Yesterday I read and re-read all the recent discussions about the
theory and practice of hide glue in piano and player construction,
including all of Craig Brougher's articles.  It fascinates me that
animal glue -- hide glue -- is still the best adhesive known for
sounding boards, as in the piano and violin, and it is also marvelous
when periodic repairs are expected.

Hoping to learn more about the physical chemistry of this adhesive
I wrote to our members Frank Himpsl and Jack Hardman (both chemists):

> I don't expect you to be an expert in the arena of glue, but I don't
> know many expert chemists.  Besides, a piano-loving chemist (of
> practically any specialty) is best for this challenge!  Could you
> provide some answers to these knotty questions?
>
> 1. What is the nature of the bond between hide glue and wood?
>    Is it a chemical bond?  A mechanical bond?  How does one
>    measure the quality of the bond?
>
> 2. What's the effect of the water content?
>
> 3. Is there a better "thinner" than water?
>
> 4. Which molecules in the hide glue do the work?  Make the smell?!
>
> 5. What "Incoming Quality Inspection" can a piano tech make to
>    assure that he receives good quality hide glue?
>
> 6. What extra refining could the piano tech do (in case he can't
>   get the "good stuff" every time)?
>
> Could you write a letter for publication on this subject?
>

My thanks to Frank Himpsl and Jack Hardman for their replies, which
appear below (slightly edited).

Robbie Rhodes