Memory Beta, the wiki for licensed Star Trek content.

Transparent aluminum is a transparent material that was much stronger and lighter than plexiglass. While plexiglass sheets for a 60x10 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 1986, a time traveling Montgomery Scott gave the formula to Dr. 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.

The RPG sourcebook 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 short story: "The Music Between the Notes")

On Federation starships, the windows were usually made of transparent aluminum rather than glass. (TNG episode: "In Theory", DS9 short story: "Requital")

External Links

• Transparent aluminum article at Memory Alpha, the wiki for canon Star Trek.
• Transparent aluminum article at Wikipedia, the free encyclopedia.