A RETROSPECTIVE GUIDE TO AUTOMOTIVE GLASS
One of the most time-consuming and temperamental processes for a detailing technician is that of restoring automotive glass. Of course, before one gets their hands dirty, this category necessitates a closer look into how automotive glass has evolved throughout the last 100 years.
Believe it or not, it wasn't until 1904 that the first windshield was manufactured, but its only purpose was to shield the driver from unwanted debris. Despite its minimalistic design consisting of only two horizontal panes of thin, single-pane glass, it was practical in every way yet left much to be desired in the way of safety. Once the top pane had been clouded with excessive debris, the driver could simply fold the top half down exposing the second pane.
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ILLUSTRATION OF THE FIRST-MANUFACTURED WINDSCREEN DESIGN
The major flaw in this technology was that even though it would shield the driver from any oncoming projectile, the sheet of glass was absurdly thin, resulting in serious injuries and random shards of glass shattering into oblivion. Over the next 30 years, vehicle production increased which naturally led to more and more injuries. In response to this epidemic, a French chemist by the name of Edouard Benedictus had serendipitously found his way into the automotive arena while experimenting with glass of different varieties.
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PHOTOGRAPH OF EDOUARD BENEDICTUS
Among his many different exploits, glass was one that he had always grown fond of. Thankfully after 15-20 years of trial and error, he had ushered-in the first modernization of what we know today as the shatterproof windscreen. Interestingly enough, Benedictus was preoccupied with another project and while working in his home, a glass flask had fallen onto the ground breaking into many pieces. However, rather than the flask shattering, he noticed that the glass had stayed intact because of one component that had bonded it all together, and this piece was known as cellulose nitrate.
In the same fashion, windows and surrounding glass had undergone the same transformation with traditional panes shifting into safety glass (laminated glass), which then finally evolved into tempered glass. While safety glass was a dramatic improvement from basic sheets of thin glass, the susceptibility of one injuring themselves in a collision was still higher than that of tempered glass. From its breaking point, safety glass will crack into larger pieces while tempered glass will shield the driver by breaking into many smaller pieces, thereby greatly reducing the risk of injury to the driver and any passenger.
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ILLUSTRATION AND CROSS-SECTION OF A PIECE OF SAFETY GLASS (LAMINATED GLASS)
From a manufacturing standpoint, safety glass is comprised of piecing together two sheets of glass, with a formulation containing elements such as silica fine sand, soda ash, dolomite, cullet, and a mixture of others. An integration of polyvinyl butyral is then thrown in-between, which then fulfills its safety component. Conversely, the process of creating tempered glass involves laminating multiple sheets of glass through a very slow manufacturing process known as "annealing". When annealing is executed, multiple layers of glass are heated to its maximum temperature threshold, and are then subsequently cooled at its slowest rate to ensure recrystallization of the atoms in each layer for optimal density and hardness. To date, at least for an overwhelming majority of mass-produced manufacturers, either tempered or laminated glass are used. Additionally, it should be known that modern automotive glass (tempered and laminated) contain minimal hydrophobic properties. Although glass alone is porous, the formulation in vehicles contain membranes that will resist adverse weather conditions as mandated by the NHTSA and other government-regulated organizations.
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ILLUSTRATION OF THE ANNEALING PROCESS WITH RELATION TO TEMPERED GLASS AND ITS PRIMITIVE COUNTERPARTS
It wasn't until 1937 that safety glass was mandated in all vehicles, and was therefore the leading form of glass installed in most vehicles. Of course, a lot has changed since 1937 and as we inch ever closer to 2022, specialty shops and restoration operations of many different descriptions try to replicate the specs of various models, especially classic cars. However, it should be known that for any street-legal vehicle, the minimum requirement is to install safety glass for obvious reasons.
The video below demonstrates the difference in tension displaced on a single sheet of glass between a lesser form of glass and tempered. As you can see, great measures have been taken to ensure the greatest level of safety to both the driver and passenger.
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VIDEO SHOWCASING HOW SAFETY GLASS WORKS IN MODERN AUTOMOBILES
Not unlike your paintwork, your automotive glass can fall victim to an onslaught of hazards including micro-marring, water-spotting, off-gassing film from VOC's (volatile organic compounds), semi-permanent iron and mineral deposits left from unfiltered water. and smoker's film.
While one remedy begets another, sometimes it can be overwhelming to determine what process is right for your particular set of circumstances. The three criteria that one should fulfill to ensuring a streak-free finish include working clean, working methodically, and being patient. As a prerequisite to executing any of the methods listed below, ensure that the surface you're working on is completely free of any contamination. Therefore, it's vital to perform a thorough wash and clay bar process prior to moving any further.
