I was in college, majoring in communications, when someone pointed out that some peoples dwelling in or near the northern polar climes have fifty words for snow because they have to "know their snow" in order to survive with it. Only recently, however, did I learn that in compiling a Scots thesaurus, researchers have actually logged 421 terms applicable to snow. (I can only speculate that somewhere in the history of Scots a significant part of the population shared my views of snow. That, however, is beside the point.)
Regardless of impressive tallies of terms provided in both cases, the principle involved is that a simplistic conception of snow cannot suffice for people who not only live and work in a snowy climate, but depend upon the snow for survival. Similarly, a studio artist must be able to look at dryness in terms of what can or cannot be done with paint at any stage of drying. And that involves at least two things: Knowing how to recognize a particular kind of dryness, and knowing what kind(s) of treatment a particular stage of dryness can withstand.
This is what I finally came up with as a way of not only conceptualizing dryness, but keeping track of what I can probably do to a paint layer or layers at any given time. Such a determination varies according to artist and a multiplicity of factors associated with tools, techniques, materials, etc. I needed such an approach in order to work effectively on multiple, concurrent paintings. These, then, are the stages of dryness I track:
Dry to solvent Dry to rag Dry to add Dry to touch Wet
Wet means that paint, in any degree, comes away on one's finger from lightly touching the surface of the painting. Included in Wet is the stage at which a light touch results in paint-adhesion to the finger, but does not pull paint away from the painting; in other words, the paint is tacky, but stays on the surface of the painting, not the finger. I do not track the tacky stage explicitly because, for my purposes or methods of painting, there is usually nothing I wish do with paint that is either wet or tacky.
Dry to touch means that the paint is no longer tacky. To be precise, this stage is often synonymous with Dry to add; however, the nature of the immediate underlayer, though dry to touch, might not be dry enough to withstand (a) the ways in which an additional layer might be applied or (b) the materials within the additional layer. For example, a dry-brush glaze is usually very, very thin. And no matter how dry to the touch such a glaze might be, any other attempt to add to it runs a high risk of ruining the glaze, hence the need to seal the dry-brush glaze layer before adding a layer to it. Provided, of course, the sealant will not disturb the glaze-layer. Knowing when a layer is dry to add, not just dry to the touch, is proably the most elusive or difficult distinction to make. In my experience, only experience can teach how to make this decision.
Dry to add means that the paint feels dry enough—which is usually a function of a paint-skin having formed atop a layer—being firm enough to withstand a light glaze or an impasto application. The application must, however, be gentle, depending (in part) upon the thickness of the layer under the skin.
Dry to rag means that the layer can withstand light or medium wear imposed by the use of a rag. Friction is the main factor (in relation to dryness) to be considered in ragging. Of course, topography in the substrata is also an important consideration because rubbing subjects peaks and ridges, in the substrata, to more friction than pocks and valleys experience, with the result that the elevated features of the topography can have the underlayers completely removed if one is not careful. This stage of dryness might sustain knifing, but I seldom knife at this stage.
Dry to solvent is a determination that has more to do with how long an area has been dry than with whether touch reveals anything. In other words, touch can sense dryness in both surface and substrata and it is that sensation which factors in decisions to add or to rag. A solvent, however, can sometimes dissolve all or part of a layer regardless of perceived dryness or its duration. If a solvent really is necessary, the longer the painting has dried, the better. Additionally, the length of time to which any layer will be subjected to addition, ragging, stippling, knifing, solvent, etc., is also a variable to be taken into account.
Making any of these determinations often involves standing still and quietly before a painting, closing one's eyes, and reaching toward the surface of the artwork to gently place the fingertips of the hand lightly upon the area in question. Touch becomes the primary means of "seeing" into the layers drying underneath one's sense of touch. How one discerns dryness can involve perception of coolness versus warmth, firmness versus softness, etc. Unfortunately, bad experience with substrata is probably the best way to learn how to see in this manner. And bad experience is an excellent teacher in terms of deciding what can and cannot be done at any particular stage of dryness.
It is usually a good idea to thoroughly examine the area in question, as opposed to sampling in an area. Drying and stability are not just a matter of the status of the chemical reaction within the most recent layer. Dryness also involves the interaction or lack of it between the most recent layer and any substrata over which a new layer will be applied. For example, I once applied a translucent glaze to a bone-dry painting consisting of two exposed layers, a Titanium layer over which a Burnt Sienna layer had subsequently been applied. Application of the glaze went swimmingly and I left the painting to dry, which it did; however, my eventual assessment of the dryness of the translucent glaze relied only on examination of the glazed area on top of the Burnt Sienna. Thinking all exposed layers were dry, I resumed work on the painting and discovered my error when a light ragging revealed that those areas—of the light glaze most recently applied—that were on top of the Titanium were as wet as when applied originally.
This screen-capture shows how I keep track of multiple paintings as they move through stages of dryness. The five projects listed constitute the active paintings on which I was working at the time. Dormant projects and projects still in research and planning are not listed. Vista and Lunta Copse are two large painting projects. Paintings without individual headings are sketches or much smaller projects that often serve as filler or grabbable projects for discretionary time (i.e., simple to set up, simple to clean-up). Benchmarks and History tend to be the same thing, serving as reference data or reminders for drying times affected by various configurations of materials, layers, etc.
This kind of thing is useful in planning and scheduling. It is also invaluable when the work of the studio involves experimentation with materials and techniques, which is actually characteristic of almost every studio project; for example, implementing a radically new palette, medium, etc., as described in Does painting have to be a matter of life and death?.