Bill when you mix up your medium do you make just a little bit just for the day, or do you mix up a big batch in a bottle or a jar. I really am going to do this. I would prefer to mix up a big bunch but if it gets thick or a skin or something I won't do that.
Also do you use this to seal the painting after it dries?
I mix up an ounce or two, of my medium, and I store it in an empty, discarded, medium jar, with an airtight lid. It keeps for a very long time, and when I find it getting low in the jar, I mix some more, and just pour it in on top of the remaining medium in the jar.
I buy a bunch of those little plastic medicine cups from the drug store--the kind that have a dozen "increments" on the side.....mg, oz, drams, teaspoons, etc., etc.
I use "drams to measure my ingredients. I pour 2 drams of Linseed Oil into the cup. Then I pour another 2 drams of Walnut Oil into the cup, bringing it up to 4 drams. Then I scoop out some of the very thick, viscous, Venice Turpentine with a palette knife, and place that into the measuring cup. After a time or two, it is very easy to estimate how much is required to bring the final measurement up to 6 drams. (That represents 1 portion of Linseed, 1 portion of Walnut, and 1 portion of Venice Turpentine.)
I mix these ingredients while they are in the medicine cup, stirring it with my palette knife (the one with the Venice Turpentine clinging to it). When it is thoroughly mixed, I pour this into my "reservoir" container (the discarded medium jar). Then, I pour enough Oil Of Spike into my measuring cup to make 4 drams (this represents 2 portions of Oil of Spike).
I stir this, around, basically for the purpose of cleaning the resin off my knife, and rinsing the measuring cup. Then, I pour this into my reservoir jar.
I cap it up, and shake it until it represents a homogenous mixture, with no striations being evident.
This is my painting medium. To use it, I pour about a half teaspoon of it into my medium cup clipped to my palette.
It is smooth in its flow, it is relatively non-toxic, it is slow-drying on the palette, yet it dries usually within one, or two days once applied to the canvas, it smells absolutely wonderful, and it is rather expensive. However, you only use a bare minimum of it when painting, so the cost gets rather "spread out" over several paintings.
Be careful.....there are some "imitation" versions of Venice Turpentine, with Shiva being one with which I am familiar. That stuff is NOT real, bona-fide, Venice Turpentine. Venice Turpentine is the unadulterated sap of a Larch Tree. The real stuff has a rather pleasant, "fruity" smell. It should NOT smell like Distilled Spirits of Gum Turpentine.
I purchase mine from a U. S. outlet of the Zecchi Art Company, in Florence, Italy. Jim and Jody Wahab, at Baden Treehouse in N. Carolina handles the Venice Turpentine.
It is not a good idea to use this, or ANY "painting medium" as a "final varnish". Final varnishes need to be removable, and must not bond, or cross-link with the surface of the painting under which it is being applied [as this medium will]. The reason is that all final varnishes yellow with age, and after many years, you want your varnish to be removable, and not become bonded with the surface of the painting. Mediums should be used within the painting; varnishes should be applied over the painting.