pigmented colorants: dependence on media and time - Cornell ...
pigmented colorants: dependence on media and time - Cornell ...
pigmented colorants: dependence on media and time - Cornell ...
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<strong>on</strong>d together to form proteins. Examples of important proteins include keratin<br />
(found in skin, wool <strong>and</strong> feathers), hemoglobin <strong>and</strong> silk.<br />
In the c<strong>on</strong>text of traditi<strong>on</strong>al binding materials, glue refers specifically to a<br />
substance derived from boiling skins or c<strong>on</strong>nective tissues of certain mammals or<br />
fish. The adhesive is the protein collagen, which is a major structural ingredient<br />
in mammals <strong>and</strong> fish. Skin glue is made from the extracted gelatin from boiled<br />
raw hides, <strong>and</strong> is sold in powder form or as plates.<br />
The protein has the unusual property of being soluble in hot water, but gels<br />
as the soluti<strong>on</strong> cools to room temperature. If substance is left, the water will<br />
completely evaporate <strong>and</strong> the substance will harden. Hence, a painter using this<br />
<strong>media</strong> must work while the glue is hot. Glue paint is made fresh daily, as reheated<br />
glue loses some of its binding strength. The method of painting with a soluti<strong>on</strong> of<br />
gelatin <strong>and</strong> water is called distemper. A comm<strong>on</strong> artists’ glue paint is extracted<br />
from rabbit skin, which yields a very str<strong>on</strong>g, matte, <strong>and</strong> colorful paint film. The<br />
most attractive quality of the glue paints is its beautiful reflecti<strong>on</strong> of light due<br />
to the grains of pigment that are lying <strong>on</strong> the top of the paint layer. Of all the<br />
binding <strong>media</strong>, glue is almost certainly the <strong>on</strong>e mostly widely utilized around the<br />
world, though from different animal sources.<br />
An emulsi<strong>on</strong> is a stable mixture of an aqueous liquid with a oily, fatty, waxy or<br />
resinous substance. The yolks of hen’s eggs c<strong>on</strong>tain albumen (a gummy substance),<br />
a n<strong>on</strong>drying oil, <strong>and</strong> lecithin (an efficient, stabilizing lipoid). Yolk is approximately<br />
<strong>on</strong>e-third protein, the rest c<strong>on</strong>taining oil droplets in water. Albumen bel<strong>on</strong>gs to<br />
a class of proteins that have the property of being coagulated by heat, as dem<strong>on</strong>-<br />
strated by a cooked egg. The same effect occurs when it is spread out in a thin<br />
film <strong>and</strong> exposed to daylight. Tempera painting refers to a binder of egg yolk.<br />
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