I'm wondering what gram strength glue other builders out there are
using.
there are other traditional glues beyond hide glue, fish glue and
rabbit
glue are sometimes mentioned. fish glue is similar, but not
identical;
rabbit glue is a particular quality of hide glue.
toolsforworkingwood.com has it down pretty well. Mpst joints in
lutherie
have a small surface area and many are under some stress; strength
is not
a bad goal; but experience will tell you that a failed joint can
not be a
strong one, so use the glue that allows a joint to happen.
Joints that are 'closed', eg dovetails, mortice & tenon are where
there is
the most concern for open-time; these must be fitted tightly, but they
will swell and bind when wet by a water-based glue, takes some
experience
to judge what is a good slip-fit, and when you also have pegs to
draw it
together, maybe the glue can be omitted. Small assemblies with
critical
angles and awkward clamp setups are next (peg boxes perhaps). It
is often
worth the trouble and time to screw a frame to the bench so wedges
can be
used rather than wrestle with clamps.
What is not often mentioned is the need for deliberate and thorough
preparation before any glue up work. All tools, jigs, clamps and
supplies
should be standing close to hand. Warm water and a roll of paper
towels
(or rags) ready for spills and clean up. Put the bloody phone on the
machine. Be rude and firm with unexpected visitors, "Sorry, glue
up in
progress, cant stop now; if you must stay, would you mind putting
on that
apron and lending a hand? ..."
Prefer the strongest glue your assembly skills will allow, and
practice
dry until you are skilled at setting up the clamps and whatever is
involved. Make sure your brushes will hold enough glue to wet the
surfaces involved.
Dark backs might show a light glue just as light tops will show a dark
one; the back can be given narrow strips of contrasting dyed wood/
heavy
paper to hide that in a 'detail'; if the thin bits are soft enough
you can
improve the fit of the joint thru a gasketing effect.
* The 192 gram strength is a good general purpose glue, and
it's the
least expensive hide glue around. That's why it's the most
common.
Its real application is veneering, although you can use it for
regular gluing in a pinch. A lot of people consider it the
best
all-around glue for general woodworking (including veneering),
because it also has the longest open time. If you are new
to hide
glue, this is the grade you should get.
well, that last is not the advice I would give to a luthier.
Veneer has
its place in some instruments, the back of many necks is veneered.
Most
other joints are open and more easily assembled - veneer is often
cut from
highly figured wood, burls and other squirely wood grain will react to
water like drying wash; one must work it with an iron so that it tacks
down to the substrate, the heat smooths out the glue and trapped air.
Excess glue lubricates the surface. One works from the center
towards the
edges, and some expectation of creep must be made.
* The 315 gram strength is a special purpose glue for very high
stress applications. It is favored primarily by instrument
makers
for situations where a joint will be under constant force.
Of the
glues the 315 has the shortest open time.
So, is 192 not strong enough for lutherie, as implied by the
description of the 315?
ok for the label inside, maybe for the parchment liners, if its
already in
the pot. Ideal for the veneer on the neck.
I bought one each from them and have been experimenting. Have had
some
lamination joints fail using the high-clarity (on beech), and didnt
think
it was worth the trouble as the jointline was still easily seen.
I find 10 oz jelly jars handy to keep small premixed amounts in,
easily
labeled with marker for date and strength; keep in the fridge inside a
large zip-lock bag - but if you share that fridge, be sure all know
it is
not food (except to mold).
--
Dana Emery
To get on or off this list see list information at
http://www.cs.dartmouth.edu/~wbc/lute-admin/index.html
