Alternative to xylene

I have been watching the posts in anticipation of something new and
to see when 1-methoxy-2-propanol (aka Downol PM, propylene glycol
momomethyl ether, Arcosolv PM, Downol PM. 1-methoxypropan-2-ol)
might be mentioned and what would be said about it. While one might
be able to defend this solvent as "appreciably" less hazardous than
xylene as Mr. Phenix does, I do not think it can be considered to
have "similar properties to ethanol in terms of toxicity" as argued
by Ms. Roundhill. In the U.S., both ACGIH and NIOSH give xylene and
1-methoxy-2-propanol the same TLV of 100ppm and 100ppm STEL. On the
other hand, ethanol has a TLV of 1000, 10 times that of 1-methoxy-2-
propanol (of course this will depend on what the ethanol is is
denatured with).

As for it being "a great solvent for Acryloid B-72", glycol ethers
like 1-methoxy-2- propanol, and its more infamous cousin Cellosolve,
have been highly valued in the paints, lacquer and paint stripper
industry for their ability to dissolve or swell a large variety of
materials including both fresh and aged paint films. This is
partially due to the fact that it is both a protic and aprotic
solvent.

While I am far from a chemist, some may know that Whitten and
Proctor have been involved in teaching varnish workshops for years.
We have long sought something to replace the aromatic content of our
varnish formulations for both B-72 and Laropal A-81 and therefore
have done some research on this solvent. One thing we have found is
although it has an evaporation rate very close to that of xylene, a
30% solution of Laropal A-81 dissolved in 1-methoxy-2- propanol will
take considerably longer to dry to touch than a 30% solution of
Laropal A-81 dissolved in xylene. While we haven't yet tested this
with B-72, I would suspect similar or more dramatic results.

This retarded drying time appears to happen primarily during the
diffusion phase when the solvent and varnish are combined in a
non-mobile gel. This means as a varnish, the solvent is probably in
contact with the paint for a very long time and has the potential to
fuse the varnish with the paint. I could go on more about this and
other phenomenon that cause me concern but feel the duty to cut this
post short. Suffice it to say, I would like to voice a strong word
of caution before simply substituting this solvent for any other and
particularly for dissolving resins to be used as varnishes.

Robert Proctor
Whitten and Proctor Fine Art Conservation
1236 Studewood Street
Houston, TX 77008
713-426-0191 (phone/fax)


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                  Conservation DistList Instance 25:40
                  Distributed: Saturday, March 3, 2012
                       Message Id: cdl-25-40-003
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