# Is transparent aluminum even remotely possible? **URL:** \ **Category:** Factual Questions\ **Created:** [October 26, 2014, 6:11pm UTC](https://boards.straightdope.com/t/is-transparent-aluminum-even-remotely-possible/702586 "2014-10-26T18:11:42Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Ficer67](https://avatars.discourse-cdn.com/v4/letter/f/c57346/32.png) [@Ficer67](https://boards.straightdope.com/u/Ficer67)\ **Post date:** [October 26, 2014, 6:11pm UTC](https://boards.straightdope.com/t/is-transparent-aluminum-even-remotely-possible/702586/1 "2014-10-26T18:11:42Z")
In the movie, Star Trek IV - The Voyage Home, Mr. Scott trades the formula for transparent aluminum for a quantity of plastic. That’s great for the movie. But is transparent aluminum even remotely possible? Thanks Ficer67 ---
**Author:** ![running\_coach](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/running_coach/32/15836_2.png) [@running\_coach](https://boards.straightdope.com/u/running_coach)\ **Post date:** [October 26, 2014, 6:14pm UTC](https://boards.straightdope.com/t/is-transparent-aluminum-even-remotely-possible/702586/2 "2014-10-26T18:14:44Z")
[Kinda.](http://en.wikipedia.org/wiki/Aluminium_oxynitride) ---
**Author:** ![Ficer67](https://avatars.discourse-cdn.com/v4/letter/f/c57346/32.png) [@Ficer67](https://boards.straightdope.com/u/Ficer67)\ **Post date:** [October 26, 2014, 6:22pm UTC](https://boards.straightdope.com/t/is-transparent-aluminum-even-remotely-possible/702586/3 "2014-10-26T18:22:27Z")
I guess that answers my question. I don’t know why I did not find that in Wikipedia… Thanks Running Coach ---
**Author:** ![Captain\_Amazing](https://avatars.discourse-cdn.com/v4/letter/c/6de8d8/32.png) [@Captain\_Amazing](https://boards.straightdope.com/u/Captain_Amazing)\ **Post date:** [October 26, 2014, 6:22pm UTC](https://boards.straightdope.com/t/is-transparent-aluminum-even-remotely-possible/702586/4 "2014-10-26T18:22:43Z")
There are transparent aluminum compounds, like Aluminium oxynitride, marketed as ALON, which is a ceramic that’s being considered as armor, because it’s bullet resistant and lighter than bullet resistant glass. It’s also more expensive to make though, which is why it’s not yet in common use. Still, if you want to see a piece get shot, and how it compares to traditional bullet resistant glass, check here: [![](https://img.youtube.com/vi/RnUszxx2pYc/hqdefault.jpg "Surmet's ALON® Transparent Armor 50 Caliber Test") ](https://www.youtube.com/watch?v=RnUszxx2pYc) ---
**Author:** ![cochrane](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cochrane/32/10441_2.png) [@cochrane](https://boards.straightdope.com/u/cochrane)\ **Post date:** [October 26, 2014, 6:28pm UTC](https://boards.straightdope.com/t/is-transparent-aluminum-even-remotely-possible/702586/5 "2014-10-26T18:28:58Z")
From [Wikipedia](http://en.wikipedia.org/wiki/List_of_Star_Trek_materials#Transparent_aluminum): > [@](#): > > Pure transparent aluminum was created as a new state of matter by a team of scientists in 2009. A laser pulse removed an electron from every atom without disrupting the crystalline structure.[3] However, the transparent state lasted for only 40 femtoseconds, until electrons returned to the material. ---
**Author:** ![eltro102](https://avatars.discourse-cdn.com/v4/letter/e/7cd45c/32.png) [@eltro102](https://boards.straightdope.com/u/eltro102)\ **Post date:** [October 26, 2014, 6:41pm UTC](https://boards.straightdope.com/t/is-transparent-aluminum-even-remotely-possible/702586/6 "2014-10-26T18:41:51Z")
Aluminium Oxide makes transparent crystal ---
**Author:** ![eltro102](https://avatars.discourse-cdn.com/v4/letter/e/7cd45c/32.png) [@eltro102](https://boards.straightdope.com/u/eltro102)\ **Post date:** [October 26, 2014, 6:57pm UTC](https://boards.straightdope.com/t/is-transparent-aluminum-even-remotely-possible/702586/7 "2014-10-26T18:57:05Z")
(more commonly known as sapphires) ---
**Author:** ![picunurse](https://avatars.discourse-cdn.com/v4/letter/p/7bcc69/32.png) [@picunurse](https://boards.straightdope.com/u/picunurse)\ **Post date:** [October 26, 2014, 8:31pm UTC](https://boards.straightdope.com/t/is-transparent-aluminum-even-remotely-possible/702586/8 "2014-10-26T20:31:09Z")
Glass is just transparent sand…😃 Well, special sand (Modern day glass is 75% silica (SiO2) which comes from quartz in sand, plus 13% sodium oxide (Na2O) and 10.5% calcium oxide (CaO). Other minor additives include 1.3% aluminum oxide (Al2O3), 0.3% potassium oxide (K2O), 0.2% sulfur trioxide (SO3), 0.2% magnesium oxide (MgO), 0.04% iron(III) oxide (Fe2O3), and 0.01% titanium oxide (TiO2). ---
