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John, "Maroger's Medium" is the combination of "black oil", which is linseed oil cooked with litharge to saturation, and a saturated "cut" of mastic tears (the resin of the pistacio tree) in turpentine. The mixture forms a thixotropic gel, which becomes fluid with manipulation and sets up as a gel when undisturbed. Jacques Maroger was the head conservator at the Louve for a number of years through the 1940's, and this medium is the result of years of experimentation on his part . He called it "Rubens' Medium" as he believed he had re-created a "secret" of this old master, which had been a "holy grail" alluded to by DeMayrne, who presumed to document Rubens' studio practises duing his lifetime, and sought after by no less than Joshua Reynolds, whose experimentations resulted in a number of forumlae generally employing water-soluble gums (e.g., gum arabic, gum tragacanth) to effect a jelly-like consistency. These were used quite widely through the 18th and 19th century, were known generically as "Meguilp" (which can be found spelled about a hundred (?) different ways) and equally well-known to be the root cause of a wide range of paint failures.
Maroger's is the favorite medium to hate among painters who feel the cause of all manner of paint failures is the use of resins and treated oils of any type, and detrimental to archival permanence.
Shooting from the hip (always a bad idea) I believe Soluvar, like Gamvar, is an isoacrylate resin, and if so, as Marvin advises, it would be bad practise to apply it as a final varnish to a painting that is not thoroughly dry. I'm off to see if I can learn what kind of material Soluvar actually is.
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