What is "retarder"

Retarder \Re*tard"er\, n.

1. One who, or that which, retards.

2. (Steam Boiler) Any of various devices, as a helix of flat metal strip, introduced into a boiler tube to increase the heating effect of the fire.

3. (Photog.) A substance, as potassium bromide, added to a developer to retard its action.

1640s, agent noun from retard (v.). Of railway braking mechanisms from 1937.

n. Something which retards or slows.

Retarder may refer to:

• Retarder (album), an album by The Unband
• Retarder (chemistry), a chemical agent that slows down a chemical reaction
• Retarder (mechanical engineering), a device for slowing down large trucks, lorries, buses, coaches and other vehicles
• Retarder (railroad), a device to slow railroad freight cars as they are sorted into trains
• Acrylic retarder, a chemical agent added to fine art acrylic paint to slow its short drying time
• Dough retarder, a refrigerator used to slow down proofing of yeast when making dough
• Retardation plate, an optical device that alters the polarization state of a light wave traveling through it

A retarder is a chemical agent that slows down a chemical reaction. For example, retarders are used to slow the chemical hardening of plastic materials such as wallboard, concrete, and adhesives.

Sugar water acts as a retarder for the curing of concrete. It can be used to retard the chemical hardening of the surface, so that the top layer can be washed off to expose the underlying aggregate.

A retarder is a device used to augment or replace some of the functions of primary friction-based braking systems, usually on heavy vehicles. Retarders serve to slow vehicles, or maintain a steady speed while traveling down a hill, and help prevent the vehicle from "running away" by accelerating down the hill. They are not usually capable of bringing vehicles to a standstill, as their effectiveness diminishes as vehicle speed lowers. They are usually used as an additional "assistance" to slow vehicles, with the final braking done by a conventional friction braking system. As the friction brake will be used less, particularly at higher speeds, their service life is increased.

Friction-based braking systems are susceptible to " brake fade" when used extensively for continuous periods, which can be dangerous if braking performance drops below what is required to stop the vehicle – for instance if a truck or bus is descending a long decline. For this reason, such heavy vehicles are frequently fitted with a supplementary system that is not friction-based.

Retarders are not restricted to road motor vehicles, but may also be used in railway systems. The British prototype Advanced Passenger Train (APT) used hydraulic retarders to allow the high-speed train to stop in the same distance as standard lower speed trains, as a pure friction-based system was not viable.

Retarder is The Unband's first major label release.

In rail transport, a retarder is a device installed in a classification yard used to reduce the speed of freight cars as they are sorted into trains.