To get the most out of the functionality and quality of our glass, there are certain things you need to know. The Norwegian Glass og Fasadeforeningen (association for glazing and façades) provides information that will ensure you gain the full and lasting benefit of your products.
Condensation / dew may occur on the inside of your windows. This is most normally caused by:
- Excessive air humidity indoors
- Poor ventilation (particularly in new buildings)
- Low indoors temperature
- Deep bay windows
- Double glazing with high (poor) U-value
Condensation / dew between the glass in double glazing
- Caused by a crack in the edge seal.
Condensation / dew on the outside of the glass
High-quality double glazing with low U-value (according to requirements in building regulations) provides a low level of heat loss through the glass. As a result, the outer pane may have a temperature that is lower than dew point. In special weather conditions, this may result in dew or condensation on the window exterior.
Crack caused by external impact
An impact, blow or vibrations can cause glass to crack.
Crack caused by settling damage
Changes in a building’s structure caused by movements in the foundations or building can cause glass to crack.
Cracks caused by temperature differences on the surface – thermal cracks
Thermal cracks caused by critical temperature differences on the surface of the glass can be caused by:
- Having some parts of the glass surface covered
- Having exterior blinds partly lowered
- Interior fittings (curtains/blinds/shades) fitted close to the glass with poor ventilation
- Interior fittings (curtains/blinds/shades) covering only parts of the glass
- Foil/labels applied to parts of the glass surface
- Objects placed against the glass surface (insulation, cushions etc.)
- Furniture pushed up against the glass
- Heating devices used close to glass represent a risk. Deflection and pressure cracks in double glazing.
Deflection and pressure cracks in double glazing
Double glazing is made up of two or more panes of glass separated by spacers. The spacers are glued in place using a two-step seal to the surface of the glass along the edges, forming an air-tight gap (spacing). Fluctuating air pressure and temperatures, in addition to altitude, will have an impact on concave and convex curvature of the double glazing (deflection). Major differences in air pressure outside the double glazing in relation to the air pressure in the gap between the panes can apply such a high impact that cracks appear in the seal or even in the glass. When assembling double glazing at altitudes exceeding 750 metres above sea level, the glass will be subject to major differences in air pressure.
Scratches on the glass
- Glass has a hard surface, but can be scratched and damaged if exposed to hard, sharp objects.
- Please note that tempered glass has a surface that is more exposed to scratches than non-tempered glass.
- Metal scrapers must NOT be used on glass.
- The first time you clean windows etc. after the building stage is completed, always use plenty of water.
- If there are glue or paint residues etc. on the glass, take care when removing these as you may scratch the glass.
- Normal window cleaning requires plenty of water, cloths and a rubber blade (squeegee).
- Make sure that you only use cleaning agents that are suitable for the glass surface.
- Remove labels on new glass by soaking them with water and wiping off with a soft cloth.
- Label residues or other impurities on the glass surface can be removed by carefully using a ceramic cleaning agent for cooker tops.
- Please note that metal cleaning tools must NEVER be used.
Run-off from concrete and brick, and from air with a chemical content
- Can corrode the glass surface so that it becomes dull. This type of damage can, in certain circumstances, be polished off using suitable tools.
- If you would like more detailed information, please contact the Norwegian Glass og Fasadeforeningen (association for glazing and façades).
Welding splashes and sparks
- Burn fast to the glass and damage the surface.
- This type of damage to glass cannot be repaired without causing lasting damage/optical effect on the glass.
Impurities in the glass
- Glass is a natural product made up of sand, sodium carbonate and lime. Impurities that look like small dots in the glass cannot be avoided. The permitted size of these dots and their number are defined in international standards.
Roller wave distortion
- During the hardening process, roller waves may appear in the glass. Such roller wave distortion is permitted within defined limits specified in international standards.
- Brewster’s fringes appear as irregular, rainbow-coloured marks in double glazing. They are difficult to see and are normally only seen in a reflection. These fringes characteristically “wander” if you press lightly on the glass.
- Newton’s rings appear as rainbow-coloured rings in the centre of double glazing. These occur when the panes in double glazing touch or are close to touching each other.
Iridescence / anisotropy
- The visual effect is a shimmer of colour with hints of a dark coloured ribbon or wave patterns in the glass.
- According to standard NS-EN 12150-1 for thermally toughened glass, iridescence in toughened glass is a physical effect and cannot be classified as a visual fault.
- Iridescence occurs more commonly in thicker glass, from 8 mm and up, and more so if the glass surface has a reflective coating.
Colour nuances in glass
- As glass contains iron oxide, it will always have a hint of green colour that is increasingly evident the thicker the glass. Glass can be produced with a reduced iron oxide content – often referred to as low-iron glass – and will have a clearer and purer colour with less green.
- Glass manufactured by one company but in a different production series may also have different nuances of colour.
- The same applies to the same type of glass made by different manufacturers.
Colour nuances in surface coatings
- Just as glass may have different nuances of colour, surface coatings may also have different colours. The angle of viewing and weather conditions have an impact on how these are seen.