METHOD 1: REGULAR MAINTENANCE
If you should be one of the lucky ones who doesn't possess any of the hazards listed above, a set of two glass-specific towels and a trusted diluted glass cleaner (ammonia-free) is all that you'll need. Rather than spraying your solution directly onto the glass, saturate one of your towels with enough solution so that it's wet but not to the degree of being damp.
Next, take your saturated towel and move from left to right ensuring complete coverage. With your second dry, glass-specific towel on deck, wipe any excess in the same motion (assuming you're beginning with the exterior of your glass). Look closely to see if any remaining streaks are left, because you'll most likely miss one or two areas that have yet to be perfected (corners and deep crevices that rest around the edges).
In a similar fashion, take another set of two towels and repeat the same process to the interior of the window. However, this time around, be sure to wipe with an up and down motion so you can identify which areas of the window hadn't been addressed on the outside. By using the left to right and up to down process, you'll be able to eliminate the risk of "chasing your tail" so you can expedite the window cleaning process.
If your vehicle should have aftermarket tint, be sure to use the least-invasive method by applying the least amount of pressure to the glass. By doing so, the risk of lifting any corners of film will be greatly reduced.
METHOD 2: OFF-GASSING & VOC'S
Congratulations on taking delivery of your new vehicle. No, we're not talking about a slightly used vehicle but rather a vehicle that had been produced within the first year of being assembled from the factory. It should be known that chemical compounds that reside within the membrane of various plastics will go through a process known as "off-gassing". When this happens, these invisible compounds have nowhere else to escape other than sticking to the inner membrane of your automotive glass. In some cases, you may be able to get by with using the aforementioned process listed above, but if you should find yourself in a sticky situation and multiple streaks should arise, it's time to reach for something stronger.
Using melamine foam pads (magic erasers) will grip and pull off any remaining debris. Simply submerge your pad into lukewarm water, and squeeze any excess leaving the pad saturated but not dripping wet. In some cases, particularly windscreens and back windows, you may need to apply additional pressure to ensure that everything is removed. From there, this will allow you to use the conventional two-towel method listed in the first method.
METHOD 3: IRON & MINERAL DEPOSITS
Trust me, it happens to all of us at some point during vehicle ownership. You're driving in a residential area during the peak of spring or summer, and a stream of water comes jutting out and inexplicably lands on your glass. If not addressed with a sense of immediacy, the impurities within the water that landed on your glass will sit for an extended period of time and etch their way into the top layer of glass leaving behind iron and mineral deposits. What's worse, the sun will act as a catalyst causing them to bake even further into the outer membrane. Unfortunately, this level of damage stretches beyond that of a simple towel and cleaner.
Depending on the severity of the deposit, you'll most likely have to reach for a polisher and either a light to medium polish to get the job done. Much like that of paintwork, work the affected area in a crosshatch pattern at a low to medium speed coupled with light to medium pressure. If you find that a light polish won't rectify the issue, then advance to a medium-cut polish along with the same trusted polishing pad.
If the circumstances are dire, a traditional polisher (DA, direct-drive, or rotary) may not be aggressive enough. If this is the case, then it's time to employ the use of specialty solutions that cut into the membrane even further. Although challenging, it's imperative that you use the right tools for the right job, which is why I strongly endorse the Diamondite Glass Polishing System. With a higher percentage of cerium oxide integrated within the formula, this kit works its magic against not only iron and mineral deposits, but works extremely well against smaller scratches and other similar forms of defects.
If you're looking for a cost-effective solution, reach for a can of Bar Keepers Friend. This light abrasive contains trace amounts of oxalic acid. Of course, when handling anything with acid, it should be used sparingly. With either a microfiber towel or microfiber applicator pad, pour a dime-sized amount of Bar Keepers Friend into your media and mix with a small amount of lukewarm water. Work with medium pressure onto the affected area in straight lines (up and down, and left to right). After 5 passes (1 pass equates to a cycle of moving from up and down and left to right) rinse and dry. Repeat this process until you achieve a desired result.
While this blog may not cover the farthest expanses of automotive glass, it should still arm you with a little knowledge and insight as to how these temperamental pieces work and the purpose it serves to anyone behind the wheel. Below you'll also find a link to products that should help you restore clarity to your automotive glass, including anything that might resemble glass inside your cabin. Other dedicated blogs will follow reviewing protective coatings related to automotive glass, so stay tuned.
Window Cleaner & Glass-Specific Towels
Meguiar's Glass Cleaner Concentrate
Stoner Invisible Glass
Stoner Glass Hard-To-Reach Cleaning Mop
Dry Me A River Glass Cleaning Towels
Iron & Mineral Deposit Remover
Diamondite Glass Polish
Polishing Pads
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