Apologies for not replying sooner.

Domenico seems to have found my original post on sizing soundboards (and other things by implication) but has the following current questions. “Answers” interleaved:

> Il giorno 25/gen/2016, alle ore 18:59, Domenico Statuto <[log in to unmask]> ha scritto:

> 1. Do the sizing happen before or after the bridge, ribs etc are glued to the board?
The board is sized after the center-lines for bridges are scribed for positioning the bridges, and after it has been planed to final thickness, but before anything is glued to it. The sizing - we will leave aside the contention by me and others that it has acoustical advantages - stabilizes the wood, but it also makes it less likely that the very porous wood will absorb so much glue when bridges and ribs are glued down (and the board glued into the harpsichord as well) that the joints become “starved” of glue.

Some observations: it is VERY important, especially with pale soundboard wood, which will show, that the glue be freshly made (making size from an older batch for internal stuff is just fine), and made in a pot freshly cleaned to within an inch of its life. And the board should have been only very recently freshly planed. This is because older size might develop little dark spots of mold or mildew while the thin size cures. This has no functional issue, since spores for such things exist everywhere and cannot be avoided, but you don’t want ugly spots on your board. I like to tape kraft or other paper to my work table, and I tape down chopsticks or other little pieces of scrapwood to support the board so that I can slop the glue onto the board freely without worrying about making a mess underneath or gluing bits of paper to the board!  The observations about curling and curing in the original post still hold, of course.
> 2. Do the bridge and ribs get sized as well?
It does no harm, so I would suggest doing that. I don’t bother sizing ribs, I confess, but will often size my bridges, in part because the size acts as a minor sort of ‘finish’ which, of course, cannot compromise the glue joint, and makes the wood, once lightly polished, prettier. A slight bit of wax where the strings will touch, applied sparingly later, might prevent the spot of contact being a bit grabby or sticky on hot moist weather.

> 3. How to know the glue is properly diluted? I found a suggestion: 90% water, 10% glue; is it right?

I have a handbook of artists’ materials, Kurt Wehlte, The Materials and Techniques of Painting, which states that when painters sized wood panels before preparing them for the grounds for oilpainting, they often called for a mixture of approximately 12 parts water to one part dry glue, by volume. That’s pretty much what I always use.

Other things that come to mind: other glues don’t respond to sizing as well as does hide glue, because, to take one example, Titebond is claimed not to bond effectively to dried samples of itself. That is most certainly not the case with hide glue. Also, the film of thin size, which gives a nice “glow” to the board cosmetically, and provides a good ground for water-based soundboard painting (preventing capillary creep of the paint) will “blend” with the residue from cleaning up after gluing down the bridges, so that you don’t face issues with “staining.”

Main thing, to beat a dead horse: for a nice soundboard, the freshest, cleanest glue, pot and wood you can possibly provide.


Owen Daly Early Keyboard Instruments
557 Statesman St. NE
Salem, OR 97301

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