In optical filters and theatrical lighting a color gel is a transparent or translucent colored panel used to change the color of transmitted light.

A gel (from the lat. gelu—freezing, cold, ice or gelatus—frozen, immobile) is an apparently solid, jelly-like material formed from a colloidal solution. By weight, gels are mostly liquid, yet they behave like solids. An example is gelatin.

Many gels display thixotropy - they become fluid when agitated, but resolidify when resting.

By replacing the liquid with gas it is possible to prepare aerogels, materials with exceptional properties like very low density, very high surface area, and excellent thermal insulation properties.

In 2005 a sound induced gelation effect was demonstrated.

Applications

Many substances can form gels when a suitable thickener or gelling agent is added to their formula. This approach is common in manufacture of wide range of products, from foods to paints, adhesives. Gels are a mixture of a solid and a liquid.

In fiber-optic communications, a gel resembling petroleum jelly in viscosity is used to surround a fiber, or multiple fibers, enclosed in a loose buffer tube. This gel serves to lubricate and support the fibers in the buffer tube. It also prevents water intrusion if the buffer tube is breached. Gels are also used in fiber-optics as index-matching materials. Source: from Federal Standard 1037C and from the FAA Glossary of Optical Communications Terms

The classification of gels and jellies: Classifications:

1 - inorganic or organic

2 - water as the liquid component are hydrogels; organic solvent as liquid are organogels

3 - colloidal or coarse (size of the particles which form the framework)

4 - rigid gels, elastic jellies, and thixotropic gels (mechanical properties)

See also

• Hair gel
• Xerogel
• Silica gel
• Gel electrophoresis, Agarose gel electrophoresis, 2-D electrophoresis, SDS-PAGE
• Gel filtration chromatography, Gel permeation chromatography

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