Common Glass FAQs
- 1. How is glass made?
1. How is glass made?
Almost all glass produced today in the developed countries is done so by the “float process”. The glass composition materials, mainly silica sand, soda ash and limestone, are melted in a furnace and then flowed on to a bath of molten tin. The glass is formed and gradually cools as it moves from the tin bath to an annealing lehr, which is a controlled cooling chamber. As it moves through this process, the glass is in the form of a continuous ribbon, which is cut to size and packaged at the final stage.
- 2. What are the most common types of glass?
2. What are the most common types of glass?
All float glass as it is initially made in the above description is called annealed and is the most common. Float glass is made in a variety of colors or tints, in addition to basic clear glass. Annealed glass, the starting point can be further fabricated in many ways. Coatings of various types can be applied to achieve many visual effects and affect the optical properties. In addition the glass can be heat treated to increase its strength and give it safety glazing properties. Glass can be put into an insulating glass unit, meaning two or more pieces of glass are separated by a dry air space to improve the insulating properties.
- 3. What is the best glass product for the sunbelt areas of the country?
3. What is the best glass product for the sunbelt areas of the country?
Proper window design in the south must account for solar heat gain in order to help reduce air-conditioning. Therefore glass products should have a low solar heat gain coefficient or low shading coefficient; the u-value, or insulating performance is of lesser importance.
- 4. What is the difference between long wave and short wave infrared?
4. What is the difference between long wave and short wave infrared?
- Short wave infrared energy comes directly from the sun but is not felt as heat. It converts into heat when it strikes something.
- Long wave infrared is the heat radiated from an object which has received short wave radiation, for example, a hot automobile dashboard or a hot sidewalk or roadway where you can often see heat radiating from the surface.
- 5. What are the Shading Coefficient and the Solar Heat Gain Coefficient?
5. What are the Shading Coefficient and the Solar Heat Gain Coefficient?
These terms are mathematically related and both describe the solar energy blocked from passing through a glass material. The shading coefficient is the ratio of solar energy that passes through a piece of glass relative to piece of 1/8” clear glass (which has a shading coefficient of 1.0). Solar heat gain coefficient represents the solar gain through the glass relative to the incident solar radiation; it is equal to 86% of the shading coefficient. In either case, a lower number indicates improved solar control over the 1/8” clear glass baseline.
- 6. What is better, a high or low shading coefficient?
6. What is better, a high or low shading coefficient?
In colder, heating-dominated climates such as Canada or northern US, windows with higher shading coefficients generally are preferred and conserve energy. This is because in the longer heating season, more solar radiation, which becomes “free” heat is allowed to pass into a home.
In the south, with a long air-conditioning season, it is most important to reduce solar gain and therefore reduce air conditioning loads.
- 7. Does long wave infrared energy only come from the sun?
7. Does long wave infrared energy only come from the sun?
Any heat source, such as furnace or engine which consumes and combusts fossil fuel, release long wave energy. Any object, like a sidewalk or road or windowsill, which has been exposed to short wave solar radiation will also emit long wave infrared energy. Therefore, the sun is not responsible for long-wave infrared energy; it provides short-wave solar radiation.
Safety Glass FAQs
- 1. What is safety glazing?
1. What is safety glazing?
Glass is a breakable material, which when broken into smaller sharp pieces often called shards can cause serious injury. Safety glazing material, usually tempered glass or laminated glass, reduces the risk of injury. This is accomplished in the case of tempered by the characteristic break pattern-many small pieces, and by the adhesion of the glass pieces to the inner plastic layer in the case of laminated glass.
- 2. What is security glazing?
2. What is security glazing?
Security glazing products usually involve multiple layers of glass, and in some cases acrylics, usually laminated, in order to achieve maximum impact resistance from explosions, ballistic assaults and even simple forced entry. There is a wide range of such specialty glass products.
- 3. What are the U.S. Standards for testing safety glazing materials?
3. What are the U.S. Standards for testing safety glazing materials?
ANSI Z97.1 and CPSC 16CFR, Part 1201.
- 4. Where should safety glazing be used?
4. Where should safety glazing be used?
The Federal safety glazing law stipulates that safety glazing be used in architectural applications ( homes and buildings ) in defined hazardous locations. Generally the hazardous locations include doors, immediately adjacent sidelites, bath and shower enclosures and glazing adjacent to passages where there are walking surfaces adjacent to the glass and the bottom edge of the glass is within 18” of the floor. In addition to the Federal law, various local code authoritites have additional requirements.
- 5. Are there special safety glazing requirements in overhead glazing?
5. Are there special safety glazing requirements in overhead glazing?
Many local building codes mandate special considerations for overhead glazing. It is common to require and use tempered glass in residential overhead applications. Laminated, often heat-treated glass is commonly required in commercial building applications. Often, when tempered glass is allowed in commercial building, some form of restraining screening is also required below the glass.
- 6. How is safety glazing marked for identification?
6. How is safety glazing marked for identification?
The Federal safety glazing law requires that all safety glazing products have a permanently identifiable marking on each piece. This marking cannot be removed without damaging or breaking the glass and is generally located in one of the corners of each piece.
Low-E Glass FAQs
- 1. Can you use PPG Low-E glass in a single-glazed window?
1. Can you use PPG Low-E glass in a single-glazed window?
Sungate® 400 coated glass and Solarban® 60, Solarban® 67, Solarban® 70XL, Solarban® 72, Solarban® Z50, and Solarban® R100 coated glasses must be used only as a component of a sealed insulating glass unit.
In addition, all Low-E coated glasses yield their best energy performing characteristics when used in a sealed insulating glass units.
