No, aluminum will not scratch glass.
This is due to the hardness of each material when comparing measurements on the Mohs hardness scale.
Can Aluminum Scratch Glass? (EXPLAINED)
Background on Glass
The first glass ever made was composed of sand quartz and used by ancient civilizations such as the Egyptians and Phoenicians in the form of beads and other simple objects.
However, despite the simplicity of early glass materials, sand quartz registers as a 7 on the Mohs hardness scale, meaning that if aluminum were in use thousands of years ago, it still couldn’t scratch glass.
Modern day glass, however, typically has a much more complex chemistry in contrast to its earlier predecessors.
Typical commercial glass rates at 5.5 to 7, while aluminum only registers at 2.75.
The sand, or silicone dioxide (SiO2), is mixed with other materials such as soda ash (sodium carbonate or Na2CO3), and limestone (calcium carbonate or CaCo3).
Adding these extra ingredients makes modern glass easier to manufacture and more durable.
The soda ash helps lower the melting point of silicone dioxide from 2000 degrees Celsius down to 1000, making it easier to shape into whatever form the maker chooses.
However, the soda ash also softens the mixture, so limestone is added to increase the hardness and overall chemical durability of the finished glass product.
Glass as we know it today is transparent to visible light, an inert and biological inactive material, and solid.
With its ability to repel corrosion, deterioration, fading, even staining, glass is known as one of the best materials for packaging.
It is used in multiple applications, such as electrical transmission, textiles, windows and other structures on buildings, optical tools, and instruments intended for detailed scientific research, just to name a few.
Background on Aluminum
The first pure aluminum crystal was extracted in 1825 from ore by Hans-Christian, a Danish chemist.
The material, however, didn’t reach commercial potential till around 1889, as at the time of its discovery, aluminum was considered more precious than gold or silver!
Considering how expensive it was to produce pure aluminum metal at the time, aluminum bars were displayed alongside the French crown jewels at the Exposition Universelle of 1855, and the material was also made into dinner ware for Emperor Napoleon III’s “honored guests”.
Once cheap and commercially viable methods were put in place, the metal moved on to be used for electrical wiring and even engine parts on the Wright brothers’ first biplane in 1903.
Today, aluminum is known to be the most abundant metal on Earth, and is used in a lot of things such as foil and airplanes.
Due to its strength, light weight, and non-corrosive properties, this material is among the most used metals on Earth.
It’s commonly extracted from what’s known as Bauxite ore, a mineral composed of aluminum oxide, silica, and iron dioxide.
Such ore is extracted from top soil using environmentally friendly strip-mining operations in countries such as Australia, India, China, and even Jamaica.
Pure aluminum is extracted using the Bayer process, a method using high heat and pressure to produce aluminum precipitate.
The product then undergoes the Hall-Heroult process, an industrial method that smelts aluminum into the material we know today.
Even though this process is known to be very energy intensive, 95%-98% of all aluminum today can be recycled, meaning a majority of the material does not have to be extracted using robust industrial methods.
Glass vs Aluminum
Aside from the typical windows and smartphone screens we see on a daily basis, there are several forms of glass used for several different purposes.
The hardness of each type varies on the materials that are infused into them.
One such example is lead glass. Industries that use this type include nuclear, medical, and space technologies due to lead being able to absorb gamma radiation.
Adding a certain mixture of lead oxide (PbO) to glass, around 13-15%, can increase durability and bring its Mohs hardness up to 6.
As we have compared before, with aluminum measuring 2.75, lead glass cannot be scratched by the metal.
Another is borosilicate glass.
Aside from 70-80% sand content, this material also contains 7-13% boron trioxide, 4-8% potassium and sodium oxide, and 2-7% aluminum oxide.
This unique composition brings its Mohs hardness up to 7.5, slightly harder than most commercial glass used today.
This material is used for containing pharmaceuticals such as injectables, lamp covers, and other applications that require chemical containment or high temperature fluctuations.
Considering its hardness factor, it will not be scratched by aluminum metal.
However, many aluminum products today do not use the pure metal by itself.
There are several aluminum alloys out there that contain a variety of metals, such as 7068 aluminum alloy, one of the strongest that is commercially available.
Whereas aluminum on its own can be quite fragile, adding other metals such as iron and titanium gives it an increased hardness.
As Titanium on its own has a Mohs hardness of 6, it’s possible that 7068 aluminum alloy could scratch glass.
As for the actual Mohs hardness of the material, it’s difficult to say, as any information on that specific aspect is not readily available.
For those who cook with aluminum cookware on glass stoves, you might have noticed unsightly marks on the glass from general wear and tear.
Aluminum alloys such as 1100 aluminum or 3004 aluminum are commonly used for pots and pans, so can those scratch glass?
Not necessarily, the resulting marks can be from the metal rubbing off on the glass itself, giving your stove the appearance of scratch marks.
Applying some bleach to the marks can help get rid of them.
Whereas the possibility of aluminum alloys scratching glass exists, the fact of the matter is that aluminum by itself is not hard enough to scratch glass.
You might also like: