lunes, 29 de abril de 2013

No fog systems for glass

A glass fogs when humid air is in contact with its cold surface. It causes the water vapor (which is in the air) being condensed on the glass surface.

There are different sites where we can get a frosted glass. Windows, the windshield of the car, refrigerators, or the bathroom mirrors are some examples.

To fix or prevent this situation there are different solutions according the needs of each sector.  These solutions range from double glaze unit, coated low e glass, thermal printing screens on the surface of glass or laminated glass using a PVB specially designed to prevent fog, and others.
  • Double glaze unit: Consists of an insulating glazing formed from two or more sheets of glass separated by dehydrated air camera.  With this composition, you can get an excellent thermal and also acoustic insulation glass, and you can also remove the “cold wall” effect. That reduces the possibility of condensation on surface glass.

  •   Coated Low e glass:  It is a glass which its surface has been treated by a metallic treatment (the glass do not lose  its appearance and transparency). With this treatment the glass reflects the thermal radiation which it reduces the possibility of condensation on it surface

            There are two types of treatments or coating:
    • Hard coat
    • Soft coat

The differences  between both can be found in the method which were manufactured and its effectiveness.
The hard coat glass is less effective in terms of "reflect thermal radiation" that the soft layer. In opposite, the hard layer is a higher security glass because you can tempered (hard ended), while the soft coat glass can not be tempered. Meanwhile, the soft coated glass treatment needs to be employed in a double glazing unit which the face treated has to be inside the camera because if not the coated side can be rust. That does not happens on the hard coated glass.
For that reasons, the soft coated glass is used on construction applied on windows to get the maximum efficiency, and the hard coated glass is used on industry market applied on refrigerator, buffet exhibitors, where the security is very important.
  • Thermal silkscreen applied on glass surface. Using an enamel paint which melts into the glass during the tempering process and it creates an electric circuit that generates heat.  That heat makes warm the surface glass, therefore it avoid having condensation of water vapor. To  generate these heat, that glass must be connected to a power source.
This glass is used in the automotive industry for their high efficiency (applied on vehicle rear window). It Is a kind of glass which is also used in areas where the temperature difference between glass and ambient air is very high. For example it is used for the fingers doors at the Nordic airports

  • Thermal laminated glass. Is a safety glazing composed of two or more sheets of glass unit by one or more layers of a plastic called polyvinyl butyral (PVB). This plastic has a very good qualities of elasticity, transparency and impact resistance.

In contrast to other laminated glass, in that case, this PVB has been developed specifically to do not get fog.
It is a PVB that you connected to the current to generate heat on all surface glass as the thermal silkscreen solution do it,  to prevent water vapor be deposited in the glass surface  and fogging it.

With that “no fog” laminated glass, it is no necessary any kind of silkscreen, thereby we avoid having lines on glass surface and we get almost a perfect viewing through it. With that kind of composition it is possible to produce a tempered and laminated glass to get an optimal security.

This glass can be used in many applications, as well as the front and back side of cars,  in doors, windows, refrigerators,  the windshield of boats, etc.

  • Others.  We can find  other no fog solutions. For example there is an adhesive sheets that allow heating the glass surface to prevent this fogging. The only drawback of this system is that these sheet makes opaque the surface of glass. For this reason, this system is usually used in a bathroom mirrors, where the sheet is located at the back of the mirror and connected to the current.

Thereby, depending  on the application you need you can choose the most suitable system.

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