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Craig, you are amazing.

But, you need to smile for this one:

Mesmerizing skills at work here! I am just dumbfounded.

"Bump"
To keep this daunting project relevant.

More soundboard progress:

fitting, shrinkage compensation, pressing, crown development, and finaly a little french polishing to bring out the wonderful color of the aged spruce.

Caul curvatures are 2mm on short ribs to 5mm on longest.

Thank heaven for hide glue!

https://plus.google.com/photos/1054...21702478078204737?authkey=CNziyM-MoqbMTQ

50% of why I come to PW these days is to see what you post next on this fascinating project, Craig. Thank you!

Craig,
Were the ribs glued onto the sound board before, after or during the re-crown of the board?

Good Morning,
In this piano, I would have to say that the ribs are glued on both during and before the crowning takes place. We used gently dished cauls to do the gluing, so the board came out of the press with a little crown displayed. We also dried the board our beforehand,120F, such that the panel shrank about 6mm across its width. After the gluing, when the moisture returns to the panel, the crown in the long ribs develops. This happens over several days. This morning, the crown on the underside, between the longest ribs, is about 16mm. Between the two top treble ribs we have about 4mm. A good deal of this displayed crown will be lost when the rib ends are glued down to a 90 deg. shelf.

Thanks for the info Craig. And thanks for taking the time to post the photos.

Carl

Thank you indeed for posting these pictures, Mr. Hair. Having an interest in the mechanical properties of the soundboard, but not being in the business, I was very interested in seeing the cross section of the grain.

The following appears truly quarter-sawn:

https://plus.google.com/photos/1054...2558609394&oid=105412259108667869462

The following does not appear to be, should there be no illusions created by the cut or camera angles (is there?):

https://plus.google.com/photos/1054...5437176002&oid=105412259108667869462

I wonder if such mix is par for the course in soundboards.

Not being able to assume true quarter-sawn boards makes valid computation of the properties more difficult considering the anisotropic nature of wood.

Anyway, it is just fantastic and admirable restoration work, I too thank you for your postings and your information above in this thread.

Best regards-

Good evening,
Its only part illusion. the grain is far from vertical. Actually much of the wood in this board seems less than ideal. There is a lot of grain runout in the planks. One board has a curve of about 2 inches in the grain from one end to the other.

Perhapse we are just spoiled when it comes to wood selection in America. The German city-states of the 19th century were royal holdings as were the forests. Quality lumber was a closely controled commodity. You got the best that you could, used all that you could, and were probably happy just to get it.

That being said, The wood is now 140+ years old. The wood's tonal capacity more than makes up for any percieved shortcomings. And I say percieved shortcomings because the crowning capacity of the wood is still more than sufficient, as demonstrated in the photos.

It may be that our fetish for perfectly quartersawn lumber is just that: a fetish. a preferrence that is not really demanded of the enterprise.

A lot of old boards have less than quartersawn wood in them, and a lot of it seems to be used in the rear section of the board. In the back, under the plate, and so out of sight. Saving the clean stuff for where it can be seen? That would be human nature. Or it could be placed there so that the bass bridge would sit on a more compliant zone of the board.

The only board I ever saw with perfectly quartersawn wood throughout the board was from a Chickering square from the 1870s. We still have it, just for looking at.

Thanks for the kind words.

Thanks Craig, very nice looking. it is nice to take all those pics.

The wood lost by shrinkage is impressing

I do not understand whay you glue the ribs one by one, and not all at once as is it usual to ? You may need to keep the moisture very low all the time.

The relation with future cracking is clearly stated in all the litterature.

The equuilibrium between panel retractation and the force of the ribs may not be so easy to find however.

All the best

Good morning,Isaac,

Why one by one? Half the reason has to do with our use of hide glue. In the pictures you can see how the hide glue squeezes out onto the surface of the board. You can see how wet the surface gets from the clean up. We've never felt comfortable attatching another rib until the board has given that moisture up. We also like to keep the board at the working temperature. In the time it takes to glue the rib, the whole board cools, we wrap it up til everything is back to warm and dry. The other reason is that we just have'nt gotten around to it. Shameful, I know.

