Originally written and published on the Natural Pigments.com website

Mediums to painters can be like a political debate.  There are pro-Maroger, anti-Maroger, pro-natural occurring resins and anti-natural occurring resins as well as pro-alkyd and anti-alkyd proponents.  The evidence is always about potential cracking, lack of adhesion and yellowing.  I have always been a curious type and I have experimented with almost every medium component that I could get my hands on.  However, if you are new to painting it might be logical to experiment with the paint right out of the tube so that you can understand and fully integrate into your procedure what the paint can do without additives.

 I have just tried to sit down and list some of my thoughts concerning the subject. Much is left out, and much is ignored but I thought there might be something here to promote discussion. I have spent a considerable amount of time during my 40 year career on experimenting and attempting to understand how different medium formulations work and why one would choose to use them in the first place. All of the statements that I am making are opinions or conclusions that I am drawing from trials, experimentation and in some cases constant usage. Some of the statements are very general because whether the medium materials work for you like they work for me is related to environmental issues of substrate, ground, etc.

Salvador Dali in his book, “50 Secrets of Magic Craftsmanship indicated that oil painting is basically about controlling viscosities of the paint. It has taken many years before I fully realized the impact of what he was saying. Mediums can be used for different purposes. Some people use mediums in alla prima painting to change the working properties of the paint. This would include-making it dry faster, making it slippery, making it drag, making it glossier, or matte, or simply changing the viscosity of the paint. Some painters like to put a few drops of medium component in their paint, some like to dip occasionally (I refer to this as a migratory dipper bird), and some like to create a wet cushion to work into. Of course, there are a fair number of alla prima painters that use no medium at all. The working properties of oil paint without medium in various states of drying on the palette can also be interesting. For the first ten years of my career, I was an alla prima painter. When I used mediums during this period, I used the migratory dipping bird technique. This was not particularly efficacious because some areas became quite oily and glossy and some areas were drier, causing a non-uniform surface with varying surface characteristics and resultant adhesion uniformity problems.

In layered painting processes, the basic reason to use mediums aside from the mechanical benefits is to create a translucent series of layers. Mediums help create translucent passages which act like a series of stain glass windows stacked on each other. How effective this is depends on the nature of the medium elements and how much paint is put on the brush. If the brush is loaded or choked with paint, then quite probably the paint layer will be more opaque. In general, depending on artist’s objectives, it looks very nice to have some opaque passages in areas of light (higher chroma areas) and some transparent passages in the shadows (lower chroma areas). This gives a variation to the surface that can be nice.  Now using mediums for glazing is not the only way to achieve glazing but it might be a bit safer tan using solvent to thin down the paint for translucency.  Because adhesion problems can occur from under bound oil paint.

There are an endless series of mediums that will work very nicely together and produce wonderful results. Using and experimenting with mediums have a lot to do with the personality of the artist. Some may feel that experimenting with medium components is dangerous and have do so with great intrepidation. Others by nature love to try new things. There are a few basic concepts to watch out for- first, the layers must be equal to slightly oilier as you go up in layers in order to promote good adhesion, There are “degreasing” fixes that have been used and seem to work, but in general it is better to build a layered painting with increasing levels of oiliness. I have had success in labeling mediums by percentage of oil excluding balsams, resins or siccatives in the calculations. But you must consider amount of solvent which does have an effect on the percentage of oil in the medium.

In experimenting with mediums, one of the most important considerations is the viscosity of the medium for the conditions of the painting. Viscosity must be adjusted for the following-the substrate that you are working on, the type of ground that you have used and environmental conditions of heat and humidity as well as the nature of the brushes you are using. Let’s break this down. Panels are generally more slippery than canvas with their peaks and valleys; Paper also is smoother and slippery (depending on the ground used). Canvas usually has a bit more drag unless the ground is troweled on to simulate a panel which covers up the peaks and valleys. Acrylic grounds vary in the amount of porosity depending on the formulation and offer considerably more drag than oil grounds. Hot and dry climates seem to set mediums faster and provide a little more drag than colder more humid climates. Softer brushes, such as natural hair and synthetic (acrylic style) are frequently better for glazing and scumbling. Hogs bristle brushes tear up glazes and make smooth even translucent layers difficult to achieve. So the mechanical properties of working mediums should match the conditions that you have set up. When the medium is in harmony with the conditions that you have set up, namely the substrate, ground, brushes, level of environmental humidity, then a certain nirvana takes over and the glide of the brush with perfect viscosity occurs.

There are hundreds of different medium components which all have their own separate viscosities and working properties. There are oils, balsams, varnishes, solvents, siccatives and “other” which might include waxes, etc. I am going to try to give a few observations about the various medium components.

