Hi,
I recently came across a very insightfull book by Max Doerner.
In the book he mentions that the strength and archival longevity of ancient paintings can also be attributed to the fact that the pigments were ground much more course,providuing a greater adhesion of the pigments to the oils resulting in a very durable paint film in contrast to what we have in modern times,that modern colormen risk creating very weak oil paints by grinding the pigments too finely in their persuit of color brilliance andsmooth paint consistency.Though it can be rectified somewhat by adding finely ground pumice stone or marble dust to give the paint film some grit.
On the surface this makes sense to me in many ways but would like to hear your opinion on this matter.
Thank you.
Unfortunately, Doerner had many incorrect ideas about the materials and techniques of the Old Masters. The most egregious was his belief in their use of very complex oil/tempera mixtures and the heavy reliance on incorporating soft resins into their paint.
His thoughts on pigment particle size are more interesting, although I believe that is probably a little over simplistic. Particle size, shape, and hetro/homo-geneity plays a major role in paint rheology, color saturation, surface gloss, and especially hiding power. The fine art painter generally does not want all of their paints to have the same optical effect. Some are better when opaque and other transparent. Additionally, there are many examples where old master paintings have suffered due to the overly coarse mature of a particular pigment. An obvious example is the unfortunate darkening of azurite and ultramarine paint layers. Often (not always, but that is a separate issue) these paints are darkened due to old degraded varnish that has been imbibed and ingrained into the sand paper-like surface where it could not be removed without abrading away the paint layer.
I am not sure whether a paint layer of the same pigment would fare better if the pigments were more coarsely ground (for instance very finely ground yellow ochre versus coarsely ground yellow ochre). The following paper on the role of pigment particle size in modern industrial paints suggest the opposite. They clearly state that reducing pigment particle size improves paint films.
https://www.pfonline.com/articles/the-importance-of-particle-size-in-liquid-coatings
It did only focus on modern coatings and completely ignores some of the aesthetic aspects of paint used in fine art. For instance, light plays differently off a paint composed of coarser particles, especially lean paint films without a varnish.
Perhaps some of the other moderators can add to this.
Regarding the “cement/aggregate” or “brick and mortar” concepts of paint integrity, regardless of particle size, uniform dispersion of the pigment within the binder is extremely important, and obviously, roller mills do a very good job at that.
Many manufactured pigments today start out with a much smaller particle size and greater uniformity than those produced by earlier processes, so milling doesn’t always have as important a role in reducing particle size as in the past. There are exceptions, however, including genuine Viridian, which often has visible grains in the finished paint.
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