Mediums

[Catherine Ingleby]

I am very interested in the various mediums that are used, namely in the components that go into them and the different benefits/disadvantages. I use a medium that is one part refined turps, one part canada balsalm and two parts sun thickened linseed oil.

I find this to be the most effective when blending or softening as it will drag a sufficent amount of paint without losing the the shapes or contours. It tends to just pull the uppermost layer of pigment. This medium is also ideal for glazes and dries quickly enough that the same area can be glazed over the following day without risk of an opaque or cloudy effect from the paint underneath.

I tend to dilute this madium with refined turps when laying in and to use less in the final stages of the painting as I put down impasto highlights.It also works well as a re-touch varnish when the paint sinks into the canvas.

The only disadvantage of this medium is that, if too heavily used, it can make the painting slick and oily. This makes the surface far harder to paint on but can be remedied either by scraping down when wet or, if dry, sanded down with cuttlebone.

Please could anyone who makes their own medium tell me a bit more about which ingredients they use and why?

[Virgil Elliott]

In general, the less medium one uses, the stronger and more permanent will be the paint film. Mediums are analogous to mortar in masonry, with the particles of pigment analogous to the stones. The stronger structures have the stones resting on one another, held together with a minimum of mortar. Too much mortar and too few stones makes for a weaker structure. The paint already has enough binder in it as it comes from the tube to function optimally as paint. If it is too thick to control, it is often due to the manufacturer's having added too much aluminum stearate, which thickens the oil into more of a colloid (gel) than a fluid, in which case a switch to another, less adulterated, brand would be preferable to adding more medium to it to overcome this stiff consistency.

Many popular medium ingredients also bring various problems to the paints that could compromise the permanence of the pictures in which they are used, the consequences of which would not show up for many years. Whereas we often hear painters attest to having used "X" with no problems, we must realize that these reports represent only a few years, and cannot be taken as conclusive evidence that "X" is therefore archival. Medium additives known to cause problems include all balsams and natural resins, wax, and certain driers. Whereas one might get by with using one or another of these substances in very small amounts, it is usual for artists who place an inordinate amount of importance on mediums to use them too liberally for optimum permanence. Unfortunately, there is a great deal of erroneous information in circulation adding to the confusion on this issue.

The least problematic ingredients for mediums are linseed oil and walnut oil. These may be thinned with odorless mineral spirits somewhat, but it is best if the solvent component of a medium is no more than half of the overall mixture. Linseed oil gives greater film strength than walnut oil, and dries faster, whereas walnut oil yellows less than linseed, and allows longer working time wet-into-wet. Both have a long and successful history of use by the Old Masters. What is not widely understood is that the yellowing associated with linseed oil is reversible, and in fact disappears by itself in a few years of normal light exposure. The process can be accelerated by placing the yellowed painting in outdoor light for a few hours a day for several days in a row. Two or three days will usually suffice. Most of the yellowing we see in old paintings is in the varnish, not in the paint itself. Where the paint itself is yellowed, it is usually due to resins and/or oils cooked with driers in the paint medium. This type of yellowing is not reversible, which is one reason why it is best not to use those ingredients in our painting mediums.

Portraits become family heirlooms, and if we have charged a significant amount of money for them, the clients and their heirs have good reasons to expect them to last for centuries. It reflects negatively on our profession when our pictures fall apart, darken prematurely or develop other problems due to poor choices of materials or practices on our part.