I. Oils

A. Linseed Oil Family

1. Cold pressed linseed oil

2. Refined linseed oil

3. Stand Oil

4. Sun-thickened linseed oil

You can find technical descriptions in books about the make-up and manufacture of medium components in many different books. So I won’t duplicate much which has already been repeated. Cold pressed linseed oil is quite yellow in appearance and frequently has naturally occurring contaminates called “the foot” which make for a stronger film but refined linseed oil which is paler in appearance and is without the contaminates each has their own advocates.  I suppose it comes down to a trade off. Most  users would never experience the differences because from the standpoint of viscosity they act about the same-very slippery, very oily. Stand oil and sun-thickened oil can be very syrupy like molasses depending on the manufacturer. So the viscosity of these linseed oil family members differ greatly from refined to say sun-thickened. Panels with oil grounds greatly benefit from more syrupy oil due to their smooth non-absorbent surface and canvas with acrylic based grounds are more porous and have peaks and valleys and can benefit from oilier cuts like cold pressed in matching viscosities with materials. It is good to know the properties of some of the medium components but it is the total viscosity of the combined medium components which is the ultimate ruler.

B. Other Oils

A. Poppy seed Oil

B. Walnut Oil

C. Clove Oil

D. Safflower Oil

This list of other oils is not meant to be all inclusive. These are some of the non-linseed based oils that I have experimented with. Poppy seed oil is very light oil and is a bit slower in drying than other oils; it also forms a slightly less strong adhesive bond than linseed oil. What I like about both poppy seed oil and walnut oil (apparently so did Leonardo) is that they do dry a bit slower and are very effective in seamless blending of layers. I have felt that their smooth blending abilities particularly walnut oil is wonderful in producing smooth pure gradations of tone. I have generally stayed away from safflower oil, although it is used in some whites and yellow, it is a slower drier and offers no mechanical advantages over poppy seed or walnut oils. Clove oil is an interesting product. It can keep paint wet for 20-30 days. At one point in my career, I did these unbelievably complex palettes of many colors, chroma's and hues. I put in clove oil and kept these mixes wet on the palettes for nearly a month. Then I used a wet cushion which included medium components that dried quickly-so I had wet paint on the palette and dry paint on the painting surface. The best of both worlds. This was a passing phase; I would not recommend such bizarre approaches. But clove oil does have the ability to keep paint wet for an extended period of time. Longer on non-absorbent grounds and a slightly shorter period on absorbent grounds.

C. Balsams

1. Venetian Turpentine

2. Oregon Balsam

3. Canadian Balsam

I have tried all three. Oregon Balsam can be a little dark. All are very, very syrupy which increases the viscosity of mediums. I have more frequently used Venetian turp due to the availability and performance. Venetian Turp is generally reserved for the upper layers. It produces a wonderful gloss and has wonderful mechanical properties for blending. It really does not seem to affect the oil content of the medium for calculation purposes but, it should be reserved for the last several layers in a multi-layer painting-otherwise the surface gets much too glossy and subsequent layers, unless they are fatter in oil content will have a hard time adhering properly. Canadian Balsam has advocates that consider it to be superior.

D. Solvents

1. Gum Turpentine

2. Deodorized or low odor mineral spirits

3. Oil of Lavender

I have rarely used Gum turpentine in medium formulations unless I used dammar which doesn’t like mineral spirits and is not soluble in it.

The odor of turps is too strong for artists that work 10-12 hours per day. Most all medium formulations will work well with mineral spirits. I have used oil of lavender as an additive to palette paint if I wanted to refresh color that was in the process of drying. The interesting property of oil of lavender is its perfume-like smell and the fact that it volatizes more slowly out of medium formulations than other solvents. That is an advantage for some techniques. The percentage of solvent has an effect on building layers. A greater percentage of solvent will dilute the amount of oil causing bubbling up and lack of adhesion. A decreasing amount of solvent is necessary as you go up in layers unless you completely change the constituent elements of your medium formulation. I like to label my mediums by percentage of oil but I am also very aware of the amount of solvent by percentage in each one.

E. Resins

1. Dammar

2. Copal

3. Amber

4. Mastic

5. Alkyd

One of the major problems throughout the history of art is naturally occurring resins which of course are used to make varnishes. Varnishes are not just used for final coating of paintings; they are an integral part of medium formulations. Dammar and mastic are soft resins, copal is a semi-fossilized resin and amber the hardest of the resins is fossilized and made with great difficulty, great expense and great heat. There were many other inferior resins used from the 1400’s on and many of the paint layer problems, (this is my opinion) were caused by naturally occurring resins because of inconsistent production and the fact, that many promoted cracking. Now a resin varnish ideally is suppose to do a few things in the best of all possible worlds. First, it is to resist cracking and promote strength in the layers. Second, it is suppose to promote adhesion. Third, it should help with resistance to abrasion. Fourth it can impart gloss and saturation. It can assist in the drying characteristics. The ideal resin varnish that meets these ideals is one not available to the old masters. It is the synthetic varnish, alkyd. It is available by several manufacturers’ including-Windsor Newton’s Liquin and Bob Gamblin’s, Galkyd. They are available in several different versions and cuts. My belief is that alkyd resins are perhaps the greatest innovation since the 1400’s for the oil painter. I found out early that if multi-layer paintings all contained a little alkyd in the medium formulations that it built very strong uniform layers that offered all the benefits mentioned above.

