For the most part, optical glass is offered in large blocks, stripes and gobs by the primary optical glass manufacturers. Most of the primary manufacturers are listed in the compendium.
The material made by the primary manufacturers is either cut up to yield the desire blanks or it goes through a secondary molding operation to produce a blank. The cut or molded blanks are then ground and polished to yield the optics desired.
Optical glass is a dense material (heavy per cubic inch) and can cost from a few dollars per pound to hundreds of dollars per pound. Therefore, usually molded blanks result in a cost savings over cut blanks. This is because there is higher waste factor associated with cutting a blank out of a larger piece of material rather then what is required to mold the same blank. However, this does not hold true for a limited number of optical glasses that have a very high expansion coefficient and do not lend themselves to being molded easily. For very high expansion type glasses, it may be safer to have them cut out of the primary material.
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