(Pertinent bits of the emails that prompted these comments
are cited with  >  >>  etc at the end of my two screenfuls.)

Traditional glue is certainly collagen based. It's very concentrated
gelatin, made by prolonged boiling of bones, and has to be heated
to reduce its viscosity to a workable level. I think it's still used
industrially, for jobs like sticking the layers together in plywood.
The dried and hardened glue can be permanently cross-linked by 
exposure to formaldehyde gas.

In modern times the word glue is applied to all sorts of adhesives.
The impression I've been under for many years is that the white
ones like Elmer's have polyvinyl acetate as the main ingredient.
In 1983 two Finns (Jarvinen and Rinne, Acta Histochem. 72:751-752)
wrote a short paper describing the use of a polyvinyl acetate
adhesive for sections. To those of us who requested reprints
they enclosed a small green squeezy-tube with a trade name on 
it, and also some other printing which, when examined with a
microscope, turned out to be entirely in Finnish. 

(The Finns developed the micro-printing technology to accommodate
statements in a language that has very few short words. In earlier
times they could produce only large tubes of glue, toothpaste etc. 
For 2-gram tubes of Finnish eye ointment you now need an oil immersion
objective to read the instructions, but it works so well that after
finishing the treatment a X40 high-dry is sufficient.) 

The stuff that came out of the green tube looked, smelt and felt
exactly like any other general-purpose white adhesive.
I tried it a few times (the published paper was in English) but 
it was a messy technique and didn't seem to me at the time to be 
as good as chrome-gelatin. 

Patsy's Ruegg's procedure (quoted below) seems to be nothing like as
messy as the one in the 1983 Acta Histochem paper. It is important,
however, to know what's in Elmer's "glue" before using it as a 
section adhesive in research or diagnostic applications. Has anyone 
asked Elmer? Is there a publication that documents its introduction
into microtechnique? Are the products of other major manufacturers
similarly used?   Wotta lotta questions. 
----------------------------------------
John A. Kiernan
Department of Anatomy & Cell Biology
The University of Western Ontario
London,  Canada   N6A 5C1
   kiernan@uwo.ca
   http://publish.uwo.ca/~jkiernan
--------------------------------------
On Wed, 2 May 2001, Abizar Lakdawalla wrote:
> I was under the impression that Elmer's white glue was collagen based!
> 
> Patsy.Ruegg@UCHSC.edu had written:
> 
> > A good way to keep sections on the slides if you are not doing collagen
> > markers (the glue interfers with staining) is to precoat the slides (reg.
> > Slides) with a solution of 5% elmers type glue in water, dip the slides in
> > this then let them air dry. ...
> > ... but beware that glue is collagen based and will cause problems
> > with some IHC markers.
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