Quote:
Originally Posted by Stefan Buda
Unfortunately figuring is a bit of a black art that cannot be learned from books. It is very difficult to get a full size polishing lap to do exactly what you want it to do. The polishing pitch is a very viscous liquid that is exposed to various amounts of compression and dragging forces that make its behaviour rather unpredictable. A sub-diameter polishing lap is easier to predict but it is not as good at controlling astigmatism. Figuring is not as bad as sculpting because if you dig a hole somewhere, then you just have to polish away the rest of the surface until the hole disappears - not too hard for spherical surfaces but a nightmare for aspheric ones.
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I reckon it's a skill you must acquire during a lifetime doing it and start young too. Mentoring sounds like a necessary step as well. There are tools to do the job but in the end it's a very organic process and depends on the individual.