Hello All
A thread on hide glue?
Can we all imagine what "average" people must think of us debating with such
passions -
the benefits of hot animal parts?
Its wonderful...
I recommend of course , the lute courses by David Van Edwards . He included
therein a GREAT discourse on hide glue .
With regards to hide glue - its strength and resultant grading, I had a
most enlightening conversation once with
Eugene Thordahl, he of Bjorn Industries- who is widely regarded as an
expert in all such matters.
Yes he said, we grade and test all hide glue and indicate the strength for
the prospective client.
Hide glues are in fact sold in gram weights which correspond to the tested
strength of the product.
He recommended 180 gram for most all instrument building, and perhaps for
bridges a higher gram strength .
He also indicated that if one mixed 180 with 315 in equal percentages one
would get a gram strength roughly half way between the two.
He also indicated that the higher the gram strength the lower the working
time. You really need to rehearse to use 315. There is little if any time
for errors to be
corrected by wiggling around the piece or you will introduce a weak joint.
Also he told me that Hide glue is remarkably forgiving, has if mixed a
shortish shelf life even when kept in the fridge BUT an indefinitely long
shelf life if left in its native crystalline state.
At Bjorn he has done MANY comparative experiments testing strength of joints
with hide glues in which the glue has sat around, been reheated etc and as
well
been heated to 160f as opposed a more nominal 140f and that for various
lengths of time. You might consider giving Eugene a call on these topics, he
has both facts and figures..
After I complemented him on his enviable knowledge of the subject, he
replied ,dryly,
"Well Richard, when you've been around the glue pot as long as I have,
something is bound to stick....."
Yes rework is not just easier, its actually possible when using hide glue.
I myself just finished restoring a sweet German Harp guitar by Haberman for
John Schneiderman out here on the west cost USA.
On that instrument someone actually tried to generate a repair using the
equivalent of Titebond.
It took me over a week of solid work to undo the mess where if hide glue
had been used it could have been done in less than 1/2 day. It is MORE than
likely that the use of other glues as opposed to hide glue could in fact
make rework close to impossible. Imagine replacing a worn fingerboard on a
baroque guitar or 13 course lute if it had been adhered with Titebond 3!!
.But there is another reason I prefer hide glue, and its one not usually
discussed.
Try to obtain or create as Keith Johnson of Reference Records did in
developing some loudspeakers some time ago, a tiny stethoscope. He did this
so he could listen to the smallest of sounds generated in very specific
places on a loudspeaker when excited with energy.
He listened to the spider, the surround in various places as well as the
cone itself near the center and outwards to the edges. As well he listened
to the sound of the "basket" the metal frame of the speaker.
You would be amazed to know that the "sound" as generated by a loudspeaker
is not just what comes from the speakers cone itself, but is an amalgam of
all these sounds I have described as generated by every part of the speaker
one added to the other. It is interesting to note that some of these
contributed sounds were in excess of 20percent pure distortion!.
The surrounds in particular are a problem with all dynamic loudspeakers - as
opposed to electrostatic types like the Quads. This was the reason Keith did
not like multiple arrays of small long throw drivers - the distortion
effects of the surrounds were too distracting to him.
Like wise on a musical instrument, every part has its sonic contribution to
make.
In the guitar world there are those makers who can CLEARLY distinguish
between the sound a rosewood or ebony fingerboard imparts to an instrument.
Here the adhesives used will unquestionably effect the sonic behavior of all
the constituent parts .
If the adhesive is too soft , creeps in any way , or is rubbery at the
joint - NO MATTER HOW STRONG - it will terminate the materials involved in
a manner equivalent to what one would expect in using constrained layer
damping. Constrained layer damping is used to deaden resonance's - not
transmit them. If the adhesive becomes too brittle (and cyanoacrylate does
this) NO MATTER HOW STRONG, it will most likely act as a boundary and
reflect back energy into the materials involved on either side of the glue
joint..
I don't believe we want these sorts of behaviors in our instruments
anywhere , as everything - neck fingerboard pegbox staves etc as they are
"connected" together with adhesive, act upon one another and thereby
contribute to the sonic behavior of the instrument as a whole.
Now hide glue during MOST of its life transmits sound pretty darn
transparently .. This will couple the soundboard for instance tightly to the
braces, j bars etc as glued underneath over the entire audio spectrum so
that the top can develop a wonderful resonant sound from PPP to FFF.
How many of us have noticed that upon first stringing up an instrument in
the white (and that JUST after the top and fingerboard have been attached) ,
that on top of being a bit tight sounding it can be also a bit dull as
well and can be a little out of balance too?.
Yet with only several days of time under its belt said instrument begins to
open up.. Usually we think that the "top is breaking in" and while in my
opinion I believe this is to be true I also believe that a strong
contributing factor in these first several days is that the hide glue used
in the last operations of building the instrument -most likely in the
adhering of the top to the bowl- is becoming stiff enough to allow the
transmission of the finer and more subtle harmonics throughout the
instrument. With the tops of course an additional set of months is going to
be required for the instrument to really attain its bloom.
I believe that all the plans we use from these ancient genius'such as Laux
Mahler , Christian Hoffman , Tielke , etc and all their bracing schemes and
dimensions are BASED around the use of Hide Glue with the knowledge gained
over centuries as to its behavior.
None the less, I don't disagree with those who disdain its use. After all
Robert Lundberg sought to use (or so it would appear) other glues whenever
possible- but that we are now entering terra incognita with respect to what
such instruments are likely to do sonically as a result....
Richard Lees
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