- 2. Is it better to have the coating on the #2 or #3 surface of an insulating glass unit?
2. Is it better to have the coating on the #2 or #3 surface of an insulating glass unit?
The answer to this question is really dependent on the specific design conditions of your application. The light transmittance and the U-value of the unit will be the same whether the coating is on the #2 or #3 surface; however, the Solar Heat Gain Coefficient will be lower when the coating is on the #2 surface.
In general, if you are concerned about reducing solar heat gain (typically in a cooling climate), then using the coating on the #2 surface would best meet the requirement. On the other hand, if you are interested in utilizing passive solar heat gain (typically in a heating climate), then using the coating on the #3 surface would best meet the requirement.-
- 3. What are the differences between PPG Low-E coated glass products?
3. What are the differences between PPG Low-E coated glass products?
PPG manufactures a variety of low-e coated glasses using two different manufacturing processes. The following table identifies the PPG product and associated manufacturing process.
PPG Low-E Coated Glass Products Product Manufacturing Process SUNGATE 400 Coated Glass MSVD SOLARBAN Z50 Coated Glass MSVD SOLARBAN 60 Coated Glass MSVD SOLARBAN 67 Coated Glass MSVD SOLARBAN 70XL Coated Glass MSVD SOLARBAN 72 Coated Glass MSVD SOLARBAN R100 Coated Glass MSVD
In the Pyrolytic manufacturing process, the coating is applied to the glass ribbon while it is being produced on the float line and the coating then “fuses” to the hot glass surface. The glass is then cut into stock sheets of various sizes for shipment to fabricators. For pyrolytic coatings, Sungate® 500 and 600 coatings are very durable, both mechanically and chemically. And, while Sungate 500 and 600 coated glasses offers reduced emissivity and some solar control, they do not perform quite as good as PPG’s MSVD.
In the MSVD (Magnetic Sputtering Vapor Deposition) process, the coating is applied to pre-cut glass (usually in stock sheets for further fabrication) in a vacuum chamber at ambient plant temperatures. MSVD coatings such as Sungate® 400 and Solarban® 60 Low-E glasses offer lower emissivity and superior solar control versus pyrolytic. However, MSVD coatings are not as durable as pyrolytic coatings, either mechanically or chemically, and must always be used as a component of an insulating glass unit with the coating located within the sealed airspace.
- 4. Do all Low-E coated glasses look the same?
4. Do all Low-E coated glasses look the same?
No, they do not. Color differences between various low-e coatings are due to the use of different coating materials, the thickness of the various coating layers, as well as differences in manufacturing processes.
- 5. Can tinted glass be used with Low-E glass?
5. Can tinted glass be used with Low-E glass?
Yes it can. Tinted glass can be used as the outdoor lite in an insulating glass unit, with PPG Low-E as the indoor lite. The low-e coated glass improves the insulating properties of the insulating glass unit, while the tinted glass reduces the influx of solar energy through the insulating unit.
- 6. How effective is tinted glass with PPG Low-E coatings?
6. How effective is tinted glass with PPG Low-E coatings?
- Tinted glass is very effective when used in conjunction with PPG Low-E glass. This combination will reduce excess heat gain and lower cooling costs.
- The tinted glass reduces the amount of excess heat gained on east, west, and south exposures
- Tinted glass can provide improved glare control, if needed.
Glass Staining and Cleaning
Glass is generally resistant to chemical attack and other degradation. It is inert to most acids, except hydrofluoric and phosphoric.
Typical glass problems on buildings would be:
• Alkalis leaching from concrete, mortar, plaster and gravel onto glass can cause staining and etching
• Hard water, high in calcium concentrates, which are allowed to continually run on the glass
• Deterioration of labels and protective films when left on the glass for prolonged periods
• Pitting of the glass, mainly due to weld splatter (in the form of black specs on the glass), improper sandblasting on site or wind blown debris
• Abrasions to the glass surface by using harsh, powder based cleaning products• Scratches or spalling caused by the
improper removal of plaster, paint, varnish or mortar splash
• A white staining effect which occurs when condensation repeatedly forms and dries on the glass, which in turn can cause surface decomposition
• Iridescence or the oil-stain image is a direct result of the wet-dry action of condensation or water on, or between the glass(es)
The only practical remedy for glass that is badly damaged by scratches, weld splatter, sandblasting, etching and even damaged edges is full replacement.
For cleaning purposes use a soft, clean grit-free cloth and water with a mild detergent. Thoroughly wash off any detergent residue with clean water. Do not under any circumstances use any form of abrasive cleaner as this may cause damage to the glass. Do not allow any metal or hard parts of squeegees or other cleaning equipment to contact the glass surface. Metal scrapers should not be used. Special care should be taken when cleaning coated reflective surfaces.
Care and Storage
Glass quality can be maintained and risk of damage minimised by following some simple guidelines in storing and handling. Storage areas should be clean and dry with a good circulation of cool dry air, particularly after periods of high humidity to avoid wet-dry staining. Interleaving material should be used at all times, if possible with ‘lucite’ or ‘colacryl’, which contains adipic acid which acts as a stain inhibitor.
Store glass on even surfaces in areas not subject to heavy traffic or overhead debris. Where glass has been received in a wet condition, it should be unpacked, dried and re- stacked with separators that allow airflow between the panels.
Glass should always be stacked at an incline of 4 degrees from the vertical. Thick glass, tinted glass, insulated glass (IG) units and reflective glass should be stored out of direct sunlight to avoid any risk of thermal breakage. IG units must not be rotated or ‘cartwheeled’ over their corners.
Always use clean dry suction cups and do not use glass with severely vented or damaged edges.