I thought the 10 month cooling period to anneal the blank was incredible, but then I read it took 13 years to grind and polish away 4½ tons of glass to make it

I thought the 10 month cooling period to anneal the blank was incredible, but then I read it took 13 years to grind and polish away 4½ tons of glass to make it parabolic (originally estimated to take 7 years). Project of a generation!