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Things that can Go Wrong in Oil Painting

© Susan A. Wenz-Denise

I have said before that oil painting is a pretty forgiving medium, but there are things that can go wrong and ruin your artwork if you aren't aware of them. The good news is that the most common mistakes are easily avoidable by following a few rules. Some damage can even be repaired.

The difficult part of assessing the quality of a finished oil painting is that it takes some time for it to dry and for the damage to appear. More specifically, after the painting has had enough time to dry and sometimes even longer, cracking or drying out of the colour can occur. In most cases the causes are easily identifiable.

Oiling Out
One of the most common and destructive effects of improper oil painting is the sinking of the top layer. This process occurs when the oil in the colour evaporates too quickly, and as such causes the layer to sink into the previous layer. You can tell your painting needs "oiling out" if your painting's overall appearance or certain areas are dull after the painting has completley dried and is ready for varnish. Not only does this drying out cause further concern of potential cracking, but it also creates an uneven, blotchy finish of the painting.

The main cause of a dull finish is from an incorrect ratio of drying oils to paint and solvents. More specifically, it occurs when there is too much of a solvent concentration in the paint. This is okay for early layers, but will cause a dullness effect in the top layer. Another common cause is an overly-absorbent painting surface. Be sure to use a well primed surface to avoid letting the paint sink into a porous surface.

Fortunately, "oiling out" is a way to regain the sheen of your surface. Oiling out is a process in which an all purpose medium like thickened linseed oil, diluted with 50% mineral spirits, is rubbed into the dull areas. Gently and sparingly rub in the oil mixture with a soft clean cloth and wipe off the excess, repeating until the painting has an even sheen. Applying varnish on its own without oiling out will not solve the problem. However, after oiling out and allowing the painting to dry thoroughly again, you may apply picture varnish as usual.

Cracking
When a layer of paint is significantly drier than the layer underneath it, the painting will most certainly suffer from a cracking effect. For example, if the underlayer contains more drying oils like linseed than the top layer, and if the top layer is diluted with too many solvents then the top layer will dry quicker and more brittle than the bottom layer. In turn, the bottom layer will cause the top layer to crack as it dries at its own slower pace.