Robert Gamblin markets Neo-Meglip as a non-toxic substitute for Maroger's medium. The promotional information for Neo-Meglip claims that the working properties of the medium are similar to those of meglip.
Although the term meglip is used throughout the history of oil painting, very little is known for certainty about it. Even though Jacque Maroger claimed to have rediscovered six oil painting formulas used by the "Old Masters", only one has come to be known as "Maroger's medium", a mixture of litharge (linseed oil boiled in lead) and mastic resin. This mixture results in a silky gel that flows easily, yet "holds the stroke", meaning that paint that has already been applied remains undisturbed when overlaid by additional brush strokes. Although Maroger did not himself call this gel medium meglip, everyone today does.
Neo-Meglip has many desirable qualities for oil painter's seeking to replicate the effects of "Old Master" paintings. Maroger's medium (real meglip) and Neo-Meglip are indeed similar, but only to a point. My intention here is to outline methods for exploiting the unique properties of Neo-Meglip and not to compare it with real meglip. My experience with meglip comes from working with the two-part formula available from Studio Products, which can be purchased HERE. A good analysis of meglip's history and discussion of its archival permanence can be found HERE.
Neo-Meglip is formulated from an alkyd resin. Unfortunately, the actual formula, like all alkyd resin products, is a trade secret of Gamblin Artists Colors. My guess is that it is a mixture of alkyd resin, poppy seed oil (to extend working time), and mineral spirits (the evaporation of which would cause the medium to stiffen). But that's pure speculation on my part.
Many artists stay away from products of uncertain composition and I am also generally skeptical about proprietary art materials. That said, the Gamblin product lines demonstrate a clear concern for conservation issues. While in Portland, I made a point to tour the Gamblin facilities and briefly discussed oil painting materials and techniques with Mr. Gamblin. I was impressed by his informed understanding of oil painting techniques. Nevertheless, I followed up with the Director of Conservation at the National Gallery. He expressed confidence that modern alkyd products, such as Neo-Meglip,will not cause "inherent vice", material defects affecting longevity or aesthetic durability. Paintings made with Neo-Meglip dry to a tough gloss finish. Paintings I've made over two years ago using Neo-Meglip are as fresh and crisp as they were at the time of their completion with no signs of distress.
Neo-Meglip has a longer working time than more fluid alkyd mediums, like Galkyd. Otherwise, it dries similarly to regular alkyds, becoming increasingly stiff and tacky. Like other oil mediums, Neo-Meglip dries from the top down. A thick glob will form a flexible bubble over a soft interior. Unlike real meglip which becomes less viscous with mechanical action (like blending), once stiff, Neo-Meglip remains stiff and will not return to a more fluid state without thinning. Neo-Melgip acts like a fast drying version of a stand oil medium(2 parts stand oil to 1 part OMS).
The time it takes to change from viscous gel, to stiff paste, to hard surface varies greatly depending on the pigment and the grinding medium. Raw Umber, for example, dries fast because of its magnesium content and gets stiff early. About an hour after its application, you can float a second layer over a layer of Raw Umber easily. In general, earth tones are stiff in one to two hours. Most other colors are stiff in two to three hours; however, some colors, such as Gamblin's Radiant White (titanium white ground in poppy oil)take much longer.
After about twelve hours the earth colors will have have set-up as a flexible membrane. The painting's top surface will be completely dry in four to six days.
If Neo-Melip sits unused for a sufficient length of time, it will begin to separate. Shaking the bottle will restore the homogeneity of the product before use. After breaking the seal of a bottle, Neo-Meglip should be used quickly; it can dry inside the bottle if their is enough air. After opening, I like to remove the product from the bottle and store it in pint-sized metal cans (available from The Container Store).
Alla primera literally means 'from the start' and refers to starting and finishing a painting in one sitting. Wet-into-wet refers to the practice of painting over the wet paint of earlier layers. Only an extraordinarily skilled painted can produce a crisp image and wide tonal range in a single sitting. Luminous effects are more readily achieved from multiple transparent layers painted over a series of weeks, long after the initial inspiration has fled. With most oil painting mediums, what is gained in 'immediacy' is lost in luminosity and vice versus.
Traditional meglip is thixotropic, meaning that it changes viscosity in response to mechanical action. Stir a little glob of gel with your brush and it turns into a freely flowing liquid. Once on the canvas it gels and doesn't get disturbed by the next fluid brush stroke. Your brush strokes stay clear and the colors don't mix with the wet layer underneath. This allows the artist to continue painting without waiting for the first layers to dry. Neo-Meglip mimics the thixotropic quality of Maroger's medium by stiffening after application; however, unlike real Meglip the initial fluidity cannot be regained by mechanical action. Once Neo-Meglip is stiff, it stays that way.
The bristle grooves of your brush strokes will round out as Neo-Meglip dries, just as they do with stand oil and other alkyd mediums. If you are of the opinion that sharp bristle marks give the painted surface more character, then you won't like Neo-Meglip. Personally, I find them annoying; the highlights they produce force you attention to the surface of the painting, instead of the image I worked so hard to create.
I use a couple of drops on the end of the palette knife for an inch of paint out of the tube, although this varies by color. It takes more Neo-Meglip for lean colors like yellow ochre. The paint should have a nice glossy appearance and have the stiffness of soft butter.
As binding mediums oxidize, long polymer chains form that interconnect and envelope the particles of pigment, holding them in place. One of the many problems the oil painter has to deal with is the tendency of certain colors to chaulk over with an undesirable lack luster matte finish.
One cause of this problem is the medium sinking into the previous layer, either the under-painting or the gesso. Imagine setting a wet sponge on a dry paper towel with the towel drawing the moisture out of the sponge. In the same way, the lower painting layers suck the medium out of the top layer. This is often the case with acrylic grounds. Absorption is good for durability because it helps the top layer bond with the lower; however, this advantage comes with a price. The top layer of pigment becomes fragile, unsecured by an adequate amount of binding medium. "Oiling out", restoring the gloss by rubbing a thin layer of medium over the chalky areas, is the best practice, but there is always the risk of adding too much medium, which will eventually grow yellow and dull.
The second cause for chalkiness is that some colors naturally have a higher pigment load and are made with less binding medium already in them. This is particularly true for the earth colors like yellow ochre and raw umber. With experience the oil painter learns how much medium is needed for the paint to dry to a gloss, despite absorption into lower layers. The choice of medium is critical. Alkyds impart the same level finish as stand oil, but they dry too fast for me. Neo-Meglip has a longer working time than other alkyd products, but still dries to the desired gloss.