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As further information to Wayne's discussion, let me add that in the manufacturing
of tinted windshields with a tint band, it is not the glass that is actually
tinted at the top but is the laminate polyvinyl butyrate, otherwise known
as PVB.
This material is what contains the colored tint band and is sandwiched
between the two matched formed layers of glass. This sandwich is then placed
in a vacuum chamber, slightly heated and evacuated which removes any bubbles
or voids in the transparent laminate and fully bonds all three pieces together.
Excess PVB is trimmed from the outer perimeter and the windshield is then
ready for installation.
Differing from the laminated windshield is the method used for tint
bands on a backlite. Since the backlite is tempered, any area tinting adding
to the coloring of the glass itself must be done with a coating on the
interior surface of the glass. This is usually accomplished using an Electron
Beam chamber, which is first evacuated and then filled with an inert gas.
The charged E-Beam is then aimed at a target material such as stainless
steel, gold, silver or other metal. When the beam hits the target
it vaporizes. The vaporized material is then deposited on the glass. Masks
and other methods are used to direct the vapor to a specific area on the
glass if the entire surface is not to be tinted.
Most "clear" glass will actually filter out 5% of the incoming ambient
light and a very small per centage of UV. Federal regs limit the amount
of tinting to glass to about 35% so that vision is not restricted.
However today, additional UV protection can be provided with transparent
additives to the glass and/or the coating material so that almost all UV
can be stopped. The techniques work well on tempered glass with or without
a color tinting and actually reflect IR and most of the harmful UV rays
away from the interior. The process is expensive but it works.
Brian
D500s in MI
Wayne Graefen wrote:
Several
points to note on this subject.Solex
(tinted) glass was introduced in the US auto industry during the 1951 and
1952 model years. It was a separate option not tied to air conditioning
and was just slightly higher in price than clear glass. You could
order just the windshield tinted or you could order all glass tinted.
For almost all cars a shaded (darker upper band) windshield was also available.
Some cars some years, such as '57-61 tall back window Mopars also offered
a shaded back glass with a silver tint so back seat passengers did not
sunburn their necks. As
late as 1957 when a Mopar was ordered with air conditioning, there was
no factory requirement that tinted glass also be ordered. I own a
needs-restored '57 Chrysler 300C convertible that the factory build sheet
shows was built with clear glass all windows and factory air conditioning.I
recall corresponding with someone authoritative that it was 1958 when Mopar
started automatically packaging full Solex tinted glass with the air conditioning
option.After
a decade or so, safety experts determined that looking through green tinted
glass at red/yellow/green intersection stop lights (particularly those
hung overhead) was distorting the colors of the lights so about 1961 (I'm
unsure exactly) the glass industry changed the color of the Solex tint
to blue and it remains that way to this day including all reproduction
windshields for '50s cars.The
green Solex was particularly prone to fading and the blue is too but far
less so. If your car came with tinted glass, in the logo (or "bug")
area of the glass it states "Solex". Solex is a registered trademark.Hope
this helps.Wayne
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