# Transparent aluminum **URL:** \ **Category:** Miscellaneous and Personal Stuff I Must Share\ **Created:** [February 21, 2018, 2:57am UTC](https://boards.straightdope.com/t/transparent-aluminum/809245 "2018-02-21T02:57:38Z")\ **Posts on this page:** 14\ **Page:** 2
**Author:** ![gnoitall](https://avatars.discourse-cdn.com/v4/letter/g/bb73d2/32.png) [@gnoitall](https://boards.straightdope.com/u/gnoitall)\ **Post date:** [February 22, 2018, 6:59pm UTC](https://boards.straightdope.com/t/transparent-aluminum/809245/21 "2018-02-22T18:59:57Z")
> [@TriPolar](#): > > Right. Those are other examples of transparent aluminum. What’s your problem with this? There’s a aluminum in it and you can see through it, it’s transparent aluminum. I hope you remember that when you buy windows. Insist on the finest transparent silicon. ---
**Author:** ![Dave.B](https://avatars.discourse-cdn.com/v4/letter/d/9f8e36/32.png) [@Dave.B](https://boards.straightdope.com/u/Dave.B)\ **Post date:** [February 22, 2018, 7:12pm UTC](https://boards.straightdope.com/t/transparent-aluminum/809245/22 "2018-02-22T19:12:03Z")
> [@gnoitall](#): > > Think about it. A critical moment of dialogue depended UTTERLY on the transparency of the tank walls.It just doesn’t work if Scotty can’t see into the tank. “Admiral, I think there be whales here. Yaar.” > > The tank had to be transparent; otherwise (A) you don’t get to see a nice CG transporter effect, and (B) Scotty has to say something not inane. “Admiral, sensors indicate there be whales here”. But fair enough. 😃 ---
**Author:** ![Inigo\_Montoya](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/inigo_montoya/32/124_2.png) [@Inigo\_Montoya](https://boards.straightdope.com/u/Inigo_Montoya)\ **Post date:** [February 22, 2018, 7:25pm UTC](https://boards.straightdope.com/t/transparent-aluminum/809245/23 "2018-02-22T19:25:15Z")
> [@](#): > > SCOTT: How thick would a piece of your plexiglass need to be, at sixty feet by ten feet to withstand the pressure of eighteen thousand cubic feet of water? > NICHOLS: That’s easy, six inches. We carry stuff that big in stock. > SCOTT: Aye, I’ve noticed. Now suppose, …just suppose, …I was to show you a way to manufacture a wall that would do the same job but be only one inch thick. Would that be worth something to you, eh? So they need a piece of polycarbonate 15.24m x 18.28m x 15.24cm. That weighs 10,200kg A similar piece of aluminum would be 22,560 kg A similar piece of glass would be 49,757kg I’ll defer to an engineer type on the following, but it is my understanding: - polycarbonate would be stronger and more durable than glass. Given glass weighs about 5x more and is both weaker and more brittle, Scotty don’t want to use glass. - 1980s steel or aluminum would at best be comparable in strength to PC, but it is not transparent (which is nice, and they really need to traumatize the beasties as little as possible) and a big unplanned honkin slab of metal could conceivably interfere with the ship’s navigation sensors and cloaking device. Suboptimal complications to the mission. Plus, they’re in a hurry and they know of a place near their base of operations with a suitable material for their purposes–they could shop around for just the right thing, but this place has something that is good enough and available right now. But this is all academic, right? We don’t know if Scotty’s buying polycarbonate or acrylic (which is not nearly as rugged). ETA: I f-ed up the dimensions, should be 3.05m x 18.28m x 15.24cm. But the relative weights should bear out the rest of the post ---
**Author:** ![gnoitall](https://avatars.discourse-cdn.com/v4/letter/g/bb73d2/32.png) [@gnoitall](https://boards.straightdope.com/u/gnoitall)\ **Post date:** [February 22, 2018, 8:28pm UTC](https://boards.straightdope.com/t/transparent-aluminum/809245/24 "2018-02-22T20:28:07Z")
> [@B-Rad](#): > > So they need a piece of polycarbonate 15.24m x 18.28m x 15.24cm. That weighs 10,200kg > A similar piece of aluminum would be 22,560 kg > A similar piece of glass would be 49,757kg > > I’ll defer to an engineer type on the following, but it is my understanding: > > - polycarbonate would be stronger and more durable than glass. Given glass weighs about 5x more and is both weaker and more brittle, Scotty don’t want to use glass. > - 1980s steel or aluminum would at best be comparable in strength to PC, but it is not transparent (which is nice, and they really need to traumatize the beasties as little as possible) and a big unplanned honkin slab of metal could conceivably interfere with the ship’s navigation sensors and cloaking device. Suboptimal complications to the mission. Plus, they’re in a hurry and they know of a place near their base of operations with a suitable material for their purposes–they could shop around for just the right thing, but this place has something that is good enough and available right now. > > But this is all academic, right? We don’t know if Scotty’s buying polycarbonate or acrylic (which is not nearly as rugged). > > ETA: I f-ed up the dimensions, should be 3.05m x 18.28m x 15.24cm. But the relative weights should bear out the rest of the post The problem is that the movie assumed we’d have different thicknesses of material depending on strength. But I’ll just point out that aluminum oxynitride is half again as dense as crown glass (3.7 g/cm[sup]3[/sup] versus 2.4 g/cm[sup]3[/sup]). I don’t know how much stronger it is than glass that you could reduce thickness, but starting out 50% heavier for the same dimensions is quite a disadvantage. ---
