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How
is flat glass produced?
Most glass
today is produced by the float process. The raw materials (primarily
silica sand, soda ash, and limestone) are weighed, mixed and conveyed
to a melting furnace. Coloring agents may be added to produce
tints, such as green, blue, bronze, or grey. Molten glass flows
continuously from the furnace onto a bath of molten tin where
a continuous "ribbon" is formed. The glass floats on
the tin and is pulled and stretched to the desired thickness and
gradually cooled until it starts to solidify. The glass ribbon
is then lifted out of the tin bath onto rollers and conveyed through
an annealing lehr where the glass is slowly cooled until the glass
exits the lehr at slightly above room temperature. At this point,
the glass is flat and has virtually parallel surfaces. The continuous
ribbon is then cut to size, packaged, and shipped to the customer
for further processing.
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What
are the most common types of glass?
Flat glass,
as produced, is annealed. Annealed glass can be heat strengthened
or tempered to increase strength. Flat glass may also be laminated
to increase protection against fall-out and penetration of the
glazed opening. Lamination is a process where two or more pieces
(or lites) and one or more layers of plasticized polyvinyl butyral
(PVB) or another inner layer material are permanently bonded together
under heat and pressure. Rolled glass includes wired glass, patterned
glass, and art or stained glass.
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What types of glass does Zeledyne produce?
Zeledyne Float
Glass Operations is a primary float glass manufacturer. We supply
annealed float glass to our customer fabricators, who then perform
any fabrication of the glass as required (cutting of glass to
the proper size, heating treating, insulating glass, or laminating).
We manufacture
tinted glass in different colors (two shades of blue, two shades
of green, two shades of grey, and bronze). Two different reflective
coatings are applied to the colored substrates to produce five
blue products, five green products, three grey products, and two
bronze products.
Orientation
of the reflective coated surface in the finished state can provide
additional design options. A #1 surface (reflective coating out)
application results in increased reflectivity, and a crisp mirror-like
appearance. A more common usage is a #2 surface (reflective coating
in) application, which allows the base color to be more apparent,
and provides lower reflectivity.
Our customers
fabricate our glass into a variety of products such as windows,
curtain walls, doors, entryways, skylights, bath and shower enclosures,
interior partitions, shelving, tabletops, farm and construction
equipment, and car, truck, RV, and boat windows.
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What
is the difference between heat-strengthened and fully tempered glass?
Both processes
increase the strength of glass (tempered glass is about four times
as strong as annealed glass of the same thickness and configuration;
heat-strengthened glass is about twice as strong as annealed glass
of the same thickness and configuration).
NOTE: Heat-strengthening
glass does not change the stiffness of the glass and the amount
of deflection under load compared to annealed glass.
How do I determine
when to use heat-strengthened glass and when to use fully tempered
glass?
Fully tempered
glass is more commonly used in safety glazing applications since
its breakage pattern results in innumerable small fragments of
more or less cubicle-shaped pieces of glass which may vacate the
opening (Please check local code requirements for approval to
use fully tempered glass as a safety glazing material.).
Heat-strengthened
glass is used in areas where fully tempered breakage patterns
would not be desirable, such as in spandrel applications. Heat
strengthened glass has a breakage pattern similar to standard
annealed glass.
Heat-treating
may be necessary to address thermal stress concerns. For example:
It is recommended that Versalux™ Grey 2000 substrates be
heat treated (heat-strengthened or fully tempered).
It is recommended
that Versalux Blue 2000R, Versalux Green 2000R, and Versalux Green
2000T products be heat treated (heat-strengthened or fully tempered)
when the reflective coating is glazed towards the interior of
the building.
Versalux Blue
R, Versalux Green R, Versalux Grey R, Versalux Bronze R, and
Versalux Blue 2000T may require heat treating (heat-strengthened
or fully tempered) when the reflective coating is glazed towards
the interior of the building.
It is important
to note that, on occasion, even tempered glass can break spontaneously,
without any applied load, due to small inclusions that may be
present in all float glasses.
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What
is the standard specification for flat glass?
