Thoughts on painting mediums

[Michael Georges]

Jennifer:

If you add a "drying agent", in the case of Liquin, cobalt dryer to your paint, IMO you sort of negate the whole concept of fat over lean. Fat over lean principles apply when you are applying paint in layers where you want a bottom layer to be dry before you put another over - or at least you want them to dry at a consistent rate with each other to prevent cracking of top layers from a bottom layer drying slower.

Drying agents like cobalt or manganese or lead circumvent that process by making the layers dry faster and more consistent with each other.

You will find differing opinions on Liquin, and on how to glaze. The beading is interesting and I suspect is is due to a slick surface combined with the use of mineral spirits (gamsol) over turpentine. Again, IMO, mineral spirits are great for cleaning brushes, but I don't bring it anywhere near my paint as I don't believe it works in the same way that turpentine does.

EDIT: I believe Richard Bingham understands this MS/OMS vs. Turps concept much better than I do and perhaps we can convince him to explain it. I remember reading the case for the differences on Cennini and thinking that it made a lot of sense.

[Richard Bingham]

Michael, the concept of "fat over lean" is actually something quite apart from how dry an underpainting layer is before continuing to overpaint, although that is certainly a factor in painting in a layered technique.

Essentially, "fat" paint contains a lot of vehicle . . . that can mean its "chubbiness" results from the addition of mediums of all descriptions, but "fatness" is also a function of the pigments involved. Certain pigments, (e.g. ivory black) are very absorptive, requiring a lot of oil to reach desirable working consistency as paint. Other pigments, notably most earth colors, have a low absorptive index, and so they are naturally "leaner".

The relative dryness of underlayers as one progresses with a painting is a factor in good painting practice. Continuing to work on layers that are touch-dry but not dry all the way through promotes build-up of paint layers that become a homogenous unit by forming a chemical bond through solvent transfer.

It's a good idea in general to avoid using cobalt or manganese siccatives in particular, because these compounds promote rapid drying from the surface inward, causing paint to "skin over" and effectively sealing off paint that is not yet thoroughly dry. The difference in drying rates and shrinkage can cause crazing and other defects.

The reason "good" turpentine is a better solvent choice than MS or OMS (both are petroleum distillates similar to kerosene, but more highly refined) is that hydroxides in turpentine react with acids present in linseed oil. The reaction binds ambient oxygen, which promotes thorough drying of paint films from the "inside out" as well as from the top down.

Turpentine is in trouble. In many circles, it is seen as a horrible, smelly, toxic substance akin to nuclear waste, while OMS is tolerated as being "safe" on the basis of being odorless . . . which is rather a dangerously uninformed point of view, since both turps and mineral spirits have a near identical vapor pressure. This means an open container of either will emit the same amount of hydrocarbons into the studio atmosphere through evaporation. Safe practice demands that all solvent containers be covered, and that studios have adequate ventilation.

For the past couple of years it has been nearly impossible to obtain "good" turpentine, i.e., the stuff that is distilled from tapping the gum of living conifers, a process similar to collecting maple syrup. Pure Spirits of Gum Turpentine is water-clear, and smells clean, like a pine forest after a rain.

What has supplanted "good" turpentine in hardware and paint stores is a foul-smelling distillate produced mostly in the orient by grinding stumps, limbs, slash and forest waste and steam-cooking the mash to obtain a liquid with the chemical properties of pure spirits of gum turpentine, but with other adulterants and a fair amount of free water. It is the camp-follower of deforestation, reeks of creosote, and should NOT be used at the easel for any purpose.

[David Clemons]

It's a pity that art supplies don't come with instructions or user manuals with an end chapter on troubleshooting or 800 numbers to call. I doubt it would improve things much if they did.

[Allan Rahbek]

I have made all the mistakes mentioned so far.

My Mona Lisa copy from 1969, one of the first paintings I ever did, is very dark because of too much medium and "refreshing" layers of varnish over time. I will do almost anything to avoid repeating that mistake.

I have settled on the use of what is called "Mayers Medium" which concist of : 5 parts Turpentine, 1 part Stand Oil and 1 part Dammar. This is not a quick drying medium but it does the trick for me. The mixture of 5 turps to 1 Stand Oil vill delute the paint without making it matte and the Dammar will speed up the drying a bit.
I think that it is the best compromize because it works for me, especially because it is now possible to buy Flake White here in Denmark ( Flake White, known to be a fast drier)

[Richard Bingham]

"Mayer's Medium" is what has been universally used in university art departments for over a generation. What has not been taught is an overview of sound painting methods and the nature of materials. While quite innocuous as a "medium", it's commonly used simply as a diluent in the absence of better instruction.

Information on the broad variety of handling characteristics paint additives (that may be properly termed " painting mediums") can present has been sorely lacking where art instruction has abrogated systematic teaching of the craft aspects of applying and handling paint in favor of promoting a "self expression" unfettered by considerations for the physical realities which materials in general present.

The presence of damar in the "Mayer Mix" is qustionable, as it adds nothing to the handling character of paints that varying proportions of oil and turpentine do not. Stand oil affects the nature of paint films more dramatically than damar, and may be termed a "medium" when used instead of an untreated raw linseed oil.

The recipe for Mayer's three-part recipe is perennially suspect, as more often than not, damar retouch is used, which is already diluted over 50% with additional turpentine, to the point the resin and oil are so over-extended their presence is moot, the effect being negligible if not unnoticeable.

To reiterate, painting mediums are not diluents; they are not siccatives.

Turpentine alone will reduce the viscosity of tube paint, as well as accelerate drying. Adding certain proportions of oil will prevent the paint from being underbound.

[Allan Rahbek]

I believe that it makes sense to name "Mayer's Medium" a medium because it is a mixture of oil and turps used to mix into the paint to control the workability of the tube paint.

I work mostly wet into wet over a thin wash of paint diluted with Vegetable Turpentine.

The "M's M" works better than using only turps when it is used as diluent in the paint.

The problem with "only" turps is that it makes the paint more lean and, in addition, it's difficult to control the viscosity of the paint using only turps, it becomes easily too thin and the turps evaporate too fast. The Stand Oil compensate for those three disadvantages.

It is correct that it's primarily for thinning purposes that I use it, but I find that it fairly neutral to the original tube paint composition.

When the painting is dry I will varnish it with a removable varnish.

[Marvin Mattelson]

Allan, personally, I avoid using Damar for any purpose whatsoever and make this a major point when advising my students of prudent choices for the best archival painting methods. Damar yellows and gets more brittle as it ages.

Unlike linseed oil, in which the yellowing can be reversed upon exposure to natural light, Damar's effects are irreversible. When used as a final varnish it becomes increasingly more difficult to remove and requires extremely powerful solvents to accomplish this. Many a great painting has been ruined through ill fated attempts at it's removal when used as a varnish. I just don't see the up side.

The vast majority of old master paintings have no evidence of Damar, or any resin for that matter, in the paint layers. From the 18th Century on there was a lot of speculation going on regarding the make-up of artist's mediums, particularly regarding artists from the 17th century.

Fortunately, modern science has disproved the bulk of this conjecture, so we can make better decisions than far too many of our forbearers.