Glass Industry Terms – Everything You’ve Always Wanted to Know About Glass But Were Afraid to Ask

What is frit? Frit is an industry term for the paint that is applied around the perimeter of the automotive glass parts. One of the key ingredients in frit is a glass ceramic particle that fuses to the glass surface making it a very durable and scratch resistant surface.

Why is frit (paint) on the glass? Frit serves two roles on the glass. First, it is a cosmetic feature that is used to hide interior trim and pinchweld details. Early model vehicles used wide moldings to obscure what would otherwise be exposed areas. As moldings became smaller to the point of nonexistence on several current models, the frit had a greater role in covering unfinished areas of the vehicle. Secondly, the frit inhibits UV degradation of urethane adhesives. While the frit will not completely block the UV rays from passing through the glass, it does significantly reduce UV light transmission. Most urethanes are not UV stable. If urethane is left exposed to sunlight for prolonged periods of time, it will yellow and turn chalky. Presence of the frit will extend the lifetime of the urethane adhesive system.

How many types of frit are there? There are hundreds of types of frits developed for automotive glass applications. The most common automotive glass frits we use are black, gray and white although other colors are available. Frit pastes are developed to work in combination with the processing requirements needed for a specific part. Each paste is developed for the specific furnace time and temperature parameters used to fabricate parts at a manufacturing location. It is not uncommon for a glass manufacturing facility to work with a dozen different frit pastes.

How is frit applied to the glass? Frit is applied to the glass utilizing a silk screen method. It is very similar to the method used to silk screen T-shirts. An image of the frit design is developed for the glass in the bent or curved shape. Then the image is unwrapped and flattened. A silk screen is made to allow the frit to pass through openings in the screen. The openings correspond to the final design image. The frit is a thick paste that is put onto the screen. Squeegees are used to push the frit paste through the screen openings and onto the glass. Frit is applied to the glass while it is in the flat position before it is processed through the furnace. The furnace helps to cure the frit and to fuse it to the glass surface. Every part with each different design has a unique silk screen. Silk screens are constantly being maintained throughout the life of a part. Because of the fragile nature of the screens, they will wear out and commonly need to be remade throughout the lifetime of a part in production.

What is Batch glass? Batch is a glass reference term that identifies a part of the manufacturing process. The raw components of glass are properly proportioned and mixed in batches for delivery to the furnace. Even though glass is made in a continual process that runs 24 hours a day, every day of the year, the raw materials are added as needed in batches. To state that a glass is batch glass, it implies that there is not any post manufacturing materials, i.e. a film or coating, applied to the glass. Batch glass gets all its characteristics from the raw materials that are used to make the glass. In the case of privacy or solar batch glass, the dark colorants and UV inhibitors are mixed in with the original ingredients in the batch to make the glass.

What is Float glass? Float glass refers to the glass manufacturing process. The raw components of glass are melted in a furnace between a temperature range of 240OF to 2850 F. A continual process is established as the molten glass is moved from the furnace to the tin bath where it is supported on molten tin until the glass cools from the slurry state to a temperature where the glass becomes solid. The float process was developed by Pilkington during 1950’s and is now considered the primary state of the art process for manufacturing automotive and architectural glass.

What is the tin side and what is the air side of glass? As mentioned earlier, the float glass process involves floating molten glass on.molten tin. The molten tin is smooth enough to give glass its flat surfaces. The tin and glass are like oil and water, they don’t mix. However, the side of glass that is in contact with tin during the float process does pick up a microscopic layer of tin. This is considered the tin side of float glass. The top side of glass is called the air or atmosphere side. To detect the tin side of glass, hold an UV light at an angle to the glass surface. The tin side will glow and the air side will not.

What is Soft-Ray and what is Solar-Ray’? Soft-Ray and Solar-Ray are GM Trademarks for the glass used in their vehicles. It identifies the TYPE of glass used for construction and can appear on either laminated or tempered glass. LOF uses E-Z-Eye glass for the production of Soft-Ray parts and EZKool solar control glass for Solar-Ray parts. PPG uses Solex and Solar Green respectively. Deep Tint Solar-Ray is another GM trademark that appears on dark colored solar control parts.

What is a monogram? A monogram is often referred to as the bug or trademark. Every automotive piece of glass is required by law to have an identifying mark on the glass that will be visible once that glass is in the correctly installed position in the vehicle. These marks are usually painted on the glass, but they can also be sand blasted or acid etched into the surface.

