[ Re: "Cabinet Maker Hates Hot Glue", 000822 MMD ]

Yesterday Mr. Herr made some very interesting points about hot glue.
I use it exclusively where it is appropriate in rebuilding, but I can
see the old gentleman's point of view.  It is very hard to use for the
large joints in cabinet making, and modern adhesives with their long
'open time' have pretty much taken over.  MMDer John Nolte, a pipe
maker, uses yellow glue for his wood pipes, and there is nothing wrong
with that, as long as the joint doesn't have to be taken apart for any
future rebuilding.

But modern technology has come to the rescue, for some furniture
makers.  When I was in high school, we took a tour through the
Kittinger Furniture factory in Buffalo.  They made very high quality
furniture, according to traditional methods.  Hot glue was used for all
the joints, but of course, many of the joints were imperfect, since it
was impossible for the hot glue to fully wet the larger surfaces while
still in the liquid phase, before it cooled down.

They had a rig, whose function I didn't understand then, but is clear
to me now.  After the piece was assembled, it was moved on a conveyor
through a shielded archway into an apparently home-made device
assembled from war-surplus radar drivers -- sort of a giant microwave
oven with open ends.

It seems that hot glue is a thixotrope; that is, when it is in the jell
phase, application of energy (mechanical or thermal) will temporarily
reliquify it.  This virtue is used in hammer veneering; see Don Teach's
article about this in MMD 1999/12/14.  As the furniture passed through
the high frequency RF field, the resultant molecular agitation of the
glue-water jell, the same thing that makes the food hot in the
microwave, reliquified each bit of the glue in turn.  The result was
completely and perfectly wetted hot glue joints, that drew up tight
and sound, and will last forever.

Richard Vance

 [ At http://www.m-w.com/cgi-bin/dictionary only "thixotropy" is
 [ listed: "The property of various gels of becoming fluid when
 [ disturbed (as by shaking)."
 [
 [ The Uhu adhesive company of Germany contributed this definition
 [ of thixotropic glues to the "Do It Yourself Lexikon" at
 [
http://www.bau-markt.de/sidm/heimwerker-lexikon/uhu_thixotrope_klebestoffe.htm
 [ (translated from German):
 [
 [ "Thixotrope glues
 [
 [ "Thixotrope adjusted glues change, through agitating or vibrating,
 [ from a relatively pasty state into a liquid state, and allow
 [ themselves to spread agreeably.  Then, in a state of rest, they
 [ assume again the original viscosity.  Thixot rope glues are thus
 [ not to be confused with gel-like adhesives which don't change state
 [ through movement."
 [
 [ I guess that applied heat would have a similar effect.
 [
 [ See the Kittinger web site at http://www.kittingerfurniture.com/
 [
 [ -- Robbie