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Glass Industry Standards
Glass Industry Standards
Before pointing out defects and imperfections, understanding ASTM inspection criteria is very important. It outlines things such as inspection distance, lighting requirements, inspections times etc.
EXAMPLES OF VISUAL INSPECTION CRITERIA
- Glass shall be inspected in the central (see illustration and categories below) area in transmission at a distance of 5 feet from the observer, and in reflection at a distance of 10 feet from the observer.
- Glass shall be inspected in the border area in transmission and reflection at a distance of 10 ft from the observer.
- Glass must be inspected using a viewing angle of 90 degrees from the glass with suitable background light (daylight without direct sunlight or a range of 500 – 1000 foot lamberts.) If a lighting box is used as a light source, the diffusing plate shall be parallel to and at a distance of 10 ft from the glass.
- Inspection should not exceed viewing of more than 5 seconds for lites up to 6 square feet, 10 seconds for lites up to 35 sq ft, and 20 seconds for lites larger than 35 square feet, either in transmission or reflection.
- If defects are visible beyond what is allowable as listed by sizes (square feet) below using the inspection criteria, the glass may be rejected.
ASTM STANDARDS FOR GLASS: ALLOWABLE DEFECTS
a) Single (individual) lites up to 6 square feet.
- Scratches – Viewable as stated above must be 1” or less. No more than 1 is allowed per lite.
- Debris, Dirt, Spots – Viewable as stated above, must be 1/16” or less. No more than 1 is allowed per lite.
- Seeds, Bubbles, Knots, Stones – Viewable as stated above, must be 1/16” or less. No more than 1 is allowed per lite.
- No more than 1 total viewable defect as described above is allowed per lite.
- Shells – No more than ¼” from edge less than ½ the thickness of the lite. No more than 1 per side.
- Chips – No more than 1/8” from the edge. No more than 1 per side. (see illustration for chips.)
- Coating – Must be uniform on the lite inspected when viewed in transmission using the inspection criteria previously stated above.
- The border area is comprised of 2 inches plus ½” from each edge of the lite. All other area is the central area (see illustration.)
b) Single (individual) lites 6 to 35 square feet.
- Scratches – Viewable as stated above must be 1” or less. No more than 2 are allowed per lite and must be separated by a minimum of 24 inches.
- Debris, Dirt, Spots – Viewable as stated above, must be 1/16” or less. No more than 2 are allowed per lite and must be separated by a minimum of 24 inches.
- Seeds, Bubbles, Knots, Stones – Viewable as stated above, must be 1/16” or less. No more than 2 are allowed per lite and must be separated by a minimum of 24 inches.
- No more than 2 total viewable defects as described above are allowed per lite.
- Shells – No more than ¼” from edge less than ½ the thickness of the lite. No more than 1 per side.
- Chips – No more than 1/8” from the edge. No more than 1 per side. (see illustration for chips.)
- Coating – Must be uniform on the lite inspected when viewed in transmission using the inspection criteria previously stated above.
- The border area is comprised of 4 inches plus ½” from each edge of the lite. All other area is the central area (see illustration.)
c) Single (individual) lites over 35 square feet.
- Scratches – Viewable as stated above, must be 1” or less. No more than 3 are allowed per lite and must be separated by a minimum of 24 inches.
- Debris, Dirt, Spots – Viewable as stated above, must be 1/16” or less. No more than 3 are allowed per lite and must be separated by a minimum of 24 inches.
- Seeds, Bubbles, Knots, Stones – Viewable as stated above, must be 1/16” or less. No more than 3 are allowed per lite and must be separated by a minimum of 24 inches.
- No more than 3 total viewable defects as described above are allowed per lite.
- Shells – No more than ¼” from edge less than ½ the thickness of the lite. No more than 1 per side.
- Chips – No more than 1/8” from the edge. No more than 1 per side. (see illustration for chips.)
- Coating – Must be uniform on the lite inspected when viewed in transmission using the inspection criteria previously stated above.
- The border area is comprised of 6 inches plus ½” from each edge of the lite. All other area is the central area
Glass Inspection for the Homeowner
The glass industry has developed consensus standards/specifications that address quality aspects of various types of glass used in windows, doors and skylights. These standards are very comprehensive and typically written for manufacturers who have expertise in applying them. The standards are also very specific to a given glass type. These types include raw flat (annealed) glass, heat-treated glass (ex. tempered), coated glass (ex. low-E), laminated glass and IGUs. Unfortunately, the methods of inspection and the blemish or issue criteria are not always the same for each type of glass.
In most cases, a homeowner will have a window, door or skylight that contains an IGU that is comprised of two or more panes of flat glass. Typically, this glass will also have some type of low-E coating. If there is a safety concern or a code requirement for safety glazing, the window may also contain tempered or laminated glass. With a combination of all these glass types in one window, door or skylight, sorting out the appropriate criteria to the respective standard is at best a complicated, if not confusing, endeavor. How then is a homeowner to know whether an issue or blemish is a legitimate concern?
The following is a general guideline offered to simplify the inspection of glass issues for the homeowner. This is not necessarily a definitive guide covering all glass related concerns; that’s the job of the industry standards. Rather, this guideline is a check for a homeowner to flag whether an issue merits consideration for replacement.
Home Inspection Directions
~ Thoroughly clean the glass on both sides with glass cleaner.
~ Stand 10 feet away, directly in front of the glass (90° to the surface).
~ The glass should be illuminated with daylight, but not direct sun.
~ If an issue or blemish is readily apparent, measure the size of the blemish.
~ Contact the Blueline Glass if the blemish is noticeable and is outside the following limits.
For more information on glass and glazing industry standards please visit the following site for more information:
https://fgiaonline.org/pages/glass-inspection-for-the-homeowner