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October 1996 issue of R&D Magazine Pages 25-26 below is a condensed version of this article
Two basic types of testing are available: long term, real-time testing outdoors and accelerated artificial weathering both indoors and outdoors. South Florida Test Service (a Miami FL division of Atlas) provides real time sites at Miami FL and Whitman Arizona for subtropical and desert test conditions. The article has a photo of the main test site in Miami where nearly a million samples are tested daily. They also have smaller facilities for high altitude exposure (Prescott AZ), temperate climates with light industrial pollution (Chicago IL and Cedar Knolls NJ), temperate climate with acid rain (Louisville KY), and high moisture (Seattle).
Outdoor weathering usually involves mounting products or test specimens on racks at fixed angles to the sun. The samples are evaluated at regular intervals. Indirect weathering (used to test color fastness and durability of indoor materials) involves exposing the materials under glass.
Real time testing takes a great deal of time. Accelerated weathering is an attempt to reduce this time. Usually the test is specifically trying to find the damage caused by long term exposure to sunlight. Sunlight is a major cause of damage to plastics, textiles, paints, and other organic materials according to a spokesman from Q-Panel Company in Cleveland. Accelerated testing uses a variety of light sources to simulated sunlight and the damage it causes.
Fresnel-reflecting solar-concentrator mirror systems are commonly used. Atlas has a machine called the EMMAQA that tracks the sun with its target board. This speeds up environmental testing up to 8 times. Several artificial lights have been tried in the past but they are expensive. Now fluorescent ultraviolet lights mimic the short UV wavelengths that cause the main damage to most materials. Some of the lights actually cause certain materials to fail that are "ok" in outdoor testing. The most reliable means of simulation is filtered xenon-arc lamps. Atlas also manufactures these. They can be programmed for light - dark cycles, temperature and humidity, water spray, dew, and irradiance control and can hold more than 100 samples at once.
Next to sunlight, humidity is the major concern. Environmental testing usually involves relative humidity, while industrial testing involves absolute humidities. Panametrics in Waltham MA manufactures a line of humidity sensors based on capacitive solid state sensors. Blue M Electric in Watertown WI manufactures ultra-low humidity, cascade humidity, and steady state chambers.
The story also includes a photo of some output from Universal Software a program from Hunter Lab of Reston VA that displays, analyzes, and reports color-measurement results for paints, foods, plastics, textiles, and paper. It includes statistical process requirements and spreadsheet-type data displays.
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