**Author:** ![njtt](https://avatars.discourse-cdn.com/v4/letter/n/ecd19e/32.png) [@njtt](https://boards.straightdope.com/u/njtt)\ **Post date:** [October 27, 2014, 6:03pm UTC](https://boards.straightdope.com/t/is-transparent-aluminum-even-remotely-possible/702586/9 "2014-10-27T18:03:49Z")
Calling aluminium oxynitride (or aluminium oxide) “transparent aluminium” is a bit like calling water “drinkable oxygen”. ---
**Author:** ![Learjeff](https://avatars.discourse-cdn.com/v4/letter/l/94ad74/32.png) [@Learjeff](https://boards.straightdope.com/u/Learjeff)\ **Post date:** [October 27, 2014, 6:32pm UTC](https://boards.straightdope.com/t/is-transparent-aluminum-even-remotely-possible/702586/10 "2014-10-27T18:32:10Z")
Well frankly, we wouldn’t even want transparent pure elemental aluminum. Aluminum isn’t very strong structurally unless alloyed. Yet we still often call things made of aluminum alloys “aluminum”, albeit, inaccurately. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [October 27, 2014, 6:34pm UTC](https://boards.straightdope.com/t/is-transparent-aluminum-even-remotely-possible/702586/11 "2014-10-27T18:34:50Z")
I have noticed that you can see through aluminized mylar. I assumed that was because the aluminum coating had enough holes in it too allow a very dimmed view through it when held close to the eyes. But I’ll ask anyway, is it possible that a thin enough layer of aluminum allows light to pass through? I’ll note that any aluminum exposed to the oxygen has a passivating layer of aluminum oxide on it, so to be transparent under normal circumstances that oxide would have to be transparent also. ---
**Author:** ![running\_coach](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/running_coach/32/15836_2.png) [@running\_coach](https://boards.straightdope.com/u/running_coach)\ **Post date:** [October 27, 2014, 6:40pm UTC](https://boards.straightdope.com/t/is-transparent-aluminum-even-remotely-possible/702586/12 "2014-10-27T18:40:12Z")
> [@Learjeff](#): > > Well frankly, we wouldn’t even want transparent pure elemental aluminum. Aluminum isn’t very strong structurally unless alloyed. Yet we still often call things made of aluminum alloys “aluminum”, albeit, inaccurately. And Derek Zoolander will have a new look; “Clear Steel”. ---
**Author:** ![jz78817](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jz78817/32/1028_2.png) [@jz78817](https://boards.straightdope.com/u/jz78817)\ **Post date:** [October 27, 2014, 6:51pm UTC](https://boards.straightdope.com/t/is-transparent-aluminum-even-remotely-possible/702586/13 "2014-10-27T18:51:22Z")
> [@TriPolar](#): > > I have noticed that you can see through aluminized mylar. I assumed that was because the aluminum coating had enough holes in it too allow a very dimmed view through it when held close to the eyes. But I’ll ask anyway, is it possible that a thin enough layer of aluminum allows light to pass through? sure. the shiny part of a CD is a thin vapor-deposited coating of aluminum. light passes through it. ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [October 27, 2014, 7:06pm UTC](https://boards.straightdope.com/t/is-transparent-aluminum-even-remotely-possible/702586/14 "2014-10-27T19:06:46Z")
I did an article on transparent metal for Optics and Photonics News some years ago. Very thin metals, like gold and silver, will actually transmit visible light, but we’;re talking about thicknesses like that of gold leaf. Alkali Metals (Lithium, sodium, potassium, cesium) are actually transparent in the ultraviolet, but for the heavier ones it edges up into the edge of the visible. Of course, they’re also highly reactive, so you’d want them sandwiched between quartz plates or something. In both these cases, there’s no weird or special circumstances needed. You’re not looking through vapor or plasma or anything, but through bulk metal (albeit not a lot of bulk). I’d also point out an article that appeared in Skeptical Inquirer several years ago where someone interpreted a story from Classical Rome about someone who had a malleable optical material as referring to aluminum. Although how someone in the classical world got a bulk sample of aluminum, or how they thought the aluminum was transparent is beyond me. In Hugo Gernsbach’s _Adventures of Ralph 124C41+_, Ralph (the fictional character, not the Doper) uses high frequency radio waves to see through solid metal. Gernsbach based his assertion on something he found in another technical magazine, but I haven’t been able to obtain a copy of that issue. Whatever it was, he obviously misinterpreted it, or else it was an enthusiastic and not very accurate report, because we don’t have anything like that now. ---
