Gamblin has dedicated vast amounts of time, research and development and has given generously in an effort to teach us about their products and guide the painters who use them. Here is what they have to say about Painting Mediums.
"Understanding the physical properties of their mediums can help painters better control the working properties of their oil paints. Painters who only use a medium to increase the flow of oil colors can be satisfied with a favorite teacher's medium or one from a book. However, painters who want to explore new ways to make marks or want to explore historical techniques, need to make a custom medium. They can combine contemporary materials to create the properties of traditional mediums and reduce their exposure to toxic materials. Or they can create a completely new combination to make a unique and personal medium.
By understanding the physical properties of mediums, painters can, for example, use Galkyd to replicate a high viscosity traditional painting medium, containing stand oil, dammar varnish and turpentine. Both mediums will be sticky with the same gloss level and good adhesion. Because Galkyd is made with Gamsol pure odorless mineral spirits, painters can eliminate their exposure to toxic turpentine and still use a painting medium with traditional working properties.
Painters for centuries have believed that the Old Masters had secret formulae that gave their paintings special optical qualities and archival qualities (permanence). By analyzing old paint films, conservation scientists are helping contemporary painters understand the Old Masters did not have many secrets. According to scientists of the Rembrandt Research Project at the Rijksmuseum, Rembrandt did not use mediums that contain resin varnish. He used the oldest painting medium: a simple mixture of linseed oil and solvent.
Adding natural resin varnish to painting mediums was first used as a studio practice in the 18th century. Before then, natural resin varnishes were commonly used to unify the surface of paintings. Some oil colors dry into matte surfaces and some into more shiny. Sir Joshua Reynolds was among the very first to use resin varnish in his mediums because his patrons wanted their portraits to look like those of the Old Masters. To accommodate them, Reynolds added resin varnish into his paints to give them a "gallery tone," a brownish yellow color of aging natural resin varnishes. He, in effect, artificially aged his own paintings!
"Natural resins, such as gum mastic, and since the 19th century also dammar resin, were and are uniformly appreciated for their optical and handling properties. Unfortunately, these tree exudates, chemically belonging to the class of triterpenoids, are also among the least stable of artists' materials. Particularly, when applied as a thin layer onto the surface of a painting, rapid degradation occurs due to oxidation and other reactions. Eventually, the varnish will obscure the paint layers because of loss of transparency, advanced yellowing and cracking," according to conservation scientist E. Rene de la Rie, in his oration Conservation Science Unvarnished.
Adding natural resins, litharge ("black oil," lead boiled into linseed oil) among other toxic materials would not have continued into the 21th century if artists did not enjoy the special "feel" of these mediums, the most famous of which is now called Maroger medium. Originally, its name was Megilp or Megilph. During the 18th century, artists realized that by using oil boiled with lead, a common practice used to make linseed oil dry more quickly, and then adding mastic varnish, they created an elegant, silky soft gel. Turner used such a soft gel medium in his atmospheric glaze layers. By the end of the 19th century, artists realized that adding Megilp accelerated the aging of paintings, making them dark and brittle.
A conservation scientist at the Tate Gallery, which houses many of Turner's great later paintings in London, gave Robert Gamblin a sample of genuine Megilp. Immediately Robert realized Megilp is unique and a valuable painting medium despite its obvious drawbacks. Megilp thins oil paints but still gives them body. During the next two years, he formulated Neo Megilp without using toxic lead, turpentine, or natural resin. With a base of alkyd resin, Neo Megilp gives painters a new tool—a soft, silky gel that may enhance the life of their paintings."
