What type of glass is known for its general excellence in spectacle lenses?

Crown glass is widely recognized for its general excellence in spectacle lenses due to several key characteristics. Firstly, it has excellent optical clarity, which is crucial for providing a clear and undistorted vision. This makes it a preferred material for prescription eyewear, as it enhances the wearer’s visual experience.

In addition, crown glass has good scratch resistance, which helps maintain the quality of the lenses over time. It also provides adequate rigidity, allowing for durability while remaining lightweight. Furthermore, crown glass can be easily polished to a fine finish, contributing to its overall aesthetic appeal, which is an important factor in the selection of eyewear.

While polycarbonate is celebrated for its impact resistance and lightweight properties, it may not match the optical clarity of crown glass. Borosilicate glass and fused silica are used in specific applications, such as laboratory glassware or optical components requiring thermal resistance or clarity at extreme temperatures, but they are not commonly preferred for regular spectacle lenses due to their weight or additional properties that may not be necessary in eyewear.

Overall, crown glass remains a classic choice in the industry, celebrated for its optical quality and suitability for everyday use as spectacle lenses.