**Author:** ![Learjeff](https://avatars.discourse-cdn.com/v4/letter/l/94ad74/32.png) [@Learjeff](https://boards.straightdope.com/u/Learjeff)\ **Post date:** [October 27, 2014, 7:14pm UTC](https://boards.straightdope.com/t/is-transparent-aluminum-even-remotely-possible/702586/15 "2014-10-27T19:14:42Z")
So, what makes glass or water transparent? It’s not surprising to me that some materials reflect photons (some scattering them, others not), and others absorb them. Or, more accurately materials reflect some frequencies and absorb others. But what property makes it so it can pass right through? I suppose the question applies to gases, too, assuming it’s not the low density that makes them transparent. (Thanks!) ---
**Author:** ![njtt](https://avatars.discourse-cdn.com/v4/letter/n/ecd19e/32.png) [@njtt](https://boards.straightdope.com/u/njtt)\ **Post date:** [October 27, 2014, 7:20pm UTC](https://boards.straightdope.com/t/is-transparent-aluminum-even-remotely-possible/702586/16 "2014-10-27T19:20:01Z")
> [@Learjeff](#): > > Well frankly, we wouldn’t even want transparent pure elemental aluminum. Aluminum isn’t very strong structurally unless alloyed. Yet we still often call things made of aluminum alloys “aluminum”, albeit, inaccurately. Alloys are very different things from compounds. Aluminium oxynitride is not an alloy of aluminium, any more than water is an alloy, or mixture, of oxygen and hydrogen. ---
**Author:** ![Learjeff](https://avatars.discourse-cdn.com/v4/letter/l/94ad74/32.png) [@Learjeff](https://boards.straightdope.com/u/Learjeff)\ **Post date:** [October 27, 2014, 7:20pm UTC](https://boards.straightdope.com/t/is-transparent-aluminum-even-remotely-possible/702586/17 "2014-10-27T19:20:44Z")
Ah well, should have wiki’d first: > [@wiki](#): > > At the electronic level, absorption in the ultraviolet and visible (UV-Vis) portions of the spectrum depends on whether the electron orbitals are spaced (or “quantized”) such that they can absorb a quantum of light (or photon) of a specific frequency, and does not violate selection rules. For example, in most glasses, electrons have no available energy levels above them in range of that associated with visible light, or if they do, they violate selection rules, meaning there is no appreciable absorption in pure (undoped) glasses, making them ideal transparent materials for windows in buildings. > At the atomic or molecular level, physical absorption in the infrared portion of the spectrum depends on the frequencies of atomic or molecular vibrations or chemical bonds, and on selection rules. Nitrogen and oxygen are not greenhouse gases because there is no absorption because there is no molecular dipole moment. I think I get the idea: as long as the light doesn’t match the filtration allowed by the orbitals et al, it passes right through. If it matches, various things can happen (absorption, re-radiation, etc.) Feel free to elucidate. Based on that oversimplification, it’s just a matter of whether Al’s electrons can be coaxed into orbits with specific characteristics. Are there substances that are opaque unless combined in a mixture or alloy? Can alloys affect electron orbits? ---
**Author:** ![Learjeff](https://avatars.discourse-cdn.com/v4/letter/l/94ad74/32.png) [@Learjeff](https://boards.straightdope.com/u/Learjeff)\ **Post date:** [October 27, 2014, 7:22pm UTC](https://boards.straightdope.com/t/is-transparent-aluminum-even-remotely-possible/702586/18 "2014-10-27T19:22:05Z")
> [@njtt](#): > > Alloys are very different things from compounds. Aluminium oxynitride is not an alloy of aluminium, any more than water is an alloy, or mixture, of oxygen and hydrogen. Yes, I know. I should have said “for example”. But I bet we have compounds that get simplified in common language to the principle element too. Can’t think of any examples, so maybe I’m just plain wrong. ---
**Author:** ![Learjeff](https://avatars.discourse-cdn.com/v4/letter/l/94ad74/32.png) [@Learjeff](https://boards.straightdope.com/u/Learjeff)\ **Post date:** [October 27, 2014, 7:25pm UTC](https://boards.straightdope.com/t/is-transparent-aluminum-even-remotely-possible/702586/19 "2014-10-27T19:25:38Z")
Thinking out loud: metals have crystalline structure. Alloys have different crystalline structure than pure metals. Degrees of motion are a function of crystalline structure, and thus can affect transparency. Correct? But there’s still the selection rules at the electronic level … so much to learn, so little time! ---
**Author:** ![Bert\_Nobbins](https://avatars.discourse-cdn.com/v4/letter/b/aeb1de/32.png) [@Bert\_Nobbins](https://boards.straightdope.com/u/Bert_Nobbins)\ **Post date:** [October 27, 2014, 8:12pm UTC](https://boards.straightdope.com/t/is-transparent-aluminum-even-remotely-possible/702586/20 "2014-10-27T20:12:15Z")
> [@jz78817](#): > > sure. the shiny part of a CD is a thin vapor-deposited coating of aluminum. light passes through it. Completely untrue. The aluminium layer is there to reflect the laser light back to the photosensor. You do realise the data is on the TOP side of a CD? [Next page](https://boards.straightdope.com/t/is-transparent-aluminum-even-remotely-possible/702586.md?page=2)