Wikipedia:Reference desk/Archives/Science/2020 November 20

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November 20

perfect glass

An image is worth a hundred words: the regularity of the arrangement of atoms determines whether a solid is "crystalline", "polycristalline" or "amorphous".

I've read that theoretically, if we made a glass which its crystal was perfect we get a much harder material. My question: it will be breakable ( by domestic usage, such as falling glass?). What other properties will be different from regular glass?--Exx8 (talk) 14:51, 20 November 2020 (UTC)

It is unclear what you mean by "perfect crystal" of glass. Glass is amorphous (non-crystalline) by nature. So anyone who is saying "perfect crystal of glass" is basically speaking bullshit and doesn't know what they are saying. There are crystalline forms of silicon dioxide (the chemical compound that makes up glass); this is called Quartz, and is fairly hard (7 on the Mohs scale) on its own. It's also fantastically common, one of the most common minerals on earth. It's not particularly rare or magical or hard to obtain. If you've been to a beach, most of the sand you are walking on is quartz. --Jayron32 14:57, 20 November 2020 (UTC)

Common glass is 70-74% quartz soda-lime glass though, soda to make the quartz melt at glassblowing temperatures instead of much higher, the third compound to keep glass from dissolving when it touches water or saliva. And soda-lime glass says there's also aluminum and magnesium oxides and other additives in the mix. Common glass Mohs number (scratchability only, diamonds have been broken by hammers that can't even scratch glass) is quartzy so maybe the monocrystalline version of common glass is as mundane as quartz crystal in fragility but that's not guaranteed without unmelting some glass slowly enough to make crystals the size of common glass objects and grinding or cutting the crystal into a window or cup say and comparing fragilities. Has this been modelled by computer? Sagittarian Milky Way (talk) 18:06, 20 November 2020 (UTC)

I added a good image to explain the scientific jargon at hand here, which the OP probably ignores.

The question might also come from a confusion with "crystal glass", a misleading common term for (non-crystalline!) lead glass (or similar modern, non-leaded products imitating its properties). Tigraan^{Click here to contact me}

I refer to the state described here with the enormous tensile strength:

https://en.wikipedia.org/wiki/Strength_of_glass--Exx8 (talk) 15:29, 20 November 2020 (UTC)

There's nothing there. I assume you're referring to Strength of glass. It's proper URL would be https://en.wikipedia.org/wiki/Strength_of_glass Your -- thingie ran into the URL. ←Baseball Bugs ^{What's up, Doc?} carrots→ 15:54, 20 November 2020 (UTC)

yes--Exx8 (talk) 16:23, 20 November 2020 (UTC)

The imperfections that so drastically reduce the tensile strength are not imperfections in a (non-existent) crystal lattice, but mainly minute cracks, typically on the surface, that may be invisible to the eye. When a layer of glass bends under a force, these cracks quickly grow deeper and longer on the side of the surface that is stretched by the bending. (But what is this thing of a glass fibre being strong due to having "have less surface area than regular glass"? What does that mean? For a cylindrical fibre of radius r, the surface-to-volume ratio is 2/r. For a flat sheet of glass whose thickness equals d, that ratio is 2/d. Typically, d >> r, the former being measured in millmetres and the second in microns, so regular glass has a much lower surface-to-volume ratio.)  --Lambiam 17:05, 20 November 2020 (UTC)

so will a perfect glass be unbreakable?--Exx8 (talk) 17:08, 20 November 2020 (UTC)

No, nothing is unbreakable. Even without any of the above-mentioned surface imperfections, glass is still fairly brittle, meaning with sufficient force of any kind, it will still break. There are ways to make glass more or less strong, so there is an optimum production technique to make it as strong as it could be, but "unbreakable" is not a thing. --Jayron32 17:50, 20 November 2020 (UTC)

A science teacher told me that about anything would be much harder to break with your hands or Superman's hands if you had to break every chemical bond without help from imperfections down to the size of atoms or molecules. If by perfect one means every atom perfect then nothing is perfect and singling out just glass for this magical property would be misleading. Sagittarian Milky Way (talk) 18:38, 20 November 2020 (UTC)

Your science teacher seems to have been unaware of the full range of Superman's powers and abilities. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:03, 21 November 2020 (UTC)

I'm sure Supes could tell the atomically flawless copy is harder to break than the real one even though for him is like toothpick. He can use elevator buttons and poke jail bars like wet noodle with the same finger right, good muscle memory range is a required secondary superpower. Sagittarian Milky Way (talk) 23:49, 21 November 2020 (UTC)

Quartz glass, btw, is an actual thing that we make for various uses. For example, a quartz cuvette is necessary for many forms of UV/Vis absorption spectroscopy. Traditional, amorphous glass blocks the passage of UV light, so if you are interested in measuring UV absorption of a sample (for example, if you are examining a protein containing sample where the aromatic amino acid residues absorb in the UV), then you can't use a plastic or a traditional glass cuvette. You need a cuvette made out of quartz. These are expensive, but not rare. For circular dichroism measurement (usually used on proteins), quartz cuvettes are near ubiquitous. Quartz cuvettes and microscope slides are also better to use when performing Raman spectroscopy. You do feel way worse if you break one, though, than if you break a glass cuvette. Each quartz cuvette can run you over $100, while a glass cuvette is probably a few cents. --OuroborosCobra (talk) 20:34, 20 November 2020 (UTC)

I'm talking about unbreakable for domestic usage. Like throwing a glass onto the wall or the floor...--Exx8 (talk) 20:48, 20 November 2020 (UTC)

The article Tempered glass explains how glass is strengthened. A tradeoff is that tempered glass cannot be drilled or ground because it will shatter into chunks however this is safer that the jagged shards of ordinary broken glass. PYREX is the brand name of a glass formulation that has low thermal expansion, suitable for cookware. 84.209.119.241 (talk) 00:22, 21 November 2020 (UTC)