Transparent aluminum is a transparent material that was much stronger and lighter than plexiglass. While plexiglass sheets for a 60 by 10 tank with 18,000 cubic feet of water would need to be six inches thick, a transparent aluminum sheet would only need to be one inch thick.
In the year 1986, a time traveling Montgomery Scott gave the formula to Doctor. Marcus Nichols in exchange for plexiglass to enclose a tank on board the HMS Bounty in order to transport the humpback whales George and Gracie to the 23rd century. Nichols was eventually recognized as the inventor of transparent aluminum. (TOS movie: Star Trek IV: The Voyage Home)
- In the novelization, this incident was portrayed as less haphazard than the same sequence in the movie: Nichols was established to have a materials research background, and Scotty recognized his name (as readily as McCoy would Pasteur) from engineering history as the inventor of transparent aluminum as well as a number of other things.
- Spock cited that year during a memory test on Vulcan prior to the events of The Voyage Home. The Last Unicorn RPG module: All Our Yesterdays: The Time Travel Sourcebook gives the actual "invention" date as 1986.
Space stations such as Deep Space 9, Starbase 1 and Pelios Station use transparent aluminum in their windows. (DS9 reference: Star Trek: Deep Space Nine Technical Manual; DS9 novel: Time's Enemy; DS9 - The Lives of Dax short story: "The Music Between the Notes")