What is in a monogram? For automotive applications, there are certain governmental items that must be in the monogram including a department of transportation (DOT) number, the model (M) number and the glass type (AS-1, AS-2, AS-3 etc.) Monograms can also include information such as the brand name of the glass, the company name that made the glass, the company logo, the country of origin and a date code identifying when the glass was manufactured.

Is there anyway to determine what a part is by the monogram on the glass? Unfortunately, the majority of monograms do not have any information in it to help determine what an unmarked part is. However, we are starting to see more parts marked with the NAGS number in the Monogram. As more of this is done, it will be easier to correctly identify unknown parts.

2-What is the difference between AS-1, AS-2 and AS-3 glasses codes? For automotive applications, the three most common types of glass are AS-1, AS-2, and AS-3. All windshields must be marked with the AS-1 code which is on laminated glass having light transmission greater than 70%. All tempered glass that has light transmission above 70% is marked with an AS-2 code. All glass, laminated or tempered, that has less then 70% light transmission will have an AS-3 Code.

What is a DOT code? The DOT number identifies the glass manufacturer. The acronym DOT stands for Department of Transportation. Each glazing manufacture must apply for a DOT number in order to sell glazings for vehicles in the United States of America. Each DOT number is assigned by the government and is unique for every manufacturer. Every piece of glass that is made must contain that DOT code if it is to be sold in the automotive market.

What is an M number? The M number is a model number that is assigned by all glass manufacturing companies. Each company establishes their own M number system that is unique to that organization. The M number identifies the specific glass construction. It can identify the glass details used to manufacture a part such as glass color and thickness. One Model number might apply to 50 different part numbers. Each Model number is tested every year for compliance with the governmental regulations. Most of the time, a part number cannot be determined by the M number.

How can I determine whether the glass in a car is original or a replacement? If you don’t know the history of the car, one-way to identify a piece of glass is to check the monogram on the glass. If you, knew the manufacturer of the original glass, check the DOT (Department of Transportation) number on the glass in the car. If the DOT number doesn’t belong to the OE glass supplier, then the part was a replacement. If the number does match, then check the date code on the glass. Most manufacturers mark the monogram with a means of identifying the month and year of glass production, sometimes even the date and shift! Since each company does it differently, you’ll have to contact the appropriate manufacturer for their date code conventions, which can include combinations of letters, numbers or even dots over various letters. By comparing the date of the glass with the date of the car assembly, you can determine if they are the same vintage. If the glass date closely matches the vehicle assembly date, chances are the glass is original.

Which side of the vehicle is the right hand side? The RIGHT hand side of the vehicle is the PASSENGER’S side of the vehicle. The DRIVER’S side of the vehicle would be the LEFT-hand side. Rule of thumb, right and left sides are determined by picturing yourself sifting in the car.

When should a non-conductive adhesive be used? If the adhesive will contact the antenna or defroster lines when the part is installed, use a non-conductive adhesive. Non-conductive adhesives prevent interference with antenna systems and heated defroster systems that are contained in the glass. Many new glass parts have the antenna, defroster connections or buss bars around the edge of the glass in the same area that the adhesive is applied to install a glass part. Using a conductive adhesive will affect the performance of the electrical system. Several adhesive manufacturers offer a non-conductive product for these glass applications. Be sure to follow the manufacturers specific instructions for the adhesive system you use.

How do installation methods cause stress cracks? Installation related cracks usually result from a short cut out method, where all of the old urethane bed is not removed prior to installation. If the shape and form of the new glass is not identical to the old urethane bed, the glass could have spots of interference on the adhesive that lead to breaking. Installation related stress could also be formed by using adhesives that are too rigid and don’t offer the compression and flexibility required of the adhesive system. Usually, installation related stress cracks would develop over time after the adhesive has been allowed to fully cure.

What is tempered glass? Tempered glass is a single piece of glass that is strengthened through a rapid cooling process. This cooling process tempers the glass by blasting both the top and bottom surfaces with air. The outside surfaces of the glass cool faster than the core of the glass. This action sets up a balance of strains between the surfaces and the core which adds considerable strength to the glass. Tempered glass is difficult to break, but if broken it breaks into small granular pieces.

How are tempered parts made? Glass of the specified thickness is cut to the desired size. Any artwork or paint design is applied to the glass while it is in the flat position. This includes any heated grid lines or antenna lines required on the final part. The glass is loaded into a furnace and is heated to temperatures of 12,000 F. There are multiple processes that could be used to bend the glass as it exits the furnace including roll.

