Hi Andrew,

I just knew the Eternal Glue Argument was about to arise again. :-)

The list archives are overflowing on this topic. But here we have from the titebond.com website (the titebond tribe being the principal enemy of the hide glue tribe):

Polyvinyl Acetate (PVA) Glue

Any glue consisting primarily of polyvinyl acetate polymer. This category includes most traditional white glues and more advanced yellow aliphatic resin glues. Although PVA glues can vary in strength, flexibility, water-resistance and sandability, they offer good performance, cleanup with water and are non-toxic. Because PVA glues tend to “creep”, or slowly stretch under long-term loads, they are not recommended for structural applications.

We are left to make of this what we will. As you say, using Titebond for laminated structural beams for buildings or building yachts is not a good idea. But experience shows that even with the stress loading of a big harpsichord, it holds together as long as you like, even in severe climates such as Australia.

Creep is not something that is readily quantifiable, since it is by definition very small and slow movements over time. It’s more of a generalised phenomenon than a numerical quantity like stress or strain.

Of course, having modern glues does not mean you can make bad joints and have the glue compensate. Titebond with correct cabinetry principles in our experience withstands long term loads just fine. Possibly the only caveat here is that I have seen tail hitchpin rails come off, but this is because from a cabinet maker’s point of view this is usually a terribly badly designed joint, hardly any surface area and very little in the way of shoulders to lock in. [From a cabinet makers point of view, a lot of the traditional joinery in harpsichords barely passes muster.] This piece can pull off with hide glue as well.

In summary, my answer to your question is that over a large number of instruments – harpsichords - over many years we only rarely observe structural failure, and even so, it may have been due to a badly done joint or starved of glue rather than all the blame being laid on creep. Others will have different answers.

I am hoping our colleague and friend here in Australia Richard Schaumloffel will soon give us the opposition case for hide glue! :-)

Andrew


On 5/03/2016, 18:13, "Harpsichords and Related Topics on behalf of Andrew Seemann" <[log in to unmask] on behalf of [log in to unmask]> wrote:

OK, now that the glue bottle has come uncorked,


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