You’ve likely seen the video: Zack from JerryRigEverything performing his now-familiar durability test on the Samsung Galaxy Note 7. Surprisingly, he appears to leave visible scratches on the device’s Gorilla Glass 5 with a metal pick that rates a 3 on Mohs scale of hardness – “only one step above plastic,” as Zack notes in the video. A new glass from Corning that appears to scratch much more easily than its predecessor is admittedly hot news, but as is often the case, the “scandal” may have gotten blown a little out of proportion.

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For some context, in Zack’s previous videos on devices typically using Gorilla Glass 4, it usually takes a 5 or 6 hardness pick before scratches occur. But in the Note 7 video, non-removable marks are visible on the screen from a pick as low as 3. Based on the video evidence, many have jumped to the conclusion that increasing Gorilla Glass 5’s shatter-resistance has come at the cost of weakening its scratch resistance. Not being a materials scientist myself, I reached out to Corning for their take on what the video seems to show.


I spoke with two of Corning’s senior spokespeople, Jaymin Amin, Corning’s vp of technology, and Jon Pasansky, Corning’s business technical director for Gorilla Glass. For starters, and as you may have already guessed, concerns were raised about the reliability of the test itself.

The test that was conducted in the video is not a bonafide industry test. It's using Mohs hardness picks but it's in an uncontrolled manner.
Amin noted, “the test that was conducted in the video is obviously not a bonafide industry test. It’s using Mohs hardness picks but it’s in an uncontrolled manner. We also don’t know a whole lot about what loads the person has used. Whether those loads are changing as he goes through the testing.”

I argued that Zack has performed this test over 30 times and that even outside a laboratory setting, there must be at least some degree of consistency in his approach and execution. The idea was shut down immediately, with the (apparently obvious) fact that all glass falls between a Mohs hardness of 5-6, something which Pasansky told me “has been validated several times during the development process here at Corning.” So a Mohs pick of 3 cannot scratch glass with a hardness of 5 or 6. So far so busted.

A Mohs pick of 3 cannot scratch glass with a hardness of 5 or 6.
Galaxy Note 7 - Gorilla Glass 5 Scratch Test 3
So if the Gorilla Glass 5 in the video is indeed a 5 or a 6 on Mohs scale of hardness, what gives? The answer is actually quite simple, and one that probably should have been self-evident. As Amin explained:

The hardness pick that was used in the video was a 3, that’s considerably softer than the glass material. Oftentimes when you have a softer material like that, and depending on what kind of loads you have used, you tend to see material transfer on the test substrate.

Material transfer on the test substrate is not necessarily a scratch but it can appear to the untrained eye as a pretty visible scratch. We don’t know whether or not that is what is being seen in the video. Certainly in the testing we’ve done internally, we don’t see that issue at all with similar picks on the Mohs hardness scale.

Galaxy Note 7 - Gorilla Glass 5 Scratch Test 1
Pasansky expanded by saying, “We have conducted controlled pick hardness tests on GG5 and we have demonstrated that this material transfer phenomena can occur. It is characteristic of the lower pick hardnesses during the tests.” So, if Corning’s theory is accurate, what we’re likely seeing in the video is actually the metal pick “rubbing off” on the glass material, not the pick scratching the glass.

What we're likely seeing in the video is actually the metal pick “rubbing off” on the glass material, not the pick scratching the glass.
But the video certainly seems to show progressively worse scratches as the pick hardness increases – which would be logical if indeed the pick is scratching the glass. So if what we’re seeing is a soft material being transferred onto the glass, shouldn’t the effect become less noticeable as the picks become harder? Pasansky explained:

“It’s a function of the difference in the hardness of the materials, but in particular the load is very important. So you could have a lower hardness pick with a much higher load and still achieve a condition that would look like a slightly higher hardness pick with a lighter load. It’s a combination of pressure and material hardness differences that exist between the pick and the material that’s being contacted.”

Corning clearly doesn’t want to accuse Zack of rigging the results, but something still didn’t seem quite right to me. Inverting the hardness and load for a pretty banal scandal seemed all too Machiavellian for a YouTuber. To get everything out in the open, I asked if Gorilla Glass 5 was at least as scratch resistant as Gorilla Glass 4. The response felt a little like it dodged the question.

“The glass is designed to improve the drop performance and not necessarily designed to improve the scratch performance,” Amin told me. He went on to say, “When we consider all hardness tests, GG5 is actually harder than GG4. Based on our testing, for scratch performance as well as the hardness testing we do that’s widely used in the industry, we believe that GG5 should be performing similarly to GG4.”

The use of the word “similarly” struck me. The same word appears on the product information sheet for Gorilla Glass 5. The kind of promotional material that is typically overflowing with percentage increases and quantifiable numbers. Saying “similar” sounded like Gorilla Glass 5 might not be as scratch resistant as its predecessor, so I asked again: is Gorilla Glass 5 at least as scratch resistant as Gorilla Glass 4? The answer: “Yes, that is correct.”