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. GlassPaint H2O
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.