Originally Posted by grup
The writers weren't too concerned about altering his in ST-TVH when Scottty gave away the formula for transparent aluminum.
According to the novelization of the movie, Scotty purposely gave the formula to the man who would discover transparent aluminum anyway: Dr Nichols. In the movie it was made humorous to keep the mood light. In the novel, McCoy doesn't smile and nod when Scotty says "How do we know he didn't invent the thing" because he's not an engineer and he doesn't get the joke. McCoy presses Scotty for an explanation at which point the engineer patiently explains why he gave the matrix to Dr Nichols. In this way Scotty gets the materials he needs to complete his mission and the right person still invents transparent aluminum, maybe just a little bit faster than history had originally planned.