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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

 

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