Tightbond Creep

[Farrell]

John, what are your feelings regarding cold hide glue. My understanding is that it has all the strength properties of hot hide glue, although I realize there is some controversy over that. Thanks for the panel pictures.

Terry Farrell
  
----- Original Message ----- 
[link redacted at request of site owner - Jul 25, 2015]
To: "Pianotech" <pianotech@ptg.org>
Sent: Sunday, April 27, 2003 6:54 PM
Subject: Re: Tightbond Creep


> Ron Nossaman wrote:
> > 
> >> You will also find the same information in "Understanding Wood" and 
> >> the "wood Handbook".
> > 
> > 
> > I don't find it in Understanding Wood. Must be looking in the wrong 
> > place. I did find mention of "tends to yield under continued stress" in 
> > the Wood Handbook, with no differentiation made between white and yellow 
> > PVA. There is a considerable and obvious difference between the two, as 
> > anyone familiar with both knows. It also mentions crosslinkable PVA, 
> > which would be the Titebond II equivalents, with no mention of creep 
> > whatsoever.
> > 
> > I'd still like to find some real information on this for my own 
> > education, if nothing else, should anyone happen across it somewhere.
> > 
> > Ron N
> > 
> 
> 
> Ron,
> 
> I know you will not finds this in the least conclusive but if you get 
> your hands on Technical Bulletin No. 1512 you will find a few charts. On 
> page 73 there it a chart of side to side joints with various glues. The 
> samples are subjected to repeating cycles of 65-30 and 90-30 RH. The PVA 
> glue start out fine but after 36 months it slip in both cases. It is at 
> the bottom of the list in the 90-30 RH test after only 12 months. Hide 
> glue is near the top of the list in both tests.
> 
>  From page 23
> "Probable the most serious limitation in the use of these adhesives 
> (PVA)in woodworking is the lack of resistance to continuously applied 
> loads."
> 
> I would relate some personal experience but that would mean nothing to 
> you. One thing seems clear at least to me: PVA is not a structural 
> adhesive because of its cold flow. It never truly hardens like many 
> other woodworking glues - urea resin, resorcinol, phenol-resorcinol to 
> name a few. Hide glue is only kept off the list of structural adhesives 
> because is is not water resistant - in every other way it meets the 
> criteria.
> 
> John Hartman RPT
> 
> John Hartman Pianos
[link redacted at request of site owner - Jul 25, 2015]
> Rebuilding Steinway and Mason & Hamlin
> Grand Pianos Since 1979
> 
> Piano Technicians Journal
> Journal Illustrator/Contributing Editor
[link redacted at request of site owner - Jul 25, 2015]
> 
> 
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