Front Surface Mirror Aluminum Mirror No. 756
Specification No. 1058

Spectrophotometric curve shown in the visible region is measured at normal incidence.

*When the coated element is used at angles other than normal, curve peaks will shift toward shorter wave lengths (down scale). This variation is dependent on degree of angularity from normal incidence.

Reflectivity
The mirror shall have not less than 94% total reflectivity for light in the visible region as measured with a Weston photronic cell with a Viscor filter and a tungsten lamp supplying light at an angle of incidence of 22.5°.

Adherence
No visible part of the mirror coating shall be removed by the cellulose tape test described here:

Test: The tacky surface of cellulose tape shall be carefully placed in contact with a portion of the mirror surface and firmly rubbed against that surface. It shall then be quickly removed with a snap action with exerts the greatest possible stripping action on the mirror film.

Note: During the above test, care should be exercised to prevent contaminating abrasives contacting the coated surface causing slight sleeks.

Corrosion Resistance
There shall be no noticeable deterioration of the finished mirror when given the salt atmosphere test described here:

Test: The mirror shall be placed in a thermostatically controlled cabinet with a salt atmosphere for 24 continuous hours at a temperature or 95° F. The salt atmosphere shall be obtained by allowing a stream of air to bubble through a salt solution containing 1 1/2 pounds of sodium chloride per cubic foot of water.

Effect of Temperature
The coating shall function satisfactorily and shall not be damaged by exposure to an ambient temperature of minus 60° F and plus 500° F.

Hardness
No evidence of film removal or film abrasion shall be visible to the eye when the following test is applied:

Test: A pad of clean dry cheese cloth (previously laundered) 3/8 inch in diameter, 1/2 inch thick, bearing with a force of one pound on the coating shall be rubbed across the coated element in any direction 200 times.