Cannot remember the title or author of this fantasy book. Scientist invented a machine that landed them in an alternate world in the field of a dwarf who had been trying to find the recipe for aluminum so he is considered an official Wizard. The scientist also helps a knight by putting ground polished glass in his helmet so he can see. This was a very funny book.
Let's see, the dwarf is a leprechaun, the knight is a nearly blind bandit that 'Brewster Doc' makes lenses for, and aluminum is the Philosopher's Stone.