“Sinking in” is the term used to describe what happens when a layer of paint loses its saturation. If you, like me, often use an earth palette, then this effect can easily be seen when a layer of Raw Umber or Burnt Umber has dried.
So why does it happen and what should be done about it?
It seems a simple question to a problem I believe is rather ubiquitous. As such, a straight-forward explanation and solution should be easy to find, right?
Not so. My understanding of the problem has evolved over the decades in an organic fashion, but never had I found what felt like a clear and direct diagnosis. Until now. What follows is an explanation I discovered that makes perfect sense… from a book published in 1912: The Technique of Painting by Charles Moreau-Vauthier.
On page 105 of the publication (page 157 in digital format) he introduces the topic with the following commentary:
Artists’ colourmen are often reproached for putting too much oil in their paints. They reply that the generality of artists prefer their paints thin, the true reason probably being that dealers are able to keep such colors longer. Some artists, on the contrary, spread their colors for a few minutes on blotting-paper, knowing that oil, in spite of the service it rendered, is a destructive agent.
The effects of its presence proclaim themselves as once in many cases by the sinking in of the paint. I will speak presently of the deterioration of color. The sinking is not, properly speaking, deterioration; it is due to the displacement of the oil in the impasto. The painter is not much disturbed by it, but it is an annoyance to him when he wishes to fuse a new pass with one already completed and when he wants to judge of the general effect.
To explain why this happens and what to do about it, he goes on to say:
If a layer of color be laid upon a porous material or another layer of coloue nor perfectly dry, it sinks in; that is to say, the oil, instead of remaining equally distributed round the particles of colored powder, travels between the particles, and soaks into the porous matter or the older layer of color, which is itself porous if not perfectly dry; the powder, thus deserted by it agglutinant, assumes a dull, indeterminate appearance, especially in the shadows, to which the oil had given depth and transparence. All that is required is to restore the oil the color has lost, or to give it a coat of varnish, the resin of which will fill up the pores of the colour abandoned by the oil; the paint will then recover its transparence and its liquid appearance.
As a special bonus, the author goes on to address another problem that has at times vexed me (see the following post); what to do when the mix of paint and medium ‘beads’ on the surface, i.e., when it looks like water on a duck’s back. He writes:
If the artist paints upon a stratum the pores of which, though empty of oil, have condensed so much in the process of drying that they do not absorb the oil of the over-painting; there is no sinking in, but the impasto lacks cohesion; as the oil of the new stratum does not take root in the stratum below, there is no complete adhesion, and the durability of the work will not be assured. Each time that the painter wishes to add something, he should use a re-touching varnish capable of uniting the strata and thus ensuring the homogeneity of the picture.
To the above I would add that it may be necessary to take take a rag, rap it around your finger, dab it in some oil, then some pumice powder and lightly sand the surface. You could even use some light sandpaper. He concludes with the following:
Broadly speaking, the traditional precept: load the high lights, and keep the shadows thin, will be found the safest rule, and the one most in accordance with the resources of the process. The loading of the high lights enhances their reflecting power, while the lightness of the shadows give more freedom of effect to the oil and the varnish.
I hope that helps you as much as it did me. Please feel free to leave your comments below.