GLASS THICKNESS & AIR SPACE MEASUREMENT: IG UNITS
GLASS THICKNESS MEASUREMENT (LITE #1)
The bottom scale (Reference point “A”) is used for measuring the glass thickness while
the top scale (Reference point “B”) is used for measuring the air space. Please note
that the scales are different. DO NOT attempt to use the wrong scale for your measure-
ment. The best method of measurement is to work your way through the IG assembly.
In other words, measure the thickness of lite #1 first, then read the air space, and finally
read the thickness of lite #2. To begin, verify that reflection 1 is aligned with your “zero
point”. Reflection 1 represents the top surface of the first piece of glass, while reflection
2 represents the bottom of the first piece of glass. Once the zero point is aligned, you
can take your measurement. The distance between reflection 1 and 2 is the thickness
of the first lite of glass, as measured on the GLASS THICKNESS scale. The example
shows a glass thickness of approximately 7/32”. Regarding the ASTM standards indi-
cator, please note this falls into the acceptable range for 1/4” glass thickness.
AIR SPACE MEASUREMENT
To measure the air space, slide the entire slide assembly scale to the left and align reflec-
tion 2 with the zero point. Once aligned, you can now measure the air space thickness
using the top scale. Reflection 3 represents the top surface of the second lite of glass.
The distance between reflection 2 and 3 represents the air space, as indicated on the
AIR SPACE THICKNESS scale. The example shows an air space of approximately 1/2
inch.
WARNING!
For the most accurate measurement of air space thickness, the operator should take
readings near the edge of the IG assembly. Be aware that many IG units may sag inward
or bow outward due to air pressure differences inside the window as opposed to the
outside atmospheric pressure. If a window deflects inward or outward, the air space
thickness in the center of the IG unit will differ from the thickness near the edge. The
least amount of deflection will occur near the edges of the glass near the spacer bar.
Please note, this is also a great method to check IG units for deflection in production
as well as in the field.
GLASS THICKNESS MEASUREMENT (LITE #2)
To measure the glass thickness of the second lite of glass, slide the entire slide assembly
to the left again, so that the “zero point” is lined up with reflection 3. Reflection 4 rep-
resents the bottom surface of the second lite of glass. The distance between reflection
3 and 4 is the glass thickness of the second lite of glass. Be sure to use the “GLASS
THICKNESS” scale when measuring glass thickness.
OVERALL IG UNIT THICKNESS MEASUREMENT
To use the Overall IG Unit Thickness scales, the operator must first verify the glass
thickness that is in the IG unit. To test this, the operator may use the glass and air
space thickness scale, or use the ASTM standards indicator which is located on both
the top and bottom of the Overall IG Unit Thickness scales. To use this, simply align the
zero point as described previously. Using the ASTM indicators, measure the thickness
of both lites of glass in the IG assembly. To use the overall thickness scales, both lites
of glass must be in the same thickness designation. In other words, if you have an IG
assembly with a 3/16” pane for lite 1 and a 1/4” pane for lite 2, you CAN NOT use this
scale. Both lites must be the same thickness.
To measure the overall IG unit thickness, align the zero point. Verify that the glass
thickness of the IG unit matches the scale you have installed on the gauge slide. Using
the correct thickness scale, measure the distance between reflection 1 and reflection
4. This is the overall IG unit thickness for the assembly being tested.
The example above illustrates an IG unit constructed of 1/4” lites of glass. The overall
thickness of the IG unit is 31/32”, as measured on the OVERALL IG UNIT THICKNESS
scale for 1/4” glass.
APPLICATIONS
This gauge has been successfully tested on a variety of glass combinations. The follow-
ing list includes the various types of glass that have been tested successfully: Single
pane float glass, IG units (double, triple & quadruple glaze++), clear, Low-E, tempered,
reflective, bronzed, tinted, laminated, bullet-proof, mirrors, plus others. The following
explanations define the most common applications.
Single Pane Float Glass & IG Units
See “Glass Thickness & Air Space Measurement: IG units”.
Triple Glazed IG Units
Triple glazed IG units are measured in the same manner as the double
glazed IG units. The only difference will be two extra laser reflections.
These two extra reflections represent the third lite of glass. The distance
between reflection 4 and 5 is the second air space (between lite 2 and lite
3), as measured on the Air Space Scale. The distance between reflection 5
and 6 corresponds to the glass thickness of lite 3. Be sure to use the Glass
Thickness scale for this measurement.
Laminated Glass & Bullet Resistant Glass
Bullet resistant and laminated glass are measured in like manners. Use only
the Glass Thickness scale for these measurements. A faint laser reflection
will occur at each laminate substrate. This allows you to measure the thick-
ness of each piece of glass in the laminated assembly, as well as the over-
all thickness of the laminated assembly. The distance between reflection 1
and 2 is the thickness of pane 1. The distance between 2 and 3 is the thick-
ness of pane 2. The distance between 3 and 4 represents the thickness of
pane 3. The distance between reflection 1 and 4 will yield the overall thick-
ness of the laminated assembly. All of these measurements use the Glass
Thickness Scale. The illustration shows two pieces of 1/4” glass laminated
on both sides of a 1/2” piece of glass. The overall thickness of the lami-
nated assembly is 1”. If the regular scale does not show the laminate inner-
layers, you can switch to the scale labeled “FOR LAMINATED OR BRIGHT
REFLECTION NUMBERS
REFLECTION NUMBERS
2
