Most mirrors are going to look fantastic right out of the factory. But how well will they hold up after five, 10, 15 or 25 years of exposure to weather, harsh temperature changes, water, and natural sunlight experienced during outdoor use in the elements? Testing is as important as good manufacturing — and tests must be rigorous if a mirror is going to endure the harsh realities of the planet’s mean streak. In order to guarantee durability, manufacturers should employ at least two tests.

Corrosion Protection: Salt-Fog Testing

In the salt-fog test, mirrors are put into a testing chamber, where they are exposed to a hot, moist, foggy spray of salt water with a fairly neutral pH. This mist completely covers every part of the mirror’s surface for several hours at a time. Customers require most manufacturers to test for between 200 and 500 hours. But to ensure exceptional dependability it is better to test for closer to 1,000 to 2,000 hours. If one mirror has a high quality-protection system and another mirror uses lower quality materials, a 2,000 hour exposure test will usually demonstrate the difference.

Ultraviolet Light Test

The ultraviolet light exposure test, or QUV test, attempts to recreate the harsh rays of the sun and weather to see how well the mirror will hold up — and for how long. In order to simulate 20 to 25 years of real-life exposure, the intensity of the light must be much higher than that which is found in nature (unless you have two decades to kill while waiting for the results). If UV exposure is ten times higher intensity than that which is found than nature for instance, the acceleration effect on yellowing will be of a similar magnitude. Furthermore in the QUV test, the specimens are heated and cooled and periodically exposed to water mist. The combined effect of heat, water absorption and desorption, and UV light is much more detrimental to mirrors than the individual effect of either water exposure or UV exposure alone. This acceleration affect helps gauge the mirror’s durability over extended periods of time.

The elements are hard on plastics with outdoor applications, and many mirrors can’t stand the test of time. Inferior mirrors cost less, but are far more likely to need to be replaced after fairly limited exposure. The highest-quality plastics are literally expected to last a lifetime.