Colour media is the blanket term for material which is placed into a light beam in order to tint, or colour-correct it. Other related products that do not colour the light beam, but do alter it, are also included under the term "Colour Media".
The most popular form is the flexible, transparent
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Colouring the Stage: In earlier times, colour was imparted to stage productions during the day by holding them at different times outdoors so as to take advantage of, and make use of, naturally lit conditions. Warmer colours occur at the start and end of daylight. Brighter ones are seen in the middle of the day, especially under a cloudless sky. To contrast, cloudy skies presented muted colours and a softer, diffused ambience.
In the Dark: At night or indoors, candles or torches were typically used, although fireplaces and bonfires would not have been out of the question. Any could impart upon a performance much warmer tones, and induce a heightened contrast against a night sky if outside. Under a full moon though, one could additionally produce a contrast between cold moonlight and warm open-flame sources.
Tinting the Light: A way of altering the colour of light at night or when inside was through the use of dyed, translucent scarves or handkerchiefs. Despite the hazard of fire, they would be suspended near the open-flame light source so as to impart colour. A safer way was to put a coloured liquid such as red wine into a glass and place it near a light source.
Imparting Emotion: Colour served a purpose for a mostly illiterate audience. How? By choosing a colour for a scene to match its emotion, it helped the less literate to understand at least the general gist of a play.
Colours Might Represent:
These were not used universally, but give an idea of how an entire audience, regardless of pedigree or education, might enjoy and understand a performance, and thus be more likely to atend. This is little different from today where commerciality must be a viable goal for any organisation or performance business -- regardless of how extreme its productions become.
Surprisingly from our technological vantage point, a creative
person centuries ago was actually able to light a performance,
but shone even more skilfully by taking advantage of some or
most of the above. Even the changing alignment of the stars,
moon and planets could conceivably have been incorporated
for late evening, night, or early morning shows.
Glass Enters: At some point, coloured glass began to be used to tint light. It had been noticed that depending on the ingredients used in the making process, the result was a tint to the glass. So then glass makers included various chemical compounds so as to purposely colour the glass. The stained glass method that came to be used in churches for hundreds of years was adapted for the stage. This was safer than using coloured fabrics, but the glass would eventually smoke over and would have to be cleaned or replaced from time to time.
Later Artificial Sources: In subsequent centuries, coal-oil, kerosene, and gas lamps were used as light sources until the time of lime burning and electric light. These were placed between reflectors and lenses to provide a focused beam. Lime was the first really brilliant artificial light source used for theatre. Its incandescence was created by directing a jet of flaming oxyhydrogen gas on to a block of lime, wherby a very bright, white light was produced. Finally, in the late 1800s, a viable electric lamp was developed which became popular in the theatre because it was the least likely of all to produce a fire.
Light created by both lime and electric sources was also directed with reflectors and lenses. The lenses protected to a better extent the fabrics and glasses used to tint the light source... but superior colouring materials were to come about in the 1900s.
Once non-flame light sources were invented, tinted glass was the most common colouring agent for theatrical purposes. However, as the chemical industry developed, non-glass substitutes came to be. They became popular due to their low cost, low weight, greater colour selection, and their ease of cutting. These `plastic' media were not as fragile as glass -- at least initially in their service lives.
This was one of the first `plastic' synthetic colour media devised. Made in Germany in the early 1900s, it used gelatin (yes, the same as you might eat for dessert). Gelatin is easily dyed and rolled into sheets. When dry, it forms a transparent, coloured sheet that is suitable for stage lighting in non-wet locations and using low-wattage fixtures.
The advantages to this type are low cost and a resistance to scratching. (Scratches seem to almost fill in, with this type of colour media.) However, it absorbs moisture and will actually dissolve in water. As well, it becomes brittle after being subjected to stage light beams, and if roughly handled, it will tear starting almost from after its first usage. It is OK for permanent installations where the gel is to be left untouched after being placed, but it cannot stand up well to the abuse of touring.
Gelatin was eventually manufactured by a number of companies. It had a good range of colours available but has now fallen into disuse because better materials have emerged that are waterproof and can stand higher heat. There is no known manufacturer currently producing the gelatin colour medium.
Developed after World War II, acetate, a cellulose based material, was the original waterproof, plastic colour media. It is capable of withstanding temperatures of around 100 C, is tougher than Gelatin, and as said, is not soluable in water. However, it's prone to fading, and if subjected to multiple high-heat/cool cycles becomes brittle and will tear or shatter. It scratches easily, as well. The colour range is at least as good as Gelatin. As is with gelatin, there is likely no manufacturer currently making an acetate colour medium.
PVC was a short-lived alternative to acetate that came out in the 1950s. It is no longer made. No details regarding colour range or durability are available at this time.
Here was the next material successfully used. It can withstand temperatures of 200 C, is waterproof, and is resistant to fading in all but the hottest fixtures. This matarial never becomes brittle with use, so it had a much longer service life than the above two. Polyester was the colour medium that saw the theatrical colour range expand greatly so that today, there are hundreds of shades available.
The latest of the plastic colour media materials, it is very strong, fade resistant, and can handle temperatures around 400 C. Colour range compares with that of the Polyester medium.
Polycarbonate crinkles and can become brittle after prolonged exposure to high heat. However, it remains much more robust in this condition unlike Gelatin, which when it became brittle, tore easily. Polycarbonate can be broken in this condition, but it takes more effort. If handled carefully, one can continue to use the gel until it becomes too dark to be usable. (Unlike Acetate and Polyester colours which lighten with usage, Polycarbonate filters actually darken during their service life.)
As mentioned, coloured glass had been around for centuries, but after the coming of electric light and gelatin, it saw only limited stage usage except in border lights and some low to medium wattage fixtures. Today, it may still be found, but these uses have been mostly supplanted by plastic colour media, and now by coloured LEDs which require no filters because they emit light at given wavelengths, thus actually shining in a given colour.
However, one major location seen now is in moving beam and colour-changer fixtures in the form of the dichroic glass filter. This uses heat-resistant glass that has a thin coating which diffracts the light into pure colours in much the way as does a rainbow or as is seen in an oil slick on water. This results in very narrow-range colour with a high transmittance factor. These filters are available outside of moving beam/light usage but have not proven popular due to their high cost, proneness to breakage, and their limited colour selection compared to plastic colour media.
On a related subject, another instructional
available at this website discusses
Primary and Secondary Colours.
Here is the AIEL Purchase Guide's
Colour Media Table,
a summary chart of the types just discussed.
You can obtain a Swatch Book
of the Polyester and Polycarbonate ranges.
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