[Tom Edgerton]

Pam, I also like the 50-50 mix with Soluvar.

Straight matte varnish was the preference in the mid 20th Century because it emphasized "flatness" of surface, and seemed more "contemporary." For portraits though, I think it kills depth and transparency in shadows. Also, if not carefully applied, matte varnish can impart a streaky look to darks. The half-and-half mixture to me avoids some of these problems, without giving the work such a high gloss that it's hard to view through the glare. It still evens out the dull and shiny areas of the surface, and pops up the color, just like straight gloss varnish.

I don't know that matte varnish is any less archival than gloss--it probably is somewhat softer as Steven notes--but one needs to exercise some care in applying either--the most important consideration is to avoid an excessively humid environment when applying. Also, once it's applied, leave it alone and don't brush it once it starts to set up, especially if there is matte varnish in the mixture.