[pianotech] Glue for hammers - question

[Ron Nossaman]

André Oorebeek wrote:
> 
> Chuck, this glue is not for sale in a shop.
> It was developed on the side for me.
> Tomorrow I will try to contact that factory and ask them what kind of 
> glue it actually is.

So it's not an off the shelf commercial product. That's pretty 
much the answer.

Meanwhile, to everyone:
More and more people are saying that they use Titebond molding 
and trim for hanging hammers, yet I still hear repeatedly how 
critical to good tone a hard glue is for hammer hanging. 
Titebond M&T, folks, isn't a hard glue. It's considerably more 
flexible after curing than original Titebond. Who's wrong?

I've done a little grant-free testing of my own of various 
glues for various working properties. One of the latest was on 
how hard the glues I use are, relative to one another. I've 
looked, and this is one of the properties virtually never 
listed in glue specifications ANYWHERE. I recently acquired 
some Franklin Assembly 65 from Wessell Nickel & Gross, which 
looks like fine stuff, which I included with Titebond M&T, and 
Original Titebond in a simple flexibility test.

I smeared a track of each glue, roughly 60mm long, about a 
millimeter thick at one end, graduated to nothing at the 
other. After about five months cure time (hope I didn't rush 
it unnecessarily) Here's what I find.

The  Titebond M&T is quite flexible, and will only break when 
bent sharply and quite suddenly. It's sort of a shear 
thickening fluid, like Silly Putty, or a cornstarch and water 
mix. If hammer tone is critically dependent on the rigidity of 
the glue joint, this is clearly not a good choice (unless it 
doesn't). Original Titebond is much less flexible, and breaks 
with a much less sharp, and slower bend. But it still has some 
inherent plasticity. The Franklin Assembly 65 is brittle, 
exhibiting little if any plasticity. It's more resist to 
bending than Original Titebond, and breaks when bent.

Of the three, the Assy65 looks to be the superior hammer glue.

I, personally, use hot hide glue. It:
1: Doesn't smell objectionably unless it's gone sour as a 
result of mismanagement.
2: Is harder and more rigid than Assy65
3: Is quick in use, and easy to handle
4: Has no shelf life in crystalline state. I'm currently using 
the last pound of a 100lb bag I split with someone 30+ years 
ago. It's still as great a glue as it ever was.
5: Doesn't string all over the place unless you're using the 
wrong grade, and/or haven't mixed and heated it properly. It's 
something you need to learn something about to use comfortably.

More about hot hide glue, since this part has never been 
discussed here to my recollection.

Hide glue comes in different gram strengths. In practical 
terms, it's a measure of the ultimate strength and gel rate of 
the glue. Most people start with too high a gram strength and 
shoot themselves in the foot. Those who say they found hot 
hide to be unmanageable usually bought it from Schaff. Theirs 
is 370-399 gram, which I consider to be impossible for general 
use. Pianotek sells a 251 gram weight, which is manageable, 
but still touchy for general work. I prefer 192 gram. It's a 
balancing act between thickness and gel time. For hammers, 
particularly, you want a fairly thick glue that won't 
"string", and will still gel before it runs down into the 
hammer tail cove.  The high gram weights are super critical of 
water content for this use. Thin enough to not string means 
too thin to gel in time to not sag. The 251g has a wide enough 
operating range, and is quite usable for hammer hanging since 
you can get a quick gel and  minimum sag with a mix that's not 
too thick to use. I find it too much for player and felt work 
though. Add enough water to make it usable covering 
pneumatics, and the initial tack isn't good enough to let you 
move on without standing around holding things and waiting for 
the glue to grab. The 192g is good enough for hammer hanging, 
and much better for player and felt work. It can be mixed 
thick enough for hammers, with a gel time that works, without 
stringing glue, and thin enough for player and felt work 
without losing the initial tack that lets you get on with it.

Dries brittle, scrapes easily, softens with heat and moisture. 
That, everyone already knows.

And no, I don't use urea. I bought some to play with, but 
haven't need to yet.

Ron N