One issue that tends to be super-annoying for some painters that are aiming for a more rendered image with a smooth surface finish is the “seams” that can occur in early paint layers. A paint seam is a perceivable variation where two paint films meet or overlap. And yes, the annoying little buggers can be downright infuriating.
One of the ways I try to minimize the issue is by tapering off any relatively sharp terminations at the end of the painting day (b). I will then “taper-in ” to these “tapered-out” endings with subsequent paint, trying to keep the paint film’s topography as even as possible. As some of you may already be aware from my previous writings on painting, I almost never establish foreground information (i.e., a subject) without some partial surround (i.e., background) for context. This means that most objects that I paint will have a tapered halo of the surrounding environment (a) ©. Now while all this tapering does indeed diminish some of the magnitude of the surface variation—the seams may still be quite visible.
In some cases, the visual disparity of the seam may be more or less noticeable due to the opacity of your paint. I have dubbed this issue the “aggregate problem." One of the main causes of this problem is when one, some, or all of the colors in your paint mixture is/are not opaque. When layering with non-opaque paints in the mix, the surface appearance will likely be an aggregate of the layers and/or potentially the ground.
(Region 1 and region 2 are the same when applied to the same ground–yet, when they overlap (region 3)
Another way that artists experience this aggregate problem is when they carefully and thoroughly premix the exact color they need for a particular region of a painting (e.g., a large homogeneous background). They assume that the premix will allow them to perfectly match the initial application with any subsequent addition. Often, the artists is surprised to see that the subsequent applications of the premixture do not appear the same when placed on top of an earlier application of the same mix (putting aside any influences from sinking, “suede” effect/brushstroke directions, topographical changes relative to the painting’s light source, etc.)
NOW THIS IS IMPORTANT: Some of you may be tempted to sand down these seams after a first layer. DO NOT DO THIS as it will just lead to additional (and probably more topographically severe) unwanted disparities. Rather, try to cover the seam appropriately during the next layer and wait for it to be dry to the touch. When it is so, feel the location of the covered seam (gently) with the dorsal side of your index finger to see if you can detect the surface variation. If you cannot, it is likely that you will NOT need to sand anything. However, If you do feel the seam, you can very lightly sand the area as needed.
In my current painting you can see the many seams and variations in my first layer (left). However, you can see how the seams have greatly diminished in appearance after the second layer (right), although they are not completely gone. This will need one more layer to really be pristine (with a little dust removal to boot.)
Now some may also be quick to ask if this issue of seams has anything to do with “sinking in.” While they can indeed be intertwined in the context of a painting—the issues are fairly different:
Sinking-in describes a change in the appearance of a paint film due to the oil of one paint layer “sinking-in” to a previously applied layer or a ground that is too absorbent or unevenly absorbent. Sinking in can also occur if there is excessive use of a thinner with paint which can weaken the binder’s capacity to form a film.
The seam issue is a matter of uneven surface topography or the effects of varied translucency encountered when attempting to join (or overlap) a new application of paint with a previously established one. Sinking can definitely contribute to the apparent severity of perceived seams while regions with overlapping tapers (where seams may be found) may indeed have sunken regions.