crown process

The user is asking about the "crown process" in an industrial context. The provided search results discuss two distinct topics: "prosthodontics" and "crown glass." The term "crown process" specifically refers to the historical method of manufacturing crown glass.

Crown Glass Manufacturing

The crown process was a technique for creating handmade soda-lime glass, primarily used for glazing and optical purposes. This method involved blowing a bubble of glass into a pear shape, then flattening it. The bubble was transferred to a solid iron rod, reheated, and spun at high speed. Centrifugal force expanded the glass into a large, circular plate, up to 60 inches in diameter. The resulting "table" of glass was thin, lustrous, and featured concentric ripple lines from the spinning. A characteristic feature was the "bull's eye" in the center, a thickened area where the rod was attached, which was sometimes considered a defect but later prized for its antiquity.1

This process was popular for its superior quality and clarity, especially when compared to cheaper cylinder glass. While it was gradually replaced by easier methods for larger glass sheets from the mid-17th century, it was used in the U.S. until around 1827. Crown glass's optical properties made it valuable for lenses, particularly when combined with flint glass to correct chromatic aberration.1