Note 10 Plus Back Glass Scratching Easy

Why your brand-new smartphone will scratch just as easily as your old one

For years, Gorilla Glass' scratch resistance on smartphones has plateaued

By Oct 19, 2018, 11:21am EDT

Photo by Amelia Holowaty Krales / The Verge

Every year, your favorite smartphone gets better specs that boost its processing speed, data security, and picture quality. But one remaining constant is scratch resistance, which does not seem to have improved year over year.

Most smartphones are covered with Gorilla Glass, a glass made by Corning that's been specifically engineered to protect against drops and other damage. But devices with that glass are still prone to scratches if you place them in the same pocket as your keys and coins. Even if you don't, it doesn't take long for a phone to collect all kinds of scratches just from daily use. And if complaints about the iPhone X, Pixel 2, and other flagships from the last year are any sign, the situation has been getting worse, with modern phones scratching from the slightest mishandling.

So are we imagining it, or are newer versions of Gorilla Glass less scratch-proof than ever? While it's hard to say definitively whether they're getting worse, even Corning's own numbers show they aren't getting any better.

The reason why has to do with both market demand and glass' natural qualities. Since glass can't truly be both extremely drop resistant and scratch resistant, Corning and other glass makers are forced to choose which of those two qualities to prioritize. For Corning, drop resistance takes precedence.

Corning's decision to focus on harder, crack-resistant glass dates back the story of Gorilla Glass' origin. Steve Jobs asked Corning's CEO to make a glass cover that would protect the iPhone from scratches and cracks. Prior to the iPhone, touchscreen smartphones used soft plastic on top of their displays, which was suitable for a stylus, but terrible for finger touch interactions. Corning only had a six-month window to deliver the goods, and that's how the first Gorilla Glass was born.

Like the initial request to create Gorilla Glass, Corning's objectives today have been shaped by the demands of smartphone makers. As the Samsungs, Apples, Huaweis, and Googles of the world ask for thinner and lighter glass, Corning in turn has to make that thin glass stronger to keep up its drop resistance. Corning's VP of Gorilla Glass, John Bayne, made note of the conflict to Digital Trends last December, "The number one pain point for consumers is still broken devices, so we have prioritized drop with recent generations of Gorilla Glass."

Smartphones that use Gorilla Glass 5 — the generation of glass introduced in 2016 and found on Samsung's Galaxy devices, the LG G7 ThinQ, and the OnePlus 6, to name a few — have benefited from the glass's greater resistance to taking damage from falls, as compared to its predecessors. And Corning claims the latest and greatest Gorilla Glass 6, which should start showing up on phones this fall, can survive 15 drops from a one meter height.

To achieve this strength, Corning has had to transform glass, which is naturally fragile. By soaking glass in a chemical salt bath, the company also introduces compressive stress into the inside of the glass. That internal stress helps counteract any drops and falls the glass might face in the future once incorporated inside a smartphone. Over the years, as smartphone makers demand thinner glass to incorporate into sleeker phone designs, Corning has had to introduce more and more internal stress to keep up the resilience. It works well in theory and has produced plenty of more drop-resistant generations, but in exchange, the internal stress makes the glass easier to scratch.

The main way that glass makers strengthen glass is through tempering, which can either be an intense heating process or a chemical treatment, like the aforementioned salt bath. As Caltech professor of materials science William L. Johnson explains, the internal stress causes the glass to yield more easily to any introduced stress on its surface. In simple terms, that means when the glass is more tempered, it often scratches more easily. (Corning contends that tempering improves both drop and scratch resistance.)

Johnson says that, ultimately, it all comes down to how hard the surface of the glass is. Tempering gives up added hardness in favor of flexibility. More tempering "makes the whole screen more tolerant to overall bending, as in dropping the phone," he says. "But it does not necessarily improve the hardness of the glass [and] might actually make it slightly worse. It's the hardness that enables scratch resistance."

According to Corning's own tests, Gorilla Glass' scratch resistance hasn't improved since 2014. While Corning says the glass got more scratch resistant during early generations before plateauing in recent ones, it switched up the tests used on its product information sheet, making it hard to compare metrics between Gorilla Glass 3, 4, 5, and 6.

