Glass - Iridescence or Mottling In Tempered Glass

Article No.
93-21-1

10/13/93

GLASS - "IRIDESCENCE" OR "MOTTLING" IN TEMPERED GLASS

FORD:
1984-94 CROWN VICTORIA, ESCORT, MUSTANG, TEMPO, THUNDERBIRD
1986-88 EXP
1986-94 TAURUS
1989-93 FESTIVA

LINCOLN-MERCURY:
1984-86 CAPRI
1984-87 LYNX
1984-92 MARK VII
1984-94 COUGAR, GRAND MARQUIS, TOPAZ, TOWN CAR
1986-94 SABLE
1988-89 TRACER
1988-94 CONTINENTAL
1991-94 CAPRI, TRACER
1993-94 MARK VIII

LIGHT TRUCK:
1984-90 BRONCO II
1984-94 ECONOLINE, F-150-350 SERIES, RANGER
1986-94 AEROSTAR
1991-94 EXPLORER
1993-94 VILLAGER

ISSUE:
Vehicles may exhibit iridescent spots or "mottling" in tempered glass under some lighting conditions. This condition is caused by the tempering process.

ACTION:
Explain to customers that "iridescence" or "mottling" of tempered glass is a normal condition and that glass replacement is neither warranted nor necessarily effective in resolving the condition.

DESCRIPTION OF CONDITION

The somewhat iridescent grayish or blueish and fairly geometric spots detected in side and rear window tempered glass are characteristic of tempered glass.

The mottled appearance is noted only under certain conditions of lighting. The occurrence of mottling does not affect glass quality or durability and cannot be reduced by scouring the glass surface.

The boldness of the mottled pattern in a given glass may vary, depending upon lighting conditions, but may appear intensified if viewed through polarized sunglasses.

CAUSES OF CONDITION

Atmospheric dust and other angular reflections can cause changes in the polarized properties of natural light. This polarization, combined with the light polarizing properties imparted to tempered glass by the forces of tension and compression (during the tempering process), cause the iridescent or mottled appearance.

These are the same forces of compression and tension which make tempered glass so remarkably strong. Windshields, which are annealed rather than tempered, do not exhibit iridescence.

OTHER APPLICABLE ARTICLES: 83-16-4
WARRANTY STATUS: INFORMATION ONLY
OASIS CODES: 102000