Future cracking. You are referring to the mortal fear of compression ridges? First, I think I must point out that all the literature is written about new wood. Old wood is qualitatively different. Rather than being weaker than new wood, it is actually a good bit stronger, particularly across the grain. Its hygroscopic movement may or may not be equal to that of new wood,( don't know, never used any), but its ability to absorb this pressure without damaging itself is greater. We just have'nt had any occurances of compression ridges. which is probably why we have had a tendancy to put maybe little too healthy a crown in the board. Too much crown has always seemed a better bet than too little, as the excess arch can be pressed out when mounting. This increases the compression in the panel and raises the impedance of the board as a whole. It also means that there will be more time before the natural shrinkage puts the panel into tension, and starts it into pulling on the ribs. In new wood, this might be a recipe for disaster. The old wood seems to take it without a problem.

Some thoughts on seasoning of wood. The whole purpose of seasoning wood is to make it stable, and its behavior predictable within a window of acceptable limits, so that it might be used as a reliable engineering material. Spruce is a conifer, and like all conifers it is a very wet wood. Both in terms of water and organic volitals. Excess water weight is easily lost to the air, this is drying, and that is all it is. Seasoning is what takes place after the water is lost. Seasoning is the stabilization of the resins in the wood, and that takes a while (seasons). In its first years, when the wood still has a lot of soft resins in it, the wood moves a great deal with the natural movement of water in and out of the cells. At the same time, the softness of the resins keep the wood's compression failure limit rather low. Consequently the wood has a strong capacity to expasnd and a weaker capacity to resist. With the seasons, the expansive tendancy lessens while the resistive potential increases. Like two lines on a graph, they converge. When the two lines meet, the wood is finally strong enough to resist its own strength. This would be the point where the wood could be safely used for predictable results. This is just traditional seasoning.

Where am I goiung with this? Well that process does not stop. It slows and slows, becomming glacial, but over a century has a cumulative effect. Accumulated shrinkage pulls the board flat or even concave. If that shrinkage is relieved, however, the panel once again has the capacity to expand and bend the ribs. And being stronger, it can do that without approaching the compressive fiber limit. I think that is why we have not had problems with compression ridges.

I agree, though, that we could probably dial back on the crown a bit. We have done some experiments with some boards from dead pianos, and it looks like we may be able to dispense with dished cauls altoghether and just press on a flat deck, go pure compression.

Be well,

Thank you very much for your answers and the interesting background, Mr. Hair.

Best regards-

Hello Craig,
A while back, you stated that you were going to try and revive the original strings. I was wondering if you have done so, and if so, did they they respond? Could you expound on the process?
Thanks,
Carl

Hi Craig,

This is one of the best restorations I've seen in a while. Thank you for taking the time to take pictures.

Your work on the original soundboard is very interesting. I'm excited to hear what this piano will sound like when its all done.

-Thanks
Kyle G.

Kyle,
thanks, we appreciate the compliment. This certainly is an interesting piano. The piano is very modern for its day, but the bass bridge is still unlike anything else I've seen. Its like three bridges in one. One thing I can say is that this is the lowest mass bass bridge Ive ever seen. The closest is the bridge-on-the-bridge construction in the Knabes from the 1890s. (In passing, those knabes also used a rib-crowned suspension with a contoured rim. Earliest I know of.)

Here are a few pictures of the bass bridge being worked on.

https://plus.google.com/u/0/photos/105412259108667869462/albums/5931301887475980705

This is hard-core piano porn. Love it.

Craig, I take it you didn't replace any of the pieces of the bass bridge, and it looks like the string grooves in the cap were sanded out. Dumb question: Does that have any effect on down bearing?

Also, what are you refinishing it with?

Jim,
Nice to hear from you.
Yes, its all the original parts.

We do sand the caps some to make a smoother surface, but I don't think there is as much material removed as it appears. Perhaps half a mm, if that.

If the board were still mounted to the rim then a mm lost in bridge height could mean a mm lost in bearing. But this board is out and already has more than sufficient crown. So I don't think there will be any problem accomodating a small dimensional change; considering also that the tennor bridge will be similarly treated.

For now the bridge just has some shellac on it to keep it clean. they will later be alcohol cleaned and french polished. The cap face is finished with a 220 one direction sanding, colored with Higgins's Black Magic(high quality india ink), then burnished with graphite with a leather covered wooden block.

Be well,

That all makes perfect sense, thanks!

Bluthner is one of the few pianos I have never had a chance to rebuild. I have not even seen one in my career!