I don't mean to tempt Luis back to the keyboard with bad hand, but I've
picked up a few factoids that may clarify acrylics.
I found this on back of jar of Golden Polymer Medium (Gloss):
"Common supports (eg., cotton canvas, linen, masonite) contain
water-extractable materials that can cause discoloration in transparent
glazes. To minimize Support-Induced Discoloration (SID), seal support
with Golden GAC-100."
I believe I mentioned that I'd heard that Herr Goldin said it was the
support. Whoever wishes more info on GAC-100 (or Mr. Goldin) may call
607/847-6154, or check label at their local art supply store.
The label also says, BTW, "not intended for use as final varnish. These
mediums are non-removable." I take that to refer to rule that a final
varnish has to be removable for restoration rather than as a reflection
on qualities of the gloss itself.
Of course an acrylic company's claims are not necessarily archival
themselves (to put it mildly), but consider the following:
1. Artist's paper, formulated to be archival, does not contain these
"water-extractable materials."
2. Artists paper (except for water leaf) contains an internal size which
in any event ought to protect against such effects.
3. The use originally cited for a platinum print was not as size, as much
as "final varnish."
4. As noted, 1/12th strength is unlikely to do anything (IMHO), though
I'd like further word from the original perpetrator, whoever he was.
Permit me to add that as far as I'm concerned the devil could turn every
ab-ex painting in creation into hasty pudding & the world would be a
better place, as far too many of them consume our museum space with
acrylic sprawl, albeit quite without darkening. Although last I heard the
major conservatorial problems with ab-ex were LACK of a size (that's "a
size," note, not "size," which they assuredly do not lack), leading to
filthy pictures in acrylic. The other ab-ex problem is oil-paint-ooze --
heavily impasto'd oil paintings that have to be turned upside down at
intervals to ooze the other way.
And while we are defending acrylic, here are two other references
(though Luis's conference took place after my books were written -- as
of course did everything):
"Painting With Synthetic Media," by Russel O. Woody, Jr., Reinhold, 1965:
"Unpigmented solutions of acrylic resin form excellent protective
varnishes....The films resist all normal weathering including UV rays as
well as most chemical fumes, acids and alkalines. They do not yellow with
age and durablility, by present tests, is exceptional." That's p. 123. In
appendix, p. 150-1, he describes the tests -- usual sun, heat and
humidity.
Lawrence Jensen, "Synthetic Painting Media" (Prentice Hall, 1964) says:
"The most outstanding characteristic of the acrylic resins is their high
order of transparency; they are clearer than all but the highest grade of
optical glass. This clarity remains as long as the material survives...."
Jansen does not, as general books of this pre-Jurassic period generally
did not, cite specific tests, but in fact fairly extensive tests had been
conducted since Herr Rohm discoverd the material in the '40s.
A gallon of PURE acrylic, by the way, is probably still available from
Rohmer & Haas (Rhoplex), if you want NO additives of any kind, and at
1/12th dilution, you could varnish New York State.
Judy