Painters used to use mastic, a softer varnish that is more prone to bloom, a white discoloration caused by humidity, mastics use is now limited to the making of mediums. Copal varnish, usually made from now scarce fossil amber has become rare and in any event formed a brittle film prone to cracking. Today copal is mostly replaced by synthetic resins like alkyd. I learned to paint with Taubes copal medium and used to love it, the formula has changed and it is no longer made with genuine copal. There are new and expensive final picture varnishes. I don't use them.
Dammar is the standard artists varnish today, it is a resin from a number of different trees found in the far east, mixed with turpentine to make it liquid. Dammar is the only varnish in my studio. I either buy a liter bottle from Winsor Newton or I buy it from Utrecht. Utrecht will sell you dammar tears in a cloth bag closed up in a quart can. You open the can, pull out the bag, fill the can with turpentine ( remember dammar thins with turpentine, mineral spirits won't do) drop the bag back in, retaining the end of the string that trails from the bag. Just like making tea. If you buy those little tiny bottles at the art store you will pay many times as much as if you buy it in quantity. The markup on those little bottles is astronomical. Sometimes I also stock a can or two of spray varnish in a can. They have a crazy markup too, but they are convenient.
Matt varnish is an abomination before God! Here's why. Lets look at the pictures in magazines for a moment, if you look at American Art Review, The American Magazine of Antiques, Fine Arts Connoisseur, American Art Collector (some of these magazines have been friends and supporters to me over the years so I try to list them all, ) or other high end magazine where top quality reproduction is important. They use a coated paper. Its shiny. That means that a lot of the light hitting the ink on that page is returned to your eye, giving you...brilliant color. Tabloids from the grocery store, or what we once called pulp publications are printed on cheap paper that has a matt finish, like newsprint. It returns less of the light that hits it to your eye and the result is dull color. When you put varnish on a painting one of the things you are doing is making the surface shiny like it was when it was wet. It returns more light to the viewers eye.......and you get the idea. Matt varnish robs your colors of their brilliance by interfering with the return of the light to your eye, So matt varnish absolutely KILLS your color. Also matt varnish is usually made by adding wax to the formula, which weakens its protective film as well.
When a painting dries, sometimes the oil drops down into the substrate particularly in the darks, and areas of the painting go matt. This is called drying in. Restoring the shine to these areas is done with a can of spray retouching varnish. At least these days. In the next post I will tell you how the old guys did it. I will return tomorrow with a blog about how they sprayed varnish in the 19th century and how you can do it yourself, saving a little money and amazing your friends with a bit of cool and nearly forgotten technology.
My wife is telling me I need to break these posts up into smaller pieces, she says blog readers won't read long entries. I will try to comply.