Gel is slang for
gelatine, now common called simply
color. It is/was used to
color theatre lights. Gelatine is very
brittle,
vulnerable to
heat and
humidity, and
fades quickly. It was common to use a
pounce wheel to punch a series of
holes to facilitate
air flow to help
cool the gel to prevent
burn out. Gel has been replaced in the past couple decades by synthetics such as polyester. These synthetics tend to be more robust, and are less sensitive to heat and humidity. Most
theatre electricians use a
grease pencil to mark the
manufacturers number on the gel, as there are over 1000 different colors. See also
gel