> From: Stephen Birkett <birketts@wright.aps.uoguelph.ca> > Subject: Re: hide glue "tradition" > To: pianotech@ptg.org > Date: Tue, 19 Aug 1997 02:23:28 -0500 (EDT) > Reply-to: pianotech@ptg.org I size my key bushings before rebushing. Would you also size hammers and shanks before hanging them? David ilvedson, RPT Pacifica, CA > > Please elaborate - how DID the old guys do it??? > > > Three things: > 1. Tooth all glued surfaces > 2. Size everything > 3. Use ultra-thin glue. Make thin glue, thin it until it looks like it > wouldn't glue anything, then add more water. Then it's thin enough. > > Why? > Toothing improves the bond and allows the extra glue somewhere to go when > you clamp the joint. Thin glue is very easy to expel from the joint and > requires less clamping pressue consequently. (After all that's why we > clamp.) Old toothing planes are lurking everywhere...they weren't just > used on veneers. In any case you only have to look to see toothed > surfaces everywhere. > > Sizing prepares the wood and makes it behave. Unsized wood will suck out > the water from the glue almost as soon as you put it on, thus requiring > pre-heating as a last-ditch effort to make things last long enough to get > the clamps on. Thin glue can only be used on sized surfaces. Evidence for > sizing is clear on almost any old artifact, piano, organ, furniture etc. > Sizing was often done en masse. The old organ builders sized more wood > than a railway trestle bridge needs. > > Evidence for thin glue is clear on old pianos...you can see the long thin > runs that have been expelled from the joints. Glue that is the thickness > we are "supposed to" use nowadays does not flow in this manner. The runs > are so precise and long that you can even use them to analyse how a piano > case like a Graf was assembled. > > By the way there is such a thing as "bad" glue...and there seems to be a > lot of it floating about on this continent. Take care. Also never heat > hide glue over 60C or it is impaired (see Wolfenden on hide glue)...in > fact any temp. below 60C that the glue is liquid is acceptable. The old > guys didn't use thermometers. > > You can't tell by looking at broken down pianos whether the surfaces were > pre-heated. But there is clear visible evidence for the above three > points. And experience shows that the method works with no heating. > Heating every piee to glue is a royal pain in the butt, so you can bet the > old guys would not have pre-heated. They weren't stupid. > > [No claim to having discovered the method above...credit is due to my > colleague Bill Jurgensen, an ex-patriot US organ, harpischord, piano, > violin maker who lives in Germany. Evidence on organ cases and pipes is > even more obvious than in pianos. There isn't much harder to glue than a > windchest on a cathedral organ...no pre-heat needed.] > > Stephen > > Stephen Birkett Fortepianos > Authentic Reproductions of 18th and 19th Century Pianos > 464 Winchester Drive > Waterloo, Ontario > Canada N2T 1K5 > tel: 519-885-2228 > email: birketts@wright.aps.uoguelph.ca > > >
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