Transparent Metal (Hydroxide) Without Mr. Scott

There’s a famous scene in one of the Star Trek movies where Scotty, who has traveled to the past, teaches a metal company to create the transparent aluminum he needs to bring some whales back to the future. But [The Action Lab] shows that we already have see-through metal, just not aluminum. You can see a video about why metals are normally opaque.

The metal in question is sodium. Normally, it isn’t transparent, but molten sodium hydroxide does turn transparent after it — well, sort of explodes. Of course, sodium hydroxide isn’t really a metal, but then neither is the aluminum oxide that’s been touted as real transparent aluminum. Aluminum oxide also makes transparent gemstones like rubies. However, there is some — kind of — transparent aluminum at the end of the video.

The thin aluminum film on a plastic substrate probably won’t hold a whale, though.  It isn’t totally transparent, either. The material looks like a mirror, but a laser on one side will make a partial appearance on the other side.

What’s interesting here, though, is the explanation about why metals aren’t normally transparent. Well, that, and exploding sodium.

We’ve looked at so-called transparent aluminum before. We’ve also seen apparently transparent metal that uses a mysterious trick.

24 thoughts on “Transparent Metal (Hydroxide) Without Mr. Scott

  1. “In one of the Star Trek movies”. Either you know we all know the movie (by heart), or you want us to “an educated guess”.

    Mr. Scott cannot give me exact figures, Admiral, so… I will make a guess.
    A guess? You, Spock? That’s extraordinary.

    1. They didn’t have transparent alumin[i]um, so Mr. Scott traded the formula for a large plastic sheet.
      “I see you’re still using polymers…”

      “A keyboard? How quaint!”

    2. Perhaps it is time for a “colorful metaphor”?

      Excuse me… excuse me! We are looking for the nuclear wessels. At Alameda.

      Admiral! There be whales here!

      Me? I’m from Iowa, I only work in outer space.

      It’s his “way”. He did a lot of LDS in the sixties.

      1. It’s called AlON (Aluminium oxynitride) AKA “synthetic sapphire” or “synthetic ruby”. The sapphire and ruby versions are grown as crystals and have dopants to colour them, the clear version is used for “sapphire glass” watch crystals and a sintered version (commercially known as ALON) used in windows for armoured vehicles.
        Synthetic ruby and sapphire was developed in 1902 by a French chemist, Auguste Verneuil.
        ALON was patented in 1980 by JW McCauley, thus “transparent aluminium” predates the release of “ST: The Voyage Home” by six years.

  2. I would said that the aluminium sheet is translucid rather than transparent, since you can’t really see completely through (transparent), but you can have a small fraction of light that can go through.

  3. “A thin layer will kinda let some laser light through” is a very low bar for ‘transparency’. Pretty much any metal will display that sort of incomplete opacity in sufficiently thin layers.

    1. A thin enough sheet of anything will let light through. Or more accurately the quantum uncertainty of the exact location of the photons allows them to basically ignore any barrier if it’s thin enough.

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