The optical manufacturer normally purchases bulk optical glass in a form identified as a strip. The optical manufacture companies are with a very predictable &reliable product and provide us with thorough information about the optical & mechanical properties of any glass that we purchase. A blank for the spherical lens will be one disc with a flat top and bottom. A blank for cylindrical lenses will be with a rectangular cross-section. The bar is made into multiple identical components.
The Components with a constant radius of curvature can be produced through all means in generating, grinding, and polishing. Alternatively, the components can be made using two steps: generating and polishing, which among them accomplish the grinding function. For components with a non-constant radius, the two-step method is used.
When a lens is not being produced through equipment, it is common to use finer liquid abrasive slurry solutions to slowly make the glass surface somewhat smooth. The appearance of the glass surface fluctuates as the texture gets fine but the surface is still noticeably gray, after grinding.
The grinding processes
The grinding does not change the curving of the lens exterior. Grinding makes the lens slightly thinner, which is why the preceding generating step leaves a little extra thickness. Grinding is a faster process, usually requiring only fewer minutes per surface. Grinding uses a rotary table with a physically operated swing arm to position the grinding tool contrary to the lens surface. The Polishing process uses liquid abrasive slurry to smooth the frosted glass texture until the surface is smooth and transparent. The polishing pad in a polisher is made from a material that looks like a fine mesh sponge or a coarse cloth. The polishing pad is made from the pitch that is scored to let the liquid abrasive slurry infiltrate between the pitch & the glass surface.