and pigment selection is extremely important for the serious artists because
the colors used in the works of art are subject to degradation. Some of the
great works of artists, such as Vincent van Gogh, are either fading, flaking, cracking,
chalking or darkening.
degradation, are comprised of synthetic pigments created in the mid-nineteenth
century. The brilliant chrome and cadmium colors, which were so popular during
the period of the Impressionists, Post-Impressionists and Fauvists, are not
lasting much longer than the artists, who painted them.
ensure that your paintings do not suffer the same fate, you need to carefully
select your paints and pigments. While Father Time may play some role in how
paint ages, other factors are more significant in the degradation process. These
factors include temperature, humidity, oxygen, carbon dioxide, sulfur dioxide
and light, both visible and ultraviolet. Degradation of color also occurs when
one pigment chemically reacts with another.
visible and ultraviolet light have enough energy to initiate chemical reactions
that affect pigments and the binding medium of paint. Exposure to ultraviolet light can
cause a variety of undesirable results. The resin is especially vulnerable. It can
become brittle and crack. It binding ability can degrade loosening its bond to
the pigment particles. This can develop into chalking in which loose pigment is
left on the surface of the paint after the binder has wasted away.
also affects pigments. The pigment particles absorb light and convert it into
heat. This heat can cause a chemical change in the pigment. In this chemical
reaction the pigment molecule can actually either gain or lose electrons, which
results in a color change. Colors can fade, yellow or darken. Inorganic pigments
are generally much less susceptible to photo degradation than organic pigments.
You should take this into consideration as you select either paints or
pigments.
fillers, which manufacturers often included in their formulations to lower
their raw material cost, have, in many cases, compounded the problem of
discoloration. In the age when artists ground their own pigments and made their own
paint, it usually consisted of just pigment and a resin, such as linseed oil. The
old masters usually did not add filler into their paint to extend coverage and
lower their costs. There are a few paint manufacturers, who still make paint the old
fashioned way without additives.
mechanisms of degradation, such as oxidation, change the chemistry of the
painted image. These chemical changes can alter the color of the paintings as well
as weaken the surface of the paint, resulting in flaking.
selection is one way to minimize degradation. Varnishing, which was practiced
by the old masters, can also provide protection by forming a barrier between
the atmosphere and the paint. These old timers must have been doing something
right. The paintings of the Renaissance have lasted for hundreds of years. That
leads me to believe that we should revive some of these old practices.
summary, the follow factors can effect degradation of paints and pigments:
light can degrade both the pigment and the resin binder.
humidity, oxidation, carbon dioxide and sulfur dioxide contribute to the
degradation process.
reactions between two different pigments can affect changes in color.
fillers can also contribute to problems of discoloration.
See my article Buying Artist's Oil Paints.
About Jim Hingst: After fourteen years as Business Development Manager at RTape, Jim Hingst retired. He was involved in many facets of the company’s business, including marketing, sales, product development and technical service.