Gel

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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 Latin gelu "freezing, cold, ice" or gelatus "frozen, immobile") is a colloidal system in which a porous network of interconnected nanoparticles spans the volume of a liquid medium. In general, gels are apparently solid, jelly-like materials. Both by weight and volume, gels are mostly liquid in composition and thus exhibit densities similar to liquids, however have the structural coherence of a solid. An example of a common gel is edible 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 including very low density, high specific surface areas, and excellent thermal insulation properties.

In 2005 a sound induced gelation effect was demonstrated.

[edit] 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.

In fiber optics communications, a soft gel resembling "hair gel" in viscosity is used to fill the plastic tubes containing the fibers. The main purpose of the gel is to prevent water intrusion if the buffer tube is breached, but the gel also buffers the fibers against mechanical damage when the tube is bent around corners during installation, or flexed. Additionally, the gel acts as a processing aid when the cable is being constructed, keeping the fibers central whist the tube material is extruded around it.

Gels are an important part of chemistry, and can be used to form solids.

The classification of gels and jellies: Gels can be loosely classified along the following lines:

1 - Either inorganic or organic in nature

2 - Having water (hydrogels), or an organic solvent (organogels) as the liquid component

3 - Being either colloidal or coarse in nature (size of the particles which form the framework)

4 - As a rigid gels, elastic jellies, and gels