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.