What types of glass are there?
1. Soda glass or soda-lime prepared by heating sodium carbonate and silica.
2. Coloured glass: with the addition of metallic oxides
3. Plate glass: Thicker than ordinary glass.
4. Safety glass: Made by placing a sheet of plastic such as celluloid between sheets of glass.
5. Laminated glass: Several layers of safety glass are bound together with a transparent adhesive.
6. Optical glass: Potassium and lead silicates are used in making optical glass.
7. Pyrex glass: The addition of boron oxide creates a high melting point and is resistant to many chemicals.
8. Photo-chromatic glass: silver iodide gets coloured with the intensity of light.)
9. Lead crystal glass: adds lead oxide in crystal glass
In Spectacles nowadays glass is rarely used but rather plastics in a range of indexes for the best aesthetics and optics, balancing weight, thickness, and optical quality
Glasses can be made for one vision purpose or multiple purposes depending upon the lens design and placement in the frame
Coatings and materials to enhance vision and enable comfort and safety abound.
Why would you want to? Lightweight tailor made options exist.
The Varilux progressive lens was first introduced by Bernard Maitenaz in 1959,enabling clear distance vision on upgaze versus reading vision and in between on downgaze.