In 2013, Corning used a "Knoop Visual Scratch Test," but the next year, it made no mention of scratch resistance at all, so we're unable to draw a line through the earlier glass generations. "We've changed our test methods over time, with slight variations on each test," Corning's VP of Gorilla Glass Scott Forester tells The Verge. "Scratch is a very complex space. You're not seeing a huge degradation in scratch, but you're seeing a huge improvement in drop."

If we were to go by the results of the Taber Test, we can say that the older Gorilla Glass 3 is more scratch resistant than 4

Image: Corning

Gorilla Glass 5's product information sheet from 2016, however, is telling. It presents three tests — the Taber Test, the Garnet Test, and the Tumble Test — and their results. In the Taber Test, which measures wear from prolonged abrasion, Gorilla Glass 3 appears visibly less scratched than Gorilla Glass 4, and Gorilla Glass 5 looks to be somewhere in between the two. The Garnet Test, which puts the glass up against sandpaper, presents more visible scratches in some areas and more faded scratches in others for Gorilla Glass 5, making it hard to draw a definite conclusion. Gorilla Glass 3 and 4 look more consistently scratched throughout.

If we were to go by the results of the Taber Test, we can say that the older Gorilla Glass 3 is more scratch resistant than 4. But once we take other contradicting results into consideration, it's harder to draw a conclusion.

Gorilla Glass 6 comes across more scratched up than 5 on the Tumble test.

Image: Corning

By focusing on photos on the product sheet, without including measured results that can be objectively interpreted, Corning avoids giving concrete answers on its product's scratch resistance.

However, the company has stated hard statistics in the past: according to the Tumble test from a few years ago, which tests the glass after a "random purse tumble" for 15 minutes, the surface area of Gorilla Glass 3 came away 0.52 percent damaged while the surface areas of Gorilla Glass 4 and 5 were both 0.39 percent damaged, indicating an improvement. Corning also confirmed to The Verge that the number remains the same for Gorilla Glass 6, meaning the last two generations have made zero improvements in this department.

In certain tests by Corning, the newest generation of Gorilla Glass even looks more scratched up than an older one. In particular, Gorilla Glass 6 looks worse than 5 when looking at this year's product sheet for a test that simulates having coins next to the screen.

Forester, the Gorilla Glass VP, said that one test alone can't quantify scratch resistance performance. "For scratch, there are so many ways to test it … and different tests create different levels of damage," he said. When asked why Corning stopped sharing hard numbers after Gorilla Glass 5, Forester said the company chose not to because it made the product sheet look cleaner.

Forester denies that the company has lost scratch resistance over the years, claiming that you can't see a difference when looking at smartphones "on the macro level," or from a distance. He also points to the trade-off between thinness of glass and its durability and strength; Forester claims that when Corning presents major OEMs with more durable glass, the feedback is always that the glass should be thinner.

New Gorilla Glass generations may be thinner, but if they remain prone to scratches, users are likely to buy screen protectors that add that thickness back in anyway. And while screen protectors aren't expensive, it can be annoying for those already forking increasingly sky high prices for a brand-new flagship. A scratched up screen also significantly decreases the value of a phone when you're trying to resell it.

Meanwhile, Corning does have a solution within its own portfolio, but the company says it won't be ready for sometime. Gorilla Glass SR+ and DX+, found in the new Samsung Galaxy Watch, are new variations of glass made for smartwatches and other wearables with a focus on scratch resistance. However, Forester says these two glasses face a scaling issue and that Corning can only use them for wearables at this time.

"We initially created SR+ to go after the scratch resistance of sapphire. It's a unique glass composite. We started out in the wearable space because it seemed like the most applicable use case." If SR+ and DX+, or perhaps a future iteration of a different name, can arrive on smartphones, that could finally give us the scratch-resistant phones we're looking for.

For now, when we get a new phone, we'll have to keep shelling out for a case to protect its sleek all-glass body and stick on a screen protector to prevent scratches. As YouTuber JerryRigEverything, famous for his destructive phone tests, puts it to The Verge: "Glass is glass, no matter what 'variation' it is. One variation might be slightly better than another, but it's all still within the same realm of glass."

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Source: https://www.theverge.com/circuitbreaker/2018/10/19/17514174/gorilla-glass-scratch-resistance-google-pixel-3-samsung-galaxy-s9-note

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