How much force is required to break a tempered backlite? While the strength of tempered glass can seem very high, it is important to recognize that the manner in which tempered glass is broken will affect the strength. Tempered glass is extremely difficult to break with dull, blunt objects. Tempered glass can have a rupture strength of up to 24,000 pounds per square inch. Recall that tempered glass is produced by rapid cooling of the outside glass surfaces which sets up a stress / strain balance.

Why do the heated grid lines on heated backlites sometimes have a redbrown color and other times have a yellow color? The color of the grid lines is predominately determined by the surface of glass that they are printed on. The lines will have a dark appearance when printed on the tin side of glass. The lines will have a brighter yellow or amber color when printed on the air side of glass. Other colors, such as white or light gray, may indicate a potential manufacturing problem with the heated grid lines such as an under fired condition or too much silver. These can result in a heated backlite that does not function correctly.

Is it a defect to see discolored spot patterns on tempered glass? No, the discolored spot patterns on a piece of glass are actually a phenomenon of the tempering process. During tempering, air is forced onto the glass through hundreds of nozzles. The spots are areas where the cool air contacts the glass. The temper spot pattern can indicate how well a piece of glass is tempered. The size and consistency of the discolored areas will vary with the exact process used, but they are present on all tempered parts. The ability to see these patterns is dependent on the angle ‘ of installation and the lighting conditions. For example, it is easier to see the patterns on a sloping piece of glass at dusk than it is to see them on a vertical piece in bright sunlight.

What is an Innershield? The innershield is a layer of plastic on the innermost piece of glass which was most commonly used on the windshield. The innershield prevented lacerations on an occupant’s head and face if they came in contact with the windshield in the event of an accident. The innershield was a popular option on deluxe vehicles about ten years ago.

How is a shadeband put into a windshield? The shadeband is pre-tinted onto the plastic that is placed between the glass plies. The plastic comes in rolls and one end of the roll has the shade color. During processing, it may be required to warp the plastic to curve the shadeband so it will match the curve of the top of, the windshield. After warping, the plastic is cut to size and it is ready to use.

What is delamination? Delamination is the separation of the glass plies and plastic layer in a laminated product such as a windshield. This is also known as an unbonded area (UBA) or an oil blow. Old autoclaving process used hot petroleum to laminate windshields and the oil could seep into the edges causing the windshield to delaminate.

What is bullet proof glass and how is it different from bullet resistant glass? Bullet proof glass is glass that will stop a bullet. Any bullet. To make a glass bullet proof, every type of bullet from every type of gun must be taken into consideration during the design of the glass. Bullet proof glass is actually a composite of glass and plastic layers laminated together to achieve a strong composite that will stop a bullet. Bullet proof glass will be three or more inches thick. Bullet resistant glass is designed for applications with a resistance to a range of specific bullet calibers. Bullet resistance glass can be obtained in a 3/4 inch thick composite of glass and plastics laminated together. On vehicle applications, the environmental end use is considered for the glass design. If a vehicle is outfitted with bullet proof or bullet resistant glazing, all the interior trim must also be reworked to accommodate the thicker glass.

What are stress cracks? Stress cracks are breaks from the edges of laminated glass, such as a windshield, that happen without an impact point or noticeable damaged area. While this phenomenon can occur with seemingly no apparent cause, there are however, two major factors that have a role in creating stress cracks. The stress crack can be caused by a manufacturing defect within the glass or it can be attributed to the installation methods.

How do glass defects cause stress cracks? Stress cracks can occur if the two plies of glass used to make the laminated part are not completely homogenous with each other. Stress cracks can be a condition of tension or compression that exist within the glass. Stress can also be caused by incomplete annealing or temperature difference between the plies. Manufacturing processes include multiple quality checkpoints for every individual part during production to identify and eliminate defective parts. Even so, it can be difficult to predict a stress crack due to manufacturing conditions.

I have often heard of a windshield surface referred to as the number 1, 2, 3 or 4 surface. What do these numbers mean? The windshield surface number refers to the glass surface of the individual glass plies in the laminated composite. A basic windshield construction is composed of two pieces of glass with a plastic layer in between. The surfaces are counted from OUTSIDE the vehicle. Therefore, surface number 1 is the outside surface of the exterior glass piece that would be exposed once installed in the vehicle. Surface number 4 is the innermost surface which would be on the interior of the vehicle once installed. Surface number 4 is the surface that is prepped with primers, cleaners and or activators required for installation. Surface # 2 and 3 are interior surfaces that are in contact with the plastic.

What is laminated glass? Laminated glass is constructed of two pieces of glass with a piece of plastic in between the glass plies. One type of plastic innerlayer used is PVB or polyvinyl butyral. Laminated glass is required to make windshields in the US.

