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

which linseed oil derives (the most commonly-used oil in oil painting). Linen is
much more expensive and less commonly used in modern times.
It is universally considered that cotton is an inferior material to linen can-
vas. Cotton fibers are quite short and resistant to stretching. They suffer rapid
degradation when subjected to atmospheric stresses, especially when the fabric is
stretched tightly (as in painting). Individual linen fibers are considerably longer
than those of cotton, thus the material is somewhat more durable and has a livelier
feel when it is stretched over a frame. The higher volatility of cotton can result in
cracking and damage to the paint layer. In addition, cotton fibers show a measur-
able color change after relatively little exposure to light. Despite these facts, many
artists–unaware of the technical issues of archival painting–continue to use cotton
duck canvas, mainly because it is so much less expensive. Overall, the best canvas
is closely woven pure linen with the threads of warp and woof equal in weight and
strength.
Figure 2.3: Left: magnified view of the interweaving threads of a cotton
canvas. Right: further magnification shows the fibers comprising
each thread. The average thread width for this canvas is approximately
575µm and the fibers are approximately 12µm in width
Flexible supports are stretched over a wooden frame (stretcher) to provide a
suitable surface to work using tacks or staples. An artist does this carefully to
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