The misconception of a secret medium comes from drawing conclusions based on observation and some false conjecture. This misconception was substantiated with poorly executed scientific analysis from a period of time where the study of art materials was in its infancy.

A major part of the confusion stems from observing that old master paintings draw their allure from a high degree of transparency of the colors used by the artist. This erroneous observation documents what we now understand to be a physical property of painting materials. As many paints age, they become more transparent. Complex chemical changes in the structure of the paint, as interaction of lead white and components of the linseed oil in the binder occurs, turn the mixture into a metallic soap (a process that’s called saponification). This process makes the paint look transparent.

The old masters did not intend to have their pictures become transparent revealing underlayers in the painting, but the overall effect allows light to penetrate the surface and reflect in ways that give us the look we have come to accept as the style of old master artists. 

One of the major flaws perpetrated in the late 19th and early 20th century was the search for a medium that would produce the effect of this natural aging process. Those who studied the old masters came to the conclusion that a medium must have been used in the past to achieve the appearance of transparency we see today. Somehow the use of this medium was carefully guarded and not readily shared. Jacques Maroger was probably the most vocal and active of the art materials historians who supported the hypothesis of a secret medium. 

Maroger went even farther by producing a number of mediums that incorporated boiling linseed oil with lead, combining it with a resin varnish like mastic, and processing it until it yielded a brownish black gel material. Early experiments by Maroger are both amusing and frightening, as he mixed both leaded oils with water-based materials to create some horrifyingly unstable painting mediums. By the time Maroger settled on a painting medium that suited him and that he thought was the secret of the old masters, he had only succeeded in reinventing a well known 19th century painting medium called “megilp.” Unsafe to make, as well as a disaster to use as a painting material, megilp was known to be unstable and unreliable to painters living during that period. 

This is a simplified explanation of a much larger issue, but illustrates the point that experimentation with mediums that contain a complex mixture of components has potentially undesirable consequences, if inherently unstable materials are used.  Unfortunately, it has nearly been the rule that “old master” medium creators choose components that are unstable from the start; then they combine them with stable and other potentially flawed materials and expect them to behave well together to create a superior painting medium. One rule to remember is that mixing unstable components with stable ones does not create benign combinations. The inherent properties of the problem materials will show their nature and react in unsuitable ways.

This argument for a secret medium has repeated itself in countless ways. If you do a web search, you’ll find manufacturers who tout possession of the secret medium of the old masters. Amber mediums, a variety of Maroger-like substances, black oils, and gels made by small manufactures dot the painting marketplace. Even mainstream manufacturers have bought into the hype and created reproduction 19th century mediums using recipes from that time period. Do not confuse these mediums with alkyds and other modern synthetic materials that exploit the potential virtues of painting mediums without the vice of unstable chemicals.

A few voices in the painting world proclaim what exotic medium suppliers do not want anyone to hear. The secret of the old masters is that they were highly gifted and skilled painters, not amateur alchemists who dabbled in trying to make chemistry substitute for hard work and diligent practice. 

P. T. Barnum was a great student of the human condition. He knew that people could be duped into quickly parting with their hard-earned money for an ephemeral thrill, a cheap curiosity. Today, painters are ripe for the taking. They are naturally inquisitive experimenters who seek to push techniques and materials to the limits of their physical properties. Advertise a short cut or a way of achieving a look and feel of an icon of the art world, and they beat a path to the door of the manufacturer who is selling a little “miracle in a bottle.” 

I don’t deny that some of these materials will perform in remarkable ways. However, the long-term consequence of using mediums with unstable components that will destroy the integrity of a paint film so that the picture darkens, becomes difficult or impossible to clean, or flakes away as the paint become extremely brittle, seems not to matter to a number of artists. Their argument is that they have been using this medium for 20 or 30 years and nothing bad has happened. With a few of these flawed materials, the detrimental effects will not be apparent for upwards of 70 to 100 years. It may be a consolation to the artists who realize that they will not be around when the damage starts to manifest itself, but it is little solace to the owner of a painting who, having paid a high price for a work of art, expects to pass this treasure on to young family members so that they may enjoy it.

Making a painting that lasts is a tricky business. Time, natural deterioration of even the most stable materials, fluctuating environmental factors and transportation—all work against the artist to assure the potential destruction of the work of art. A lot of thoughtful care has to go into the preparation of the painting support, paint selection, surface treatment of the finished painting, framing and selection of a suitable viewing location in order to make a painting last.

Proactive methods and techniques will be the topics of discussion for future entries. Comments on old master mediums are welcome. This debate is far from over and every generation picks up where the previous one left off—to reignite the potential merits and flaws of mediums painters use.