How are windshields made? Two separate pieces of glass are cut to size. While the glass is flat it is printed with the artwork design (frit) that’s required. The glass is put through a furnace to soften the glass and fire the frit to the glass surface. Once the glass reaches the right temperature, it is molded into shape and then cooled. After shaping, the glass/ plastic/ glass sandwich is put in a clean room and then put into an autoclave. An autoclave is like a giant pressure cooker. The high pressure squeezes the glass and plastic together. The higher temperature softens the plastic, which bonds the glass and plastic layers together. Once the glass exits the autoclave, any excess plastic is trimmed and the mirror mount is applied to the glass. The glass is inspected and cleaned several times throughout the entire process to make sure it has been manufactured to the highest quality standards. After a final inspection, the finished part is now ready to ship.

What is the Breakaway Bracket? Several new GM and Ford windshields have a Breakaway Bracket. This refers To the mirror button on the windshield. This style mirror button allows the rearviewmirror to snap off when the passenger air bag is deployed. If the rear view mirror did not snap off, there is a possibility that the mirror could puncture the air bag rendering it ineffective. The accessory tool used to remove these snap off rearview mirrors is the MB-4. TIP: Put Breakaway rearview mirrors back on the glass before installing the windshield. This will prevent moving a newly installed windshield out of place with the force required to snap the mirror on the glass.

How is a windshield glass molded into shape? There are two common practices for shaping a windshield, gravity bending and press bending. Gravity bending has been used longer than press bending. For gravity bending, two pieces flat glass ride through the furnace on a mold contoured like the finished part. As the glass softens, the force of gravity pulls the glass into shape. This pair of gravity bent glass is then kept together throughout the rest of the windshield process. In a press bending operation, the single lites of glass go through a furnace on a flat surface of high temperature resistant rollers. As the glass exits the furnace it is quickly pressed into shape between a male and female mold contoured like the finished product. The glass is then cooled and moved to the next process.

How can I determine if a diversity or non-diversity antenna backlite is needed? The diversity antenna will use a combination of antennas in order to perform efficiently. Most diversity-antennas are offered with vehicle upgrade packages. A standard car model may only have the mast antenna, whereas the deluxe luxury package may incorporate a diversity antenna in the backlite with the mast antenna. How to determine the need for a diversity antenna will differ depending on the vehicle. The current Toyota Camry has extra speakers (6 total) on the vehicle that uses a diversity antenna and only 4 speakers on the vehicle that uses the non-diversity antenna.

Can an antenna or heated backlite clip be reattached to the glass if it has fallen off? Clips, or tabs, can be reattached to the glass. In order to determine if the connection is repairable, the surface of the glass must be evaluated. If there are any chunks of glass (called spalls) missing from the surface, the repair should not be made and the glass should be replaced. Spalls will weaken the glass and could eventually result in glass breakage. Next, select the adhesive to be used to reattach the clips. There are a few companies that manufacture a conductive adhesive system that can be used to reattach the tabs. The adhesive must be conductive so it will allow the electrical current pass between the lines on the glass and the vehicle. Follow the manufacture’s directions for the repair. Regular super glue adhesives will not work because they are non-conductive. HINT: Be sure to clean both the glass surface and the clip surface of old debris. Also, let the repaired part sit for the recommended cure time so the adhesive bond is fully developed.

Will a broken heated grid line on a backlite affect the operation of the antenna? Many new radio and cellular phone antenna designs are incorporated into the heated grid design in the backlite. If a heated grid line is broken it will affect the performance of the antenna. The line break will become more noticeable with the general public as diversity antennas gain popularity and reduce the need for traditional mast antennas. There are aftermarket grid line repair systems available which can restore both the heating and the antenna characteristics of the grid line.

What is a Rain Sensor windshield? Several vehicle manufacturers, including Cadillac, Mercedes Benz and BMW, are now offering Rain Sensor windshields. The rain sensor is actually a small electronic device mounted to the inside surface of the windshield. The device has a lens that will detect the presence of moisture on the outside surface of glass. When moisture is present, a signal is sent to the wiper control that automatically activates the windshield wipers. This a great safety option for those misty periods when a driver is passing trucks and road spray hits the windshield. The windshield wipers will activate without the need for the driver to remove his hands from the wheel or his eyes from the road.

Does the rain sensor module come on the replacement windshield? No. At this time, none of the rain sensor designs require the sensor to be applied by the manufacturer on the replacement windshields. The electronic sensor that is on the existing windshield in the car must be removed and re-mounted onto the replacement windshield.

