It is the nature of float glass to contain natural defects or imperfections. Some unacceptable and some acceptable. As a purchaser of float glass we follow the same criteria and expect the same quality from our glass supplier, as would any purchaser of our sealed units.
Sunrise Windows & Door Depot Ltd. glass quality control criteria is based on the Canadian General Standards Boards for Flat, Clear float glass and our suppliers industry standard for Low E and SunStop glazings.
An ellipse or circle having axes equal to 80% of the height and width dimensions of the glass panel. This allows a fairly large area at the corners that may have imperfections not allowed in the central area.
The remaining area of the glass to within 9mm (3/8") of the edge.
The 9mm (3/8") border around the perimeter of the glass panel that is covered in glazing. Any flaw that does not adversely affect the strength or function of the glass panel is permitted in this area.
Inspection will be done by looking through glass and perpendicular to it, using daylight without direct sunlight or with background light suitable for observing each type of defect. Distance to inspect should be 1m (3') away for Gaseous inclusions, Stones, Knots, Digs, Strings, and waves. For Scratches, Rubs and Crush the distance is proportional to the intensity of the fault.
How long can a Scratch be?
If it is not a dig greater than 1.5 mm and depending on the intensity of the scratch, it cannot be seen at the distance indicated in the Standard Inspection Method then any length is acceptable. Should the scratch be medium intensity, 1" long and only 1/2" of the scratch is seen from 10" then it is rejected. A light scratch that is 12" and cannot be seen from 10' away is acceptable.
How many imperfections allowed per sealed unit?
The maximum allowable is 3 providing all three imperfections conform to the above chart.
Why is dust in between the glass and so much of it?
With direct sunlight, dust is amplified to a degree where it looks as if the sealed unit is filled with it. Sunrise Windows has a state of the art clean room to minimize the amount of dust present while manufacturing sealed units. However even under these conditions, there will always be a certain amount of dust in between the glass. Over time these particles will fall down to the bottom of the sealed unit as the static charge reduces the attraction of the dust to the glass.
If there is a hair or fingerprint between the glass, is that acceptable?
No. A hair or fingerprint within the Central or Outer Area is not acceptable. However a fingerprint within the Border Area is acceptable as this will not affect the performance characteristics of the sealed unit and will not be seen after glazing.
There are some small particles and fibers between the glass. Is this acceptable?
If the particles and fibers are faint and small enough that they cannot be seen from 3' away in normal lighting (no direct sunlight), then this is acceptable. After washing, glass exhibits enough static to attract small particles, dust and fibers from the air and onto the glass. It is unavoidable. These particles will over time lose this static charge and will fall to the bottom of the sealed unit. This is acceptable, as these particles will not affect the performance of the sealed unit.
Bubbles - Includes: Gaseous inclusions, Open gaseous inclusions, seeds and stones. These refer to round or oval shaped bubbles, generally 1-2 mm wide that may contain small particles such as rock or sand used in the productions of float glass. There is a depression in the glass that accompanies the inclusion or seed that will be apparent when looking at it from an angle. They are an inherent defect in the best quality of plate glass.
Crush - A lightly pitted area resulting in a dull gray appearance over the region.
Digs - Deep, short scratches.
Rubs - Abrasion of the glass surfaces producing a frosted appearance. A rub differs from a scratch in having more width.
Scratches - Any marking or tearing of the surface appearing as though it had been done by either a sharp or rough instrument. Scratches occur on glass in all degrees from various accidental causes.
Distance - Intensity
Faint 8" - Visible only to the trained eye
Light 3' - Just noticeable
Medium 10' - Visible as a slight grayish haze
Heavy 10' - Readily visible as a cloudy surface
Strings - Wavy, transparent lines appearing as though a thread of glass had been incorporated into the sheet.
Wave - Defects resulting from irregularities of the surfaces of glass making object viewed at varying angles appear wavy or bent.
Note: If more information is required - detailed Spec's Information sheets, from the Glass Manufacturer can be provided upon request.
Scratches - Vision Glazing: Scratches visible at 3 meters (10 ft.) which are up to 75 mm (3") in length shall be acceptable. Scratches over 75 mm (3") in length shall be acceptable if within 75 mm (3") of the edges of a lite, or are not within the normal viewing area.
Pinholes - Vision Glazing: Pinholes visible at 3 meters (10 ft.) which are up to 1.6 mm (1/16th) in diameter shall be acceptable. Large clusters, or close spacing of pinholes, visible at 3 meters (10 ft.) shall not be acceptable if within the normal viewing area.
General - Vision Glazing: Any other defects in the vision area that are not readily visible at 3 meters (10 ft.) shall be acceptable. Any imperfections in the coating within 10 mm (3/8") of the edge of a lite shall be acceptable.
Causes - Window glass can crack when a mechanical force is applied to it. Cracking can also occur by a thermal force, which is caused by a large difference in temperature between one part of the window and another.
Mechanical forces may be wind, flexing of the window frame due to house settling or excessive construction / hammering close to the window. Glass by its nature is not homogeneous product as such. It is not stable under stress from temperature changes.
Thermal stress is created by a temperature difference between the center of the glass and the edge. Normally, a temperature difference of 30 degrees Celsius is needed to cause cracking. Many environmental factors can cause such a temperature variation, for example:
- a cold night followed by a bright sunny morning will heat up the center of the glass very quickly
- Shadows on the glass created by roof overhangs, landscaping or other buildings
- Internally applied film of coating on the window
- Reflective or light colored Venetian blinds closed during the hottest point of the day
The above types of cracks are extremely hard to predict and cause is practically impossible to determine. As such, the glass industry does not provide a warranty to cover this type of window cracking.
Indoors Shading - Venetian blinds, draperies or other shading fixtures must be hung to provide space on the sides and bottom, or top and bottom to allow air movement by natural convection. Failure to do so will result in excessive thermal stress, which can cause cracking, which is not covered under warranty.
The following are recommended to avoid this situation:
- a minimum of 40mm (1-1/2") clearance should be left on the top and bottom of the shading fixture, or on the sides and bottom
- a minimum of 50mm (2") clearance should be left between the glass surface and the shading fixture
- any heating or air conditioning outlets should be located on the room side of the shading fixture
- vertical blinds are preferred over drapes or horizontal blinds, open weave draperies are preferred over tightly knit material
To offset the lack of adequate ventilation, tempered glass may be needed. Application of solar film on the glass inside the home will cause thermal stress, which is not covered under warranty.