Japanese researchers have found a way to make stiffer and harder glass. However, reports that it could mean phone screens stronger than steel are misleading at best, partly because of confusion over what has been measured.

The work by the University of Tokyo and the Synchotron Radiation Research Institute, doesn’t involve any new materials, but rather a more effective production method.

Most toughened glass is based around silicon dioxide, but with the addition of alumina (aka aluminium oxide, pictured) to boost strength. To date the problem with that technique is that it’s difficult to increase the alumina content without the mixture touching the edge of its container and crystallizing.

The researchers tried a different approach, dropping the silicon dioxide altogether. Instead they used high pressure to crush together oxide powders of alumina and tantalum (an element commonly used in capacitors.) Rather than put the resulting substance in a container, they levitated it with oxygen gas and melted it with lasers, creating (extremely small) spheres of glass.

As well as meeting the basic requirements for glass (being colourless and transparent), the spheres performed well on several tests of resilience, but that doesn’t make it harder than/stronger than/stiffer than steel.

To be specific, the glass scored well for Young’s modulus, a measure of stiffness or rigidity. In simple terms, that means it takes a lot of force to deform it by changing its shape. While the rating was above that of some metals, it was still less than that of steel.

The glass also scored well on the Vickers test, which measures hardness. That’s effectively how much resistance the material puts up against something that is trying to penetrate it.

The testing didn’t specifically cover strength or toughness. The former is how much force a substance can withstand and still be able to recover its original shape. The latter, which is particularly relevant to phone screens, is how much force it can withstand (specifically how much energy it can absorb) before it fractures.

Potentially misleading marketing aside, it’s certainly the case that a screen made from this glass would be more resilient to some sources of damage than existing phone screens. However, it would not be unbreakable, and in any case there’s still a long way to go from creating tiny spheres to using the same technique to create an entire sheet of glass for a screen.