How is the rain sensor attached to the replacement windshield? There are special re-attachment kits for the replacement industry, available through your local Car dealer, which can be used to re-attach the electronic rain sensor to the new windshield. The Cadillac kit consists of tape, cleaners and primers for replacing the Cadillac module. The Mercedes / BMW kit contains the tape and a new lens. Instructions for application are included in all the kits.

Is it normal for HUD display to appear faded in bright light conditions? Bright sunlight or high glare conditions can result in a dimmer display of the Head’s Up display. It is normal for a HUD to appear brighter at night in darker conditions that during the day under full sun. It is not normal for the HUD to completely disappear. If the display is fading when the car changes momentum, such as when turning a corner or accelerating, then the problem could be a system defect and it’s recommended that a dealer check out the electronics. There is nothing in the windshield to cause the display to fade or appear less intense.

What is a diversity antenna? A diversity antenna combines the reception from several individual antennas on the vehicle that makes it a very efficient antenna system. The definition of diverse means different, therefore a diversity antenna in a backlite is one that could Work with the mast (pillar) antenna mounted to the car. The two different antennas work together to achieve superior AM/FM radio reception. The 1998 Cadillac Seville has a diversity antenna system that consists of an antenna in the windshield and antenna in the backlite that work together.

What is a non-diversity antenna? A non-diversity antenna system relies on only one antenna for radio wave reception. Several examples of non-diversity antenna include 1) a mast antenna mounted to the vehicle 2) an antenna printed on the backlite or 3) a set of wires mounted into the windshield. A non-diversity antenna will not be a combination.

Can a break in a HUD (Heads-Up-Display) windshield be repaired or must it be replaced? A break in the HUD windshield can be repaired like a normal non-HUD windshield. If the repair area is in the HUD image area, a repair may interfere with the image causing a double or distorted image. Therefore, consideration is required to determine if the type and size of break is repairable without HUD interference.

Passivated glass refers to chemically coated glass. Many automotive glass parts are coated to achieve either the solar control characteristics or the privacy features. The coating can usually be detected by the reflective, mirror-like appearance. Sometimes these coatings will also have a color associated with them and can make the glass look blue, pink or amber. The solar coatings are used to filter out the sun’s ultraviolet and infrared wavelengths while the privacy coatings filter out visible light wavelengths. The wavelengths that are filtered out by coated glass, include the wavelength spectrums that CB radios, cellular phones, automated toll readers and radar detectors operate on. Therefore, the chemically coated glass can interfere with the operation of electronic devices that require a glass-mounted antenna.

What type of glass is recommended for a glass-mounted antenna? Glass that is referred to, as BATCH glass is compatible with glass mounted antennas. Solar and privacy batch glass is not coated like the passivated glass. Instead, the raw materials that give the glass its solar or privacy characteristics are added at the time the glass is made. The raw materials are melted right in with the sand and other components that glass are constructed from. Once the glass has been made, it would not need any other treatments prior to fabrication into automotive glass parts. Batch glass is uniform throughout the thickness of the glass. Coated parts are surface treated; the surface has different properties than the core of the glass.

Are there any special hints for re-attaching the rain sensor? Make sure the glass is very clean prior to attaching the sensor. The performance of the sensors depends on the optically clear grades of doublefaced tape used for reattaching the units. These tapes also need to be clean and free of bubbles when applied to the glass. Any impurities that may be present will give a false signal to the rain sensor causing it to activate unnecessarily.

What does the term “Auto-Cancel” refer to in the NAGS catalog? The Auto Cancel notation means the electrical input to the heated backlite design is automatically canceled after a specified time and/or temperature. Most heated backlites made today are for automatic cancellation systems. However, there are a few parts such as the Isuzu Trooper backlites where a different glass heated design is required for the automatic vs. the manual systems. For example, FB4815 is for an automatic cancellation heated grid system whereas FB4816 is for a manual cancellation heated grid system. 8-What is the difference between a heavy-duty heated backglass and a standard heated backglass? The heavy-duty back glass is rated for higher amperage. The Heavy-Duty (HD) designation is predominately used on foreign cars such as Honda and Toyota vehicles. Normal domestic vehicles were rated for 22 amps whereas heated backlites in Asian vehicles were generally rated for 11 amps. Amperage relates to speed of performance. The higher the amperage, the faster the backglass will heat and clear the frost from the glass. To accommodate the US market, many foreign car manufacturers developed the HD back glasses to offer compatible defrosting performance in the US. The heavy-duty backglass are an upgrade, but it does not interchange with the standard design.