Okay List, I'll bite...  Somebody asked, "Is there is a MIL SPEC for
rubber cloth?"  I can provide the following: Military Handbook 695D,
"Rubber Products Recommended Shelf Life."  You will find out that
there is more variety in rubber products than you realize.  I believe
this document is available to the public.  (You may have to buy it.)
You may also reference Mil-C-882.

There is a three-year storage life for rubber cloth (duck) sheet
products.  Of course, starting with these there is more that you may
find in terms of manufacturing standards.  A certificate of conformance
is a little out of vogue right now; and, all you really need to ask for
is the materials disclosure.  I am glad to see a few people try to use
materials engineering.

Someone talked about ozone.  Let me add that natural rubber in the
presence of photo-chemically reactive agents ("Smog" once cooked at
about 80 degrees F.) not only has ozone in it but also sulfur products.
These combustion byproducts cause the natural rubber to continue to
vulcanize.  The post manufacture vulcanization is one of the major
factors leading to early degradation.  Hence, avoid combustion
byproducts and avoid extra heat around rubber products.

I hesitate to point out that conservation or aerospace grade RTVs are
not a "silicone bathroom caulk."  They do not behave the same.  Some
can be as easy to clean up, as Paddy said.  However, I do not believe
the ones he cited are quite as reversible as promised.  No doubt, he
has developed a certain knack for the product quirks.  Nevertheless,
pay attention to the Material Safety Data Sheets and decide if you
really want to handle that particular product.

Having said that, and to those of you who are therefore inclined to
use them, I will point out that the degassing of acetic acid during the
cure causes an interesting problem: acetic acid is corrosive to lead.
The grades of RTV that Paddy listed are a little lower quality than
I would find acceptable but what I have in mind may not be easily
available to the casual buyer.  (And, my notes are not at hand, so
I have no other suggestions for you.)

Of course, casein and early PVA have much in common with each other
and are close to being reversible glue, if you understand the materials.
The more modern stuff is a very different chemistry.  The early PVA
could be removed using heat, acetone or water.  Modern PVAs, and their
derivative products, are not likely to be conservation class adhesives
or to meet your long-term expectations.  There are some conservation
class PVAs that are generally accepted in book repair and museums.
However, I do not see them in use in many musical instrument shops.

One of the potential problems with an Elmer's craft glue, fish glues
and PVA glues is the way they cure.  However, some people on this list
have most likely written articles on that topic so I will defer to
them.

Finally, I just do not understand where Paddy is coming from on his
statements about hide glue, therefore I will not spend time giving it
any credence.

In closing, I note that about 15% of all shops do true "conservation"
class work and stick to all original materials.  (I do not have handy
the reference point for that one either, sorry.)  Many of the other
shops just muddle through with whatever seems to work.

Well, I do not feel like taking part in too much of this fight,
therefore I will close with this thought.  A good chunk of what I do
is to "properly" clean up layers of the various animal, fish, PVA,
white glues, and caulks and apply the appropriate conservation class
materials in their place.  We do a lot of this work this way because
the original materials served well for fifty years and the "new and
improved" served well for twenty-five.

Wm. G. Chapman
West Point, New York