Have you ever had a problem in your oil painting such as cracking or dull finish? 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 color can occur. In most cases the causes are easily identifiable.
One of the most common and destructive effects of improper oil painting is the sinking of the top layer, which causes a dull finish. This process occurs when the oil in the color
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 completely 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.
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.
A cracked layer in an oil painting cannot truly be fixed. Applying more paint or mediums will only compound the problem. As such, it is best to avoid this situation from the beginning. The easiest way to ensure that your painting dries at a healthy pace, so that no layers crack, is to layer in the correct order using the right mediums. A traditional rule used by oil painters is referred to as “Fat over Lean”, or flexible over less flexible. In other words, when painting in layers, the proportion of medium used in each layer should be increased. To give you an idea of healthy mixtures that can be used when glazing layers, here below is an example.
First Layer – VERY DRY – mostly solvents, little color
Second Layer – DRY – a lot of solvents, more color
Third Layer – MEDIUM – a little solvents, some drying oil, some color
Fourth Layer – OILY – little or no solvents, drying oil, color
Please note that the drying oil I refer to means an oil like linseed that slows drying time of the oil paint, and does not speed it up. If you choose to use a medium like Liquin that speeds up drying time, use it within the earlier or middle layers of the painting, or throughout the entire painting process. Fast drying mediums are ready-made and already contain a well-balanced mixture of medium and solvents.
Using too many different types of mediums, and/or creating your own mediums, can put a painting under “stress”. Damage is very unpredictable in this case. The easiest way to avoid putting your painting under stress is to adhere to the Fat over Lean rule. Although technically all oil mediums are compatible with each other, only one type of drying oil and solvents should be used within each layer. When using ready-made mediums, do not combine them with others, only solvents if needed.
So most problems with oil painting can be easily solved or at least avoided.
If you have had experience with these or other problems and have dealt with them successfully, I would certainly love to hear about them in the comments section below.