Filter glass types

[Rickjs]

What is, if any, the difference between filters using optical glass and those that use Schott glass?

 

[KmH]

Schott glass is a higher grade of optical glass.
Schott AG is a company founded by - "The glass chemist Otto Schott laid the foundation for modern glass science and technology in Jena back in 1884. Together with the congenial Ernst Abbe, Carl Zeiss and his son Roderich Zeiss, he founded the Glastechnisches Laboratorium Schott & Genossen, which would later become Jenaer Glaswerke Schott & Genossen and the today Schott AG." Schott AG - Wikipedia, the free encyclopedia

Glass Manufacturers | SCHOTT North America | SCHOTT North America

Cheap, and some not so cheap, filters use good 'ol regular window glass that is not optically clear, nor optically flat, and not as robust as Schott glass.

 

[budget cruncher]

Schott also makes wine glasses, FWIW.

 

[Watchful]

Schott glass is made from melted silica sand and a few additives.
Other glass is made from silica sand and a few additives.
The main difference is in the treating, heating, cooling, grinding and polishing that is done after its created.
Surface defects exsist in all glass, they can only be minimized. All glass has opacity and an index of refraction that changes with temperature.
Some claim that glass is a highly viscous liquid and will deform over time. Others say it is neither liquid nor solid and is instead a different and unique state of material.

 

[petrochemist119 144]

Schott is a manufacturer of Glass. They make a very large range of glasses, (almost certainly 100's of types) some of which are opaque to visual wavelengths. I have at least 15 of their technical glasses for wavelength selection (IR & UV photography).
I don't know the technical specification for 'optical glass' but I suspect it involves the uniformity of the glass, inclusions, bubbles, etc.

Most of my Schott glass filters are not AFAIK specified to optical grade, the image recorded through them may not be quite as sharp as images taken through optical grade R72 (Hoya IR filter roughly equivalent to the Schott RG695 & RG9 I have).

 

[Watchful]

Schott was never reported to be the best glass company, just another glass manufacturer. The company with the best technology and perhaps the finest glass made is Corning. They made the ultra low expansion (ULE) glass mirror blank for the Hubble telescope. Remember the one that needed costar added to it to be able to see? The defect in the mirror was due to the finishing done by Perkins-Elmer, who used incorrect specifications provided by NASA and not a flaw in the glass.