The standard
specification for flat glass is ASTM C-1036.
The standard specification for Heat-Treated Flat Glass is ASTM
C-1048
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Can
you assist me with writing a glass specification?
We would be
happy to assist you with the development of your glass specification.
Contact our Technical Services Department or the District Sales
Manager in your area.
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What
are your lead-times on shipments?
Most Zeledyne
Versalux products are readily available through our fabrication
customer base. Since our reflective products are pyrolytically
coated, they are typically in stock and can be fabricated, heat
treated, etc. at any time. If our fabrication customers do not
have the particular product in stock, we can typically ship an
order to them within 24 hours of receipt.
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What
is the difference between a hard coat and a soft coat?
A hard coat
is a pyrolytic coating applied on-line during the initial float
glass manufacturing process. Since the coating is applied while
the glass is still in a semi-molten state, it becomes part of
the glass.
A soft coat
is a sputtered process that is applied after the float glass has
been manufactured. The sputter coating is a surface coating and
does not become part of the glass.
There are
advantages and disadvantages to both types of coatings. Typically,
soft (i.e. sputter) coatings offer slightly better thermal performance
while hard (i.e. pyrolytic) coatings offer better durability.
Please contact your Zeledyne District Sales Manager for more information.
All Zeledyne
Versalux coated products (Versalux R, Versalux 2000R, Versalux
2000T) are pyrolytic coatings and can be cut, drilled, heat strengthened
or tempered, laminated, or made into insulating glass units without
damaging the reflective surface. This can pay off with reduced
lead times for both initial job requirements and future replacement
orders.
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What
is the best glass to use in warmer climates?
Glass with
a low shading coefficient or low solar heat gain coefficient is
preferred, rather than insulating (U or R) value, in areas where
average temperatures tend to be higher. Glass with a low shading
coefficient will help reduce the amount of heat gain into the
building structure, reducing cooling costs. Consult with your
window manufacturer to help you select a glazing package that
fits your location, application, and design options.
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What
is the best glass to use in colder climates?
In colder
climates, most regions get the best performance from a window
with a higher shading coefficient or higher solar heat gain coefficient.
This permits a higher amount of heat from the sun to enter the
building structure, reducing heating costs. Glass with a higher
insulating (U or R) value is preferred in areas where average
temperatures tend to be lower. Consult with your window manufacturer
or with our technical services department to help you select a
glazing package that fits your location, application, and design
options.
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What
is the Shading Coefficient?
Shading Coefficient
is the ratio of solar heat gain through a glass (or glass and
shading combination) compared to the solar heat gain of unshaded
1/8"(3.0 mm) clear float glass at normal incidence. The shading
coefficient of 1/8" clear glass is 1.0. Glazing that blocks
greater levels of solar energy have lower shading coefficients.
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What
is the Solar Heat Gain Coefficient?
Solar heat
gain coefficient is the solar heat gain through glass relative
to the incident solar radiation. The SHGC is similar to the SC,
but also accounts for absorbed, convected, and inwardly radiated
solar energy.
The Solar
Heat Gain Coefficient is approximately equal to 86% of the shading
coefficient.
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What
is Relative Heat Gain?
Relative Heat
Gain is the combination of solar heat gain (the transmitted energy
plus that amount of absorbed energy that is radiated to the interior)
and heat transfer due to the indoor/outdoor temperature differential.
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What
is Light Transmittance?
Light transmittance
is the ratio of the light transmitted to the interior of the structure
to the total incident light. The lower the light transmittance,
the less light is transmitted to the interior from outside. Low
light transmittance glass, such as Zeledyne Versalux Grey 2000,
Versalux R products, and Versalux 2000R products, is used where
privacy is of importance. Typical applications include interior
partitions and observation rooms as well as exterior applications
where increase privacy is desired.
With reflective coated glass, such as Versalux R, Versalux 2000R,
and Versalux 2000T, a #1 surface (reflective coating out) application
results in increased reflectivity, and a crisp mirror-like appearance.
A #2 surface (reflective coating in) application allows the base
color to be more apparent and provides lower reflectivity.
