other, the other side will instantly take up all the movement.

Once the two pieces are together they would return to original shape for the most part. There would be some deterioration of the original form naturally.

I have never thought about that too much; just pull until the glue squeezes out which is the result desired.

Thank you for the answer, Chuck. I would trust the drying of the panel, for sure . Indeed the crown can raise as much as possible in the treble and the high medium part, then in the mediums if that mean having a too rigid panel it cannot help.

What I noticed is that resistance to the strings is never raised in the mediums. If the panel is sounding better when unloaded that is yet a good result , if the boom is better, the tone will be better (assuming one does not lock the panel with too much downbearing)

The rise due to drying then back to normal, is not so large, but possibly it will depen,d of the initial construction of the SB (flat or curved rins, flat or curved press caul)

That is may be a good idea you had, Chuck, the ribs are now weak in their normal work direction, asking them to react to an opposite force may give a panel that have more stress at the glue joint hence more reaction..

Did you measure the crown before and after ? tap test and boom are good enough for the rebuilder but measuring is giving more data to think about.

But you count on the dimensional change of the dry panel to react with new moisture, and this does not seem to be very effective with old wood, probably compression set did take place too much.

A reverted crown soundboard (or a flat one) could work as nicely in fact, (as long as the panel is lively enough by itself) but the problem lies in the strings to bridge contact apparently.

Also, the rib regluing represent a little dimension in the case of that vertical. What happens to the downbearing ?

What I have tried is the use of milk of hot glue on the panel, used to fine sand the panel, but also for the tensionning of the surface (BWT I seem to notice a moistening of the top of the panel in some factory videos, no explanations at that day may be only to avoid cracks or burning of the panel)

I have been told that adequate hard lacquer can help to gain in tone, more partials, with a lacquer that flow and self tense well (as PU)..

Because the top of the panel is "expanded" the wood tend to loose particles, and that is why soundboard varnishes are used, (old fortes that have no soundboard varnishes are find with avery porous surface, after time passed)
So a product that can add cohesion to the panel and impregnate the wood enough is certainly what is the best choice.

The panels from some top brands are impregnated relatively deep with varnish and hard undercoat. I know the weight problem is often stated, but if a coherent thickness of a hardened product is used the piano can have more brillancy.

The regluing of ribs with shaped cauls on the panel side is effective, crown wise (because the shape is kept by the glueing)

Tone wise I always have thought it only can go for the better, but this may be difficult to evaluate.

Whenever possible I try to counteract the S shaped form that longer ribs take with time (in front of the bridge) This is where the tone suffers the most from bad pressure distribution on the bridge.
I was not able to gain a real new crown shape, but some of the S was lowered.

Then, I am ready to belive that if inner tensions are fighting themselves within the panel, tone wise, the final result is not positive (at some frequencies, or at some dynamic ranges)

biting the bullet and asking a differnt effort to the ribs, one they where not used to, may be a good idea.

Then new bridge tops may be made to installe a coherent DB...

I avoid PVA glues for ribs because of an eventual creep in time, but I was said Titebond is cristallizing well enough.