Just a few follow-up thoughts to my recent article for Natural Pigments article might be in order.  I would like to reiterate and expand a little on the popular notion of giving medium formulas without contextual explanation.  Medium formulas must be viewed as contextual recommendations and be subject to the conditions that govern the use of materials.  As stated in my article, one variable factor in the performance of mediums is the substrate.  Canvas performs different than panel but, more specifically, different kinds of canvas provide different environments for the medium.  The roughness of the weave of the canvas is significant,  is it portrait grade linen, or fine texture cotton , is it a medium grade hemp, or is the linen that is enormously textured with high peaks and low valleys.  This variable will affect the dispersion of the medium and cause medium to collect down in the lowest points and be relatively unavailable in the high points.  Canvas can tolerate oilier mediums than panels due to the texture.  If the medium is too oily on a panel it is like ball bearings on a frozen pond.  I like a more viscous and sticky medium on panels.  This can happen with heat bodied oils and Venice turpentines.

Panels are more uniform in texture, so the variable here tends to be the ground used on the panel.  See next paragraph about grounds on canvas.  However, I have recently found some commercially prepared panels on Masonite (hardboard) which are coated with an acrylic ground of some unknown formulation which are reactive to oils and can cause the ground to re wet and become sloggy in reaction to oils and mediums.  I would presume that the “acrylic” ground has some other components which are re wetting the ground.

Returning to our canvas example, I have used many kinds of grounds over the years on different texture and weight linen, cotton and hemp canvas.  I have used acrylic based grounds, skin glues and oil grounds, as well as a ground used by the old masters called a ½ oil ground over skin glue (one that was made by David Davis and is similar to the formula used by artists as early as Titian).  Grounds make a significant difference in the performance and handling qualities of the medium.  Acrylic grounds tend to be a bit more absorbent and cause more drag than oil grounds.  The ½ oil ground is very, very absorbent and has some of the same qualities as a true gesso ground.  The mediums if too thin and not viscous enough absorb into the ground.

Another variable in medium use which is particular to artists that layer paint is the nature of the paint in the previous layer.  Some artists that layer, may use oil over egg tempera, or oil over egg emulsion, oil over water soluble oil, oil over acrylic, oil over glue based emulsion paint, oil over a layer of relatively fat oil paint or oil over a layer of relatively lean oil.  If you don't believe that the medium is affected by the layer that it is going over, try it.  If the layer is too fat, the medium will break into droplets and be totally unusable (there are ways around this problem, which are beyond the scope of this note).  Further, the abrasion of the previous layer is often beneficial to the adhesion of the next layer and the performance of the medium.  Oil accumulates on the surface and by use of a little steel wool it can make the surface receptive to the next layer of paint.  You also get a good idea of how well the layers are adhering to each other.

One variable that I have experienced in the Midwest is the performance of a medium in winter when the heat is on and the summer when the humidity is high.  Many of my mediums which were reliable and predictable dryers either dry too fast or too slow depending on the humidity and temperature.  This can make a medium that you like seem to have a personality of it's own.

Another factor in medium usage is the amount and the physical dispersion of the medium.  I have always told students that too much medium to work into was worse than no medium at all.  I prefer “wet cushions” as my application of choice and I generally use my hand to squeegee the medium until I get a very thin coat.

If the medium is brushed on and there is too much, it will actually make the paint process nearly impossible to execute.

Now what I am trying to say, is that the above factors form the context for mediums to exist in and whether you like it or not, your specific medium has to operate within many of the above variables.  How much the above factors influence the performance of the medium has to do with how extreme any of the variables are.  In some cases, if the variables are not too radical, a medium can work well for both a canvas and a panel or both an oil or acrylic ground.  However, just because it works, doesn't mean that you couldn't design even a better medium specific to the conditions.

Experimenting with mediums is fun.  As stated in my article, if you use an alkyd resin in place of natural resins, you have quite a bit of wiggle room to add components due to the stability of the alkyd resin and the resistance to cracking and abrasion.  If you want the medium to flow more use oiler components such as poppy oil, thinner linseed oil cuts or walnut oil.  If you want the medium to be more viscous consider using stand oils (heat bodied oils) or Venice turpentine in the upper layers.  Alkyd resin is a good base that stands central to a medium formulation and adds many benefits to the variables that you might add.  Now that does not mean that natural occurring resins are bad.  I have over the years used many copal varnishes, damar, mastic and amber and have not experienced any dramatically negative results as a whole (damar gets too tacky too quick and seems to produce too soft a layer for my taste).  I just happen to believe that alkyd varnishes have superior qualities to the natural varnishes and this has been proven in extreme tests under exterior conditions.  That is why most exterior oil based paints and even some acrylic formulated paints have alkyd resins included.  Their superior qualities have much to recommend them.

Begin to experiment with mediums and don't be afraid to make adjustments for the variables that you have in your specific painting protocol.

With all the above variables noted, I have begun to experiment with a wonderful new set of proprietary oils from Natural Pigment.  One of the first mediums that I have used is a very simple one:

1 part Natural Pigment boiled drying oil

1 part Alkyd resin Varnish (in this case Liquin)

1 part Windsor Newton rectified turpentine (not necessary that it be this brand turpentine)

This simple medium was used on two separate paintings.  One on panel with an acrylic ground and one on canvas with an acrylic ground.  During summer months in the Midwest.  The canvas was portrait grade.  The one on acrylic ground had an egg emulsion under painting and the one on canvas was painted over a lean oil series of layers.

This medium was wonderful to use.  It stayed open for an 8 hour painting session free of tack and easy to manipulate and then was dry to the touch within 24-36 hours.  The working properties of this medium which was used in a wet cushion and wiped down by hand was exceptional.  It virtually did everything that I wanted it to do and I would recommend it highly as it performed beautifully in both the canvas and panel.  I layered the same medium four different times with light steel wool in between layers.

There are several other Natural Pigments oils which I will be testing both in mediums as well as in paint making activities.

Many times I like my canvases to be a little more matte in appearance.  As such I have experimented with a medium containing beeswax.  In this case unbleached beeswax which some have advocated as superior in resistance to cracking than bleached beeswax.  Could be debatable, the color of bleached certainly is less amber in color.

My aim for this formula was to create a medium that I could use for glazing that would not be glossy but would be matte but still offer all the sensitivity of traditional glossy glazing medium.

As such I used the following.

3 parts by weight raw linseed oil

1 part by weight unbleached beeswax

1 part by weight alkyd resin (in this case Galkyd)

This was heated in a double boiler and then after it was taken off the heat

2 parts by weight deodorized mineral spirit (in this case Turpenoid blue can)

This medium was used on various grades of canvas with various grounds and has performed very well.  It was the first medium that has allowed me to glaze with a resultant matte finish.  I also brushed this on and hand wiped it to a thin layer.  I worked into it with normal oil paint.  The only drawback that this formula has which is typical of all oil that contains beeswax is that it is subject to scratching of the surface due to the softness of the wax.

Although I have used hundreds of mediums over the years, these two are very useful combination that I am currently enjoying.  But don't take these as Gospel, modify them according to your own variables and painting protocol.  Don't be afraid, experiment and have fun.