Note: There
will be a slight variation of performance characteristics as
well as differing glazing/cleaning requirements.
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The
glass seems to look like a "checker board" in some buildings.
What causes that?
Float glass
is produced by floating molten glass on molten tin. The surface
of the glass that contacts the tin ("tin surface") acquires
a very small amount of tin. As a result, this surface has a slightly
higher reflectance than the other surface ("air surface").
The difference is not perceptible with high light transmission
glass. With low light transmittance glass, such as Zeledyne Versalux
Grey 2000, the difference may be perceptible under certain lighting
conditions, resulting in the "checker board" appearance.
When low light transmitting tinted glass is fabricated and glazed,
it is important to maintain a consistent orientation of the surfaces
to prevent the "checker board" appearance.
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Does
a lower shading coefficient result in lower visible light transmittance?
The shading
coefficient represents the solar heat gain through the glazing
from the total solar energy spectrum. It does not have a direct
correlation to visible light transmittance. A good example of
this is Zeledyne Versalux Green 2000 High-Performance Tinted Float
Glass, which allows for a higher visible light transmittance and,
at the same time, a lower shading coefficient than a typical bronze
or grey tinted glass.
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What
is the Light to Solar Gain Ratio?
The Light
to Solar Gain Ratio (LSG) can be used to help select a glass product
when both high light transmittance and low solar gain are important.
The LSG is a glazing products Visible Light Transmittance divided
by the Solar Heat Gain Coefficient.
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What
can I do to reduce glare?
Glare has
a direct correlation to visible light transmittance. Lower visible
light transmittance results in less glare. Our most effective
products to control glare are our Zeledyne Versalux Grey 2000 substrates.
When using
glass with reflective coatings, a #1 surface (reflective coating
out) application results in increased reflectivity, and a crisp
mirror-like appearance. A #2 surface (reflective coating in) application,
which allows the base color to be more apparent, and provides
lower reflectivity.
Note: There
will be a slight variation of performance characteristics as
well as differing glazing/cleaning requirements.
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What are Spectrally Selective Glazing Products?
Spectrally
Selective Glazing Products have Visible Light Transmission of
>40% and LSG ratio of > 1.25 as outlined by the Federal
Energy Management Program.
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What
is low-e glass?
Heat energy
is comprised of long and short wave infrared radiation. Low-emissivity
coatings help reflect the long wave heat energy back towards its
source. The primary purpose of Low-E glass is to improve the insulating
value (u-value).
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What
is the difference between short wave and long wave infrared?
Short wave
infrared is what comes directly from the sun. It is converted
into heat when it comes in contact with an object. Long wave infrared,
as a result of solar energy, has started as short wave, but has
come in contact with an object and is now felt as heat. This is
what you see when you look at a hot object in the summer and you
see waves coming up from it (the short wave energy is being converted
to heat). Other sources of long wave energy include furnaces and
fireplaces.
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Is tinted glass with a low-e coating effective?
Tinted glass
is very effective when used in conjunction with low-e coatings.
This combination will reduce heat gain and may lower cooling costs.
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On which surface do you recommend applying a
Low-E coating?
In an insulated
glass unit, it can be applied to the #2 or the #3 surface; the
resulting winter u-value is the same with a slightly lower shading
coefficient if the coating is placed in the #2 position. In many
commercial applications, a tint or reflective product is required
which already allows for a lower shading coefficient. In this
case, installing the low-e coating in the #3 position is recommended.
An example
of this would be Zeledyne Versalux Blue 2000 High-Performance Tinted
Glass as the outboard lite, with an inboard lite of clear glass
with the Low-E coating on the #3 surface.
In residential
applications, a good rule of thumb to follow is to put the coating
on the #3 surface if heating bills exceed cooling bills, and on
the #2 surface if cooling bills exceed heating bills. If heating
and cooling costs are equal, the coating may be placed on either
surface.
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What
is ultraviolet (UV) light?
