Transparent aluminum is a fictional material in the Star Trek universe which was introduced in the movie Star Trek IV: The Voyage Home (1986).
Transparent aluminum is sometimes confused with transparent alumina, a transparent ceramic composed of alumina (aluminum oxide).
Appearance in Star Trek
The chemical formula for transparent aluminum plays a key role in the plot of Star Trek IV: The Voyage Home. In the movie, the formula is traded for Plexiglas sheets thick enough to create water tanks suitable for transporting two humpback whales through time, from the 20th century to the 23rd century, inside a Klingon Bird of Prey. Since the crew was temporarily stranded in the past without money appropriate to the period, they had to barter with the owner of the Plexicorp company (a fictional manufacturer of Plexiglas). Scotty trades the chemical formula for transparent aluminum for enough of the material to build the tanks.
Star Trek technical manuals allege transparent aluminum to be used in various internal fittings in starships, where the sets include what appears to be glass. However, such fittings have been observed to shatter in the manner of toughened glass.