**Author:** ![Inigo\_Montoya](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/inigo_montoya/32/124_2.png) [@Inigo\_Montoya](https://boards.straightdope.com/u/Inigo_Montoya)\ **Post date:** [February 22, 2018, 8:38pm UTC](https://boards.straightdope.com/t/transparent-aluminum/809245/25 "2018-02-22T20:38:32Z")
gnoted. (I promise not to do that again). ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [February 22, 2018, 10:46pm UTC](https://boards.straightdope.com/t/transparent-aluminum/809245/26 "2018-02-22T22:46:26Z")
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**Author:** ![Just\_Asking\_Questions](https://avatars.discourse-cdn.com/v4/letter/j/ba9def/32.png) [@Just\_Asking\_Questions](https://boards.straightdope.com/u/Just_Asking_Questions)\ **Post date:** [February 22, 2018, 10:59pm UTC](https://boards.straightdope.com/t/transparent-aluminum/809245/27 "2018-02-22T22:59:56Z")
FWIW I agree with DaveB ever since my one and only viewing of this film when it was new. There’s no reason the tank has to be transparent. None. Plus, it’s all academic. As soon as the whales are released, they are going to tell the alien probe 'humans killed us all off! DESTROY THEM!" and that will be that. ---
**Author:** ![Enola\_Straight](https://avatars.discourse-cdn.com/v4/letter/e/dec6dc/32.png) [@Enola\_Straight](https://boards.straightdope.com/u/Enola_Straight)\ **Post date:** [February 23, 2018, 3:05am UTC](https://boards.straightdope.com/t/transparent-aluminum/809245/28 "2018-02-23T03:05:36Z")
> [@Dave.B](#): > > Something that has always bothered me about the film: why was it so important that the walls of the whale tank were transparent? It was so important that Scotty was willing to change history and give out the formula for transparent alumin **i** um. > Why not just make it out of regular opaque alumin **i** um? Subtle fnord technique, grasshopper. ---
**Author:** ![Napier](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Napier](https://boards.straightdope.com/u/Napier)\ **Post date:** [February 25, 2018, 10:41pm UTC](https://boards.straightdope.com/t/transparent-aluminum/809245/29 "2018-02-25T22:41:52Z")
> [@rbroome](#): > > I was fascinated when I first read this. I read up on the substance and realized that it had in fact been invented back in the 70s and is still under patent to one company. Clearly a commercial product and clearly the owners have decided that low sales works for them. Otherwise we would have it in everyone’s car windows by now! 🙂 > > As I gather from reading, one basic limitation is that it is so hard it is difficult to polish properly-raising it’s costs. Patents only last 20 years. Anything invented in the 70’s has been available to everybody to practice since at least 2000. If it was worth putting in car windows it would be there. ---
**Author:** ![Napier](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Napier](https://boards.straightdope.com/u/Napier)\ **Post date:** [February 25, 2018, 10:47pm UTC](https://boards.straightdope.com/t/transparent-aluminum/809245/30 "2018-02-25T22:47:57Z")
A little web searching shows that it’s a commercial product but not all that successful, more of a niche product. Basically it is very hard and impact resistant, and is fairly similar to sapphire as a window material according to vendors, but reduces the cost by about 40%. Especially, it seems good at withstanding impact without shattering. I’ve used sapphire windows made by several companies for a variety of laboratory and industrial purposes over the years, and have never heard of this stuff. It doesn’t appear very popular. ---
**Author:** ![glowacks](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/glowacks/32/5548_2.png) [@glowacks](https://boards.straightdope.com/u/glowacks)\ **Post date:** [March 5, 2018, 12:39am UTC](https://boards.straightdope.com/t/transparent-aluminum/809245/31 "2018-03-05T00:39:00Z")
Uh, they didn’t _use_ transparent aluminum to hold the whales; they traded its formula for some currently-available plexiglass. One of the most brilliant lines I think ever written was when Scotty asked the guy how much of his stuff it would take to hold what he was planning on holding, not only to use that as the basis for how much he needed, but also to be able to brag how much superior the substance was whose formula he was about to give them. ---
**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:** [March 5, 2018, 3:07am UTC](https://boards.straightdope.com/t/transparent-aluminum/809245/32 "2018-03-05T03:07:18Z")
Right. Nobody here said they used transparent aluminum in the movie. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [March 5, 2018, 3:21am UTC](https://boards.straightdope.com/t/transparent-aluminum/809245/33 "2018-03-05T03:21:47Z")
Hence also why the guy mentioned that they had the required material off-the-shelf, to account for the heroes being able to get ahold of it in a hurry. **B-Rad** , is polycarbonate ever referred to as “plexiglass”? In my experience, that word always and only ever refers to acrylic. ---
**Author:** ![Napier](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Napier](https://boards.straightdope.com/u/Napier)\ **Post date:** [March 5, 2018, 5:18pm UTC](https://boards.straightdope.com/t/transparent-aluminum/809245/34 "2018-03-05T17:18:03Z")
> [@Chronos](#): > > […] > > **B-Rad** , is polycarbonate ever referred to as “plexiglass”? In my experience, that word always and only ever refers to acrylic. “Plexiglas” (uppercase “P” and one “s”) is a brand name for acrylic sheet. Some consider “plexiglass” a generic term for acrylic sheet. Polycarbonate sheet is sold under the brand name “Lexan”. I’m sure there are other brands for both polymers. How individuals may use and misuse the brands is, of course, up for grabs. [Previous page](https://boards.straightdope.com/t/transparent-aluminum/809245.md?page=1)