pigmented colorants: dependence on media and time - Cornell ...

tion of paint tubes in 1841 and the development of the paint industry in subsequent
centuries, artists became separated from the paint manufacturing process. Unfor-
tunately, most artists lost the motivation to understand the details of the trade.
While artists became freer in the creative process–manufactured tubed paint al-
lowed them to leave the studio to work–the diminishing knowledge of materials
led to serious negative effects. The use of inadequate and incompatible materials,
poorly tested paints, and the experimentation of paint formulas without knowledge
of possible consequences led to disastrous effects on the longevity of paintings.
2.2.1 Pigment
There are two distinct types of <strong>colorants</strong>: dyes and pigments. Colored substances
that dissolve in liquids and impart their colored effects to materials by staining
or being absorbed are classified as dyes. Individual dye molecules are only five
to ten times that size of a water molecule. The water molecules firmly attach to
each dye molecule, allowing the result to swim freely in the water. Because of
their small size, dyes dissolve in, bond with, or absorb into the material they come
into contact with. These bonds are not easily undone and therefore the resulting
color cannot be modified much after being applied to a surface. For most painterly
works, the paint surface is reworked considerably; hence dyes are not suitable for
most artistic work as they are very immediate <strong>colorants</strong>.
Instead, artists use pigments, or small insoluble colorant crystals. For example,
a pigment that occurs naturally is the deep red colorant Hematite, comprised
mostly of ferric oxide. In addition, the dyes that are used in painting must first be
laked–bonded chemically to a transparent, inert metallic base which transform the
dye into an insoluble pigment. For example, a historic laked dye is formed from the
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