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PYROLYTIC
OR VACUUM COATED GLASS?
There are two types of reflective glass available,
pyrolytic and vacuum coated:
Pyrolytic -
a coating is applied during glass manufacture. The
coating is fused into the glass at 1200degC. The
advantage of this product is its durability. It can
be handled like a standard square of glass. It is
ready to be cut, heat strengthened and toughened.
This product is sometimes called a ‘hard coat’ reflective;
Vacuum
coated glass - involves the deposition of metal
particles on the glass surface by a chain reaction
in a vacuum vessel. It is often called a ‘soft
coat’, because the coating is more susceptible
to damage than a hard coat glass when glazed in
monolithic form. Where toughening of the product
is required, the product must be toughened first
and then vacuum coated. Vacuum coated glass is
available in laminated form with the coating on
the inside, protected from damage. Subject to certain
exceptions, vacumn coated products have better
shading co-efficient values than pyrolytic products.
DID YOU KNOW?
 all
reflective glass absorbs and reflects a greater
amount of heat than normal tinted float and therefore
is more prone to thermal breakage. Ask our technical
department for a FREE thermal assessment;
toughening
or heat strengthening will prevent thermal
breakage;
all
vacuum coatings on tinted float glass must be heat strengthened
or toughened as a minimum;
before
glazing, annealed glass edges must be ‘good’ straight
and clean cut with minimal defects. Laminated glass should
have flat ground edges on all sides as a minimum. Under
no circumstances should reflective glass be glazed with
damaged edges;
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under
no circumstances can abrasive cleaner be used on any
surface;
spandrel
panels must always be heat strengthened;
some
building authorities/local councils
set limits on excessive glass reflectivity of around 20%. Most monolithic
products should be glazed with the reflective surface to the inside or
surface (2). This will only marginally decrease performance, but will enhance
the colour of the glass avoiding the strong ‘mirror’ like appearance
when viewed from the outside. Subject to certain exceptions, the coated
surfaces in laminated glass are on surface (3), which enhances the colour
of the interlayer used;
avoid use
of vacuum coated monolithic reflective in entry doors because of coating
susceptibility to damage;
toughening
and heat strengthening of reflective glass will create some
roller
wave or visual distortion.
It is recommended that a mock-up unit or on-site installation be viewed;
it is recommended
that where tempering is required to avoid thermal breakage, heat strengthening
is the option where glass is glazed above ground level. Where the relevant
glazing code requires toughened safety glass, it should only be used when
the glass, upon breakage, is unlikely to ‘shower’ down to the
ground. The alternative is to use a heat strengthened laminated glass which
complies with human impact codes and will stay intact upon breakage. |
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