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MMD > Archives > November 1996 > 1996.11.03 > 03Prev  Next

Soundboard Cracks
By Craig Brougher

Jon Page luckily corrected a slightly misguided piano shopper in regard to finding a good player piano, and I certainly agree with him. Soundboard flaws are easy to fix, and the only thing you need to worry about are sympathetic buzzes caused by loose ribs.

If you are fixing just a few of these in an old upright and can't seem to get to them behind the supports, Sherwin Williams sells a clear epoxy that sets as hard as hot hide glue will. Make you some thin wedges or use putty knives as spreaders, and a length of furnace tape that can be slipped behind the support posts and used to seal under each hidden part of the loose rib (so the epoxy won't run out and down the board). Now, using something like a piece of flashing bent at a right angle like a thin, flexible piece of "angle iron" pour the epoxy into it and let it run down into the crack. Pull out the putty knives, wipe off the glue that squeezed out with a lacquer thinner rag, peel off the tape and clean under it by pushing the rag through with a stick, and you're done.

If you have a lot to fix, don't do your fixing first between supports and then try to get behind them. Start at the top rib and fix it all the way down. Then take the next rib underneath that one and go all the way diagonally across the piano, and so forth.

Now this is very important! In 99% of the cases in which the soundboard has dried out, the bass bridge joint is actually broken and is held on mainly by its three screws through the soundboard. In more cases than not, this causes an upright piano to sound very "tubby" and the bass has added to it a "thump" sound (to a sensitive ear, that is). Also, the piano will never have a bright, crisp, clear tone anywhere in it because the development of timbre relies on the bass strings and their sensitivity to resonate with the other strings in the piano (that's why the call the bass section the "foundation"). You have to take the bass bridge and cantilever off the soundboard, fix it all up, and replace it, and sometimes that is hard to do because of inaccessible screws, but you'll figure it out!

In one piano, I drilled a 3/8" dia hole through a back support in order to get to a screw head, then after replacing the bridge and screwing everything back tight again, I doweled the hole, using hot hide glue for everything.

Just a final note about soundboard glue: Never use carpenter glues for soundboard work. They are elastic, which means their joints creep over time and they do not conduct sound very well at all, deadening a soundboard, they dry by water evaporation first, which means they will never be strong in a situation where they cannot be clamped, and worst of all, they cannot be removed (to my knowledge) and fixed right. They are the worst kind of glue that man has ever come up with for piano work. I cannot think of a time when I would ever, in my wildest nightmare, use yellow carpenter glues. They don't even repair chairs very well! (I figure they are for carpenters to stick things up long enough to allow them to get out of the house, when they just can't figure any other way to do it. Do you suppose?).

Any glue that is elastic and relies strictly on a mechanical bond with wood (like carpenter glues) cannot take even a little continual tension without eventually breaking, because the constant tension keeps stretching it each day just a little until finally you can see the joint. And nothing likes to test a joint's mettle better than a large expanse of wood! Not to mention little things like chair rungs, etc. And the bad thing is, once applied, you cannot rectify the mistake later. You ruined it! So please, please! Do not get out your bottle of carpenter glue with the handy spout and begin squirting. Somebody one day might actually like to have heard that piano sound the way it did when it came from the factory, and after you've ruined it, they will never again hear its tones as it could have produced. Use hot hide glue primarily for everything you can. It produces a chemical (and mechanical) bond with wood and dries hard. It is re-fixable, it is invisible, it is stronger in wood than carpenter glue, and it conducts sound perfectly-- all frequencies and effects, and when used correctly will last for generations, not "probably ten years."

Craig B.

(Message sent Sun 3 Nov 1996, 13:54:23 GMT, from time zone GMT.)

Key Words in Subject:  Cracks, Soundboard

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