Now, I have tried amber and it is a nice product which dries very hard. But, in truth it offers no benefit beyond alkyd which also dries extremely hard. I would also be willing to bet that on canvas with expansion and contraction, alkyd would have a tendency to crack much less frequently than amber. The other problem is amber is very expensive. Copal has advocates including the late Taubes, but it is so inconsistent in manufacture that you never know how well it’s made and it is very dark. Softer resins like mastic and dammar are ok in some medium formulations. The Maroger medium using mastic is a pleasure to use and I have had no ill effects in its use on panels. Generally I have not used it on canvas. These varnishes may work ok on final varnishes after the picture is dry, but they can not stand up to the superior qualities of alkyd for use in medium formulations. As such, I have had virtually no layer failures with many different medium components when an alkyd is used in the formula.

F. Waxes

1. Dorlands

2, Gamblin cold wax

3. Bleached wax

4. Unbleached wax

5. Maroger “titian” wax medium

I have frequently experimented with wax based mediums including cooking my own because I like my canvas paintings to have a slightly matte appearance and my panel paintings to be glossier. One of the things that I have been working on for some period of time is creating a translucent glazing medium for a wet cushion that is strong, resistant to cracking and slightly matte in appearance. Dorlands seems to be ok as an additive to the paint to make it matte but I have not used it much. I have more frequently used Gamblin cold wax which is a wonderful product to add to paint to reduce gloss. It sets well, keeps pretty fresh on the palette when covered and seems resistant to cracking. But, I also needed a glazing medium used as a wet cushion which would render paint layers translucent and matte. I achieved this through a home cooked medium of unbleached beeswax, galkyd, raw linseed oil, and turpenoid. It produces an incredible medium for matte translucency. The interesting thing is that because it is matte, it does not seem to show the layering to the same extent as gloss mediums. You get an incredible range of optically blended values, hues and chroma without the appearance of heavy glossy glazing.

The Maroger wax medium that includes linseed oil, unbleached beeswax and lead is also a wonderfully sensuous medium to use when added to the paint on your palette and due to the presence of lead dries very fast.

I have come to the conclusion that in use of mediums, it is more effective to either put some in your paint to change the viscosity, or use a wet cushion or both can be employed. The least effective way of using a medium is to dip into it (migratory dipper bird) due to the inability to control uniformity and the resultant problems that are incurred.

I have experienced paintings that might have 12 layers and that for 1-3 layers, you can use virtually the same medium or percentage of oil before the painting seems to require a bit more oil. It does not have to be a lot more oil, just a little oilier. (Remember viscosity conditions must be tuned to the substrate, grounds, desired brushes to be used and environmental conditions).

Virtually any combination of the above materials can be used if alkyd is part of the formulation. Be sure to label mediums by percent of oil in the formula and take into account solvents by percent which influence the dilution of the oil. Ignore balsams and varnishes in the oil calculation but consider them as a percentage of the total medium ingredients.

The superior quality of alkyd is a uniting force in all multi-layered mediums. I would stay away from softer resin varnishes. There are many books written which give different formula for mediums, so I won’t list a group, be creative, don’t be afraid to experiment and take notes on what seems to work. Be aware of the viscosity of the medium for the substrate and the ground; if it feels too grabby add oil or some solvent or both to formulate the right medium. If it is too slippery, consider adding some more resin or a balsam (in the upper layers). Be sure that each successive layer is equal in oil percentage or slightly greater for proper layer building and adhesion. But above all, don’t be afraid. No one will die. The police won’t arrest you. You may discover a wonderful combination of materials with exactly the right viscosity to produce a master work. And if the wet cushion that you apply doesn’t seem quite right, wipe it off and reformulate it to get the viscosity and working properties that you like. Cheers.

Now those whose job it is to patrol such bastions of inexactitudes and generalizations will have lots to critique in the above writings. That’s ok. But, take it for what it is worth and realize that because of the number of variables in substrates, grounds, brush types, and environmental conditions, it is hard to make iron clad statements about what will work under all conditions. What I have tried to do here is inspire thought and questions, and give some practical conclusions drawn from much experimentation. I have not tried to list the chemical formulations of the above medium components; others have done that in technical manuals. I have tried to give a practical usage guidelines on a much more informal basis as well as promote the idea that medium usage can be as creative as the actual paintings.