RE: SAFE URETHANE OR VARNISH?

DEAR MICHAEL,
        Thanks! I will look into your suggestions!
                                        CHEERS!
                                                        BOB

-----Original Message-----
From: msb@f32.usask.ca [mailto:msb@f32.usask.ca]On Behalf Of Michael
Briggs
Sent: Thursday, March 03, 2005 5:42 AM
To: alt-photo-process-l@sask.usask.ca
Subject: Re: SAFE URETHANE OR VARNISH?

On 02-Mar-2005 Bob Kiss wrote:
> DEAR LIST,
> This may sound off topic but not far. I just got two great wood flat
> files in which I hope to keep my alt prints and 100% cotton papers. They
> are made of plywood. What worries me is that I know I shouldn't put
prints
> or papers near raw plywood inside the drawers. I am hoping that I can
seal
> them with a urethane or other varnish to provide a barrier between the
acids
> and lignin in the plywood and the prints/papers.
> Please suggest which type of varnish is best (archival?) for this
> purpose.

I am not an expert of this. From my reading, paint, especially fresh, emits
fumes that are bad for silver-based photographic materials. Fresh paint can
damage photos in a few days. Hydrogen peroxide is emitted for at least
weeks.
Painting your wood files could make the situation worse. Baked enamel on
steel
is considered the best because of low emission of fumes.

The Kodak publication "Conservation of Photographs" reports (p. 84) that
latex
(water based) paints are much better than alkyd (old based) paints. The
research seems to be from circa 1952, so the materials may have changed
since
then. I _speculate_ that if you want a clear varnish, the newer so-called
water
based clear finishes might be better than the older urethane varnishes. The
technology has some similarities to latex paint. I say so-called, because
while water is the main solvent, other petroleum-based solvents are used.

Another clearish finish that _might_ be good is shellac. Shellac is made
from
an excretion from insects that is dissolved in alcohol (ethanol). The best
shellac is made by mixing fresh solid shellac flakes with ethanol, rather
than
buying pre-mixed. I don't know of any studies of the effects of shellac on
phtographs.

I suggest further research. If you decide use a finish, let it air out for
at
least one month.

--Michael
Received on Thu Mar 3 07:17:12 2005