Editing Color gel (section)

== History ==
In [[Shakespeare]]an-era theater, [[red wine]] was used in a glass container as a light filter. In later days, colored water or [[silk]] was used to filter light in the theater. Later, a [[gelatin]] base became the material of choice. Gelatin gel was available at least until 1979. The name ''gel'' has continued to be used to the present day. Gelatin-based color media had no melting point, and the color was cast in the media as opposed to being coated on the surface. It would, however, [[charring|char]] at high temperatures and become brittle once heated, so that it could not be handled once used in the lighting instrument.

By 1945, more heat-tolerant and self-extinguishing [[polyvinyl acetate|acetate]]-based through-dyed materials were being manufactured (marketed as Chromoid then Cinemoid by Strand Electric). In the U.S., Roscolene (acetate) was developed to deal with higher output light sources. Though cheaper, the acetate filters eventually fell out of favor with professional organizations since they could not withstand the higher temperatures produced by the [[tungsten halogen lamp]]s that came into widespread use in the late 1960s. 

The acetate-based material was replaced by [[polycarbonates]] like Roscolar ([[mylar]] polycarbonate) and [[polyester]]-based filters. These materials have superior heat tolerance. Polyester having the highest melting point of {{convert|480|F}}. 

Often a surface coating was applied on a transparent film. The first dyed polyester gels were introduced by Berkey Colortran in 1969 as Gelatran, the original deep-dyed polyester.<ref>{{Cite web|url=http://www.derekleffew.com/gelhistory|title=Gel history|website=www.derekleffew.com|access-date=2019-03-22}}</ref> The Gelatran process is still used today to produce GAMColor (100% of the line) and Roscolux (about 30% of the line).<ref>{{Cite web|url=https://ca.rosco.com/en/product/gamcolorr|title=GAMcolor|website=ca.rosco.com|access-date=2019-03-22}}</ref> Other color manufacturers, such as [[Lee Filters]] and Apollo Design Technology, use a surface applied dye. (Roscolux is 70% polycarbonate and 30% deep-dyed polyester.)

Almost every color manufacturer today uses either polycarbonate or polyester to manufacture their gels. Even today's gels can burn out (to lighten in color starting in the center) easily, rendering them useless. As instrument design improves, it has become a selling point on many lights to have as little heat radiating from the front of the fixture as possible to prevent burn-through, and keep stage equipment and actors cooler.

[[File:MotorisedColouredGel.jpg|thumb|A motorized color gel]]

In the 1930s, Strand Electric of [[London]] provided the first numbering system for their swatches and with their agents in [[New York City|New York]] and [[Sydney]], the numbering system went round the world. Remnants of this original filter color system exist in the color swatches of today (such as Deep Amber = No.&nbsp;3; Primary Red = No.&nbsp;6; Middle Rose = No.&nbsp;10; Peacock Blue = No.&nbsp;15; Primary Blue = No.&nbsp;20; Primary Green = No.&nbsp;39). 

In the theater, gels are typically available in single {{cvt|20|x|24|in|mm|-2}} sheets, which are then cut down to the appropriate size before use. The size originates from the gelatin days: it is the same as a standard baker's sheet, which was used to cast the sheets. In the film industry, gels are usually cut straight from rolls {{cvt|24|or|48|in|mm|-2}} wide and {{cvt|50|ft|m|0}} long, as the size required may vary from a single practical halogen spotlight in a ceiling to a whole window.