Solar energy
reaches the earth over a range of wavelengths. Ultraviolet light
or UV (300 to 380 nanometers) is short wavelength radiation. It
is invisible radiation and counts for approximately 2 percent
of the radiation reaching the earth.
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What are insulated glass units?
Insulated
glass (IG) units are two or more lites sealed together with a
space between them. The space contributes to the units insulating
ability by reducing the conduction of heat. IG units also offer
reduced sound transmission.
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What is used in the space between the two lites
of glass when an IGU is made?
IG units are
typically produced with a space filled with air, with one of the
inert gases, such as argon, to improve insulating factors, or
with sulfur hexaflouride, which enhances sound reduction.
What is "Safety Glazing"?
Safety Glazing
is glass that meets performance criteria that has been established
in order to reduce the risk of injury should someone fall into
it or through it.
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What are the U.S. standards for testing safety-glazing
materials?
ANSI Z97.1
and CPSC 16CFR, Part 1201.
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Where should Safety Glazing be used?
The locations
requiring safety glazing are prescribed by applicable building
codes. Some examples include doors, bath enclosures, and glazed
areas adjacent to passages. Safety glazing is generally required
for any glazed opening in a door through which a 3-inch sphere
may pass. For glazed areas adjacent to passages, the opening must
be safety glazed if the glazing is within 12 horizontal inches
of the opening.
Criteria for
the use of safety glazing differ in various regions, so you should
check local building codes to confirm the requirements for a given
installation.
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Are there special safety requirements in overhead
glazing?
Many building
codes mandate special considerations in overhead glazing. Tempered
glass is commonly used in residences. Laminated glass is commonly
used in commercial buildings. When tempered glass is used in commercial
structures the codes typically mandate screens be installed below
the glass.
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How is Safety Glass marked for identification?
A permanently
identifiable mark must be placed on all tempered glass used as
safety glazing.
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What is "Security Glazing"?
Security Glazing
is a glass product that can withstand a variety of threats such
as burglary, bullets, or some other form of physical attack.
How much does your glass cost?
Zeledyne Float
Glass Operations is a primary float glass manufacturer. We supply
our glass in a non-fabricated, non-assembled form to our fabricator
customer base, who then performs any fabrication of the glass
as required (cutting of glass to the proper size, heating treating,
insulating glass, or laminating).
If you are
interested in purchasing unfabricated float glass, contact your
Zeledyne District Sales Manager (See "Contact" for information).
If you are
interested in purchasing fabricated glass, we recommend contacting
a local fabricator or glazing contractor to assist you with any
budget information. Our District Sales Managers can refer you
to our fabricator customers in your area.
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What
is your recommendation for spandrel glass to minimize banding?
As a primary
float glass manufacturer, Zeledyne Glass Operations does
not fabricate typical spandrel glass. Spandrel panel applications
can be addressed in various ways: ceramic frits, polyester or
silicone based coatings, or without a coating in a shadow box
application.
In order to
minimize banding, one method would be to use a Zeledyne Versalux
reflective product on the outboard lite with the spandrel coating
on the #4 surface of the insulated unit.
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How
do I get samples of your glass products?
You can obtain
samples of Zeledyne Versalux products by contacting your Zeledyne
District Sales Manager (see "Contact Us" for information).
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How
can I best minimize glazing costs no matter what glass is selected?
Float glass
is produced in a continuous ribbon process with a standard width
of 130" in North American factories. Therefore, many standard
shipping sizes include one dimension of 130". If you design
your projects with awareness that maximizing the ribbon width
(130") results in greater utilization of production, higher
optimization can be realized and is usually figured into the cost
to produce the final product.
For example, a design requiring 50" in glass width will result
in two pieces of glass across the ribbon or 100" in total
- a 77% yield of the 130" dimension. A size that requires
69" in glass width may result in a single piece of glass
from the 130" dimension - a 53% yield of the 130" dimension.
The better the yield the lower the cost and the better chance
for you to maximize your return on glass investment.
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For further
assistance regarding this cost saving suggestion, please contact
your local fabricator, your glazing contractor, or your Zeledyne
District Sales Manager.
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