Question asked 2016-11-30 23:18:54 ...
Most recent comment 2016-11-30 23:36:00
I see warnings of the possibility of graphite migrating to the surface of an oil painting over and over again.
I have been using graphite for over 40 years without seeing any migration, and considering that graphite is used as a pigment in oil, I'm inclined to think that graphite migration is a myth.
Is there any evidence that graphite can or does migrate through oil paint?
Note, I'm not talking about a drawing becoming visible because the paint over it has become more transparent over time.
Answers and Comments
Yes this is a COMMON myth and why we added it to our "Myths, FAQs, and Common Misconceptions" document that can be found in the Resources section. Just like charcoal, particles of graphite can become dislodged during the painting process depending on the size and shape of the particles and can therefore become incorporated into the paint (often less so than charcoal). However, graphite does not migrate through oil paint layers over time. Here is an excerpt from the document I cited above:
This has become a common misconception amongst artists that can be easily
explained. Most paints containing fatty acids (oils, alkyds, and egg tempera) can become more transparent as they age. The predominant effect is caused by the conversion of higher refractive index pigments (such as lead white,
zinc white, etc.) into soaps, stearates, and other complexes that have a lower refractive index, and therefore create a more transparent paint layer that eventually exposes the underlying paint layers or underdrawing. In oil
paintings, this is further compounded by a slight increase in refractive index that occurs in oil binders over time. This given the optical impression that an underdrawing (done in graphite, for example) is “migrating” to the surface
when in fact it is simply a natural chemical change that has occurred in the overlying paint layers. This phenomenon is also associated with the term “pentimenti,” as the increased transparency of the uppermost paint layers
can reveal earlier compositional changes and even unrelated paintings or sketches.
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