Art is one of those pursuits that benefit from continuing practice and analytical study, as well as reaching out in different media. As I delve more heavily into using oil paints, I am investigating the ramifications of a dilemma that long-standing rules of painting don’t appear (to me, anyway) to address sufficiently.
Traditionally, oil paints have been thinned with turpentine or other solvent for a looser, freer-flowing consistency, particularly in underlying layers that must dry before subsequent, “fattier” layers (with a higher proportion of oil to pigment). This approach is stated in two ways—“fat over lean” (meaning that layers with lower oil content should precede layers with heavier oil content) and “thick over thin” (meaning that thin applications should go down on the canvas before thicker, more viscous layers). A third “rule” is that darks go down before lighter values. The first two of these rules help to ensure that underlying layers set up firmly and dry before the upper layers. If the upper layers dry first, they are subject to cracking and possibly flaking off as the underlying layers continue to dry.
My dilemma arises through my preference to avoid using solvents. I’ve tried using water-soluble oils, but I don’t like the feel of working with them. The consistency and behavior aren’t the same as those of traditional oils, so I rely on thinning my paint with additional oil, rather than with solvents, even in the underlying layers. So what is the best approach to layering my paint under these conditions? By adding oil to thin the dark, underlying layers, it’s difficult (if not impossible) to maintain the fat-over-lean requirement.
I surveyed a number of colleagues who paint in oils, as well as a paint manufacturer (M.Graham) who advertises their paint as being ideal for solvent-free applications, to see what all of them would recommend. The results were overwhelmingly that thin, underlayers should remain low in oil, ideally being used straight from the tube. But “straight from the tube” is rarely (if ever) a thin application. And if subsequent layers of the tube paint should have any additional oil incorporated into them, they would necessarily be thinner, not thicker, thereby breaking the guideline of thick over thin.
So which rule takes precedence—fat over lean, or thick over thin?
In order to overcome the problem, I’ve decided to try mixing alkyd medium (which promotes more rapid drying) into my darks for the initial applications. This will allow the underneath layers to dry more quickly, before the later layers.
This brings to the fore a second but related issue: To speed drying, to more easily transport fresh paintings, plein air painters often like to incorporate alkyd medium into their typically slow-drying titanium white, which is used to raise the value of tube colors. For my purposes, however, it probably wouldn’t be advisable, as the alkyd incorporated into the value-raising whites would increase the drying rate for the later, higher-value layers. This would compromise the relative drying-rate difference between the upper layers and the initial underlying dark layer, in which the alkyd medium was used for thinning.
Although the manufacturer recommended against using both oil and alkyd medium in the same composition, I am inclined to overlook that guideline to allow me to use additional oil in any final glazes used to incorporate detail into the almost-finished composition.
If you have faced and found a solution to this same issue in your own work, I would be interested to hear how you resolved it.