CZ JENA 1900 - Looking for air bubbles?

[Steven Tribe]

Not much on history lately, so I thought I would post a photo from that site (200532694840). Quite a lot of optical glass slabs.
This is so special an item that I am sure this will not influence bidding!
I have absolutely no knowledge of the lister.

[Lynn Jones]

Mostly they were looking for inclusions (ugly specs) and to a lesser extent huge bubbles. All optical glasses had small bubbles (they didn't afftect the quality of the lens). Until the 1950's, the Japanese discovered that when re-melting the high quality optical glasses in order to add needed chemicals, if they were doing this in platinum covered crucibles and stirrers there would be no bubbles.

Those of us who were adult in those days would reject lenses without bubbles as not being good enough, then later we had judge glasses without bubbles, drove us all nuts because then we had to guess whether the lenses were old enough to be good with bubbles or new enough not to have bubbles.

It's never easy is it.

Lynn

[domaz]

Those of us who were adult in those days would reject lenses without bubbles as not being good enough, then later we had judge glasses without bubbles, drove us all nuts because then we had to guess whether the lenses were old enough to be good with bubbles or new enough not to have bubbles.


Lynn-

Why were lenses with bubbles considered good in those days? I've heard this many time and always wondered the reason.

[Steven Tribe]

I didn't seriously think they were looking for tiny air bubbles. Glass is a wonderously complex material and only the worst faults could be found by these experienced gentlemen at Zeiss.

There are threads here about pros/cons of air bubbles!

I am surprised by the selling price of these slides. Although the seller said they have not been published, the slides are labelled Ed. Liesegang who probably still hold the copyright for reproduction. They were still a direct competitor to Zeiss at the time these factory images were made.

[CCHarrison]

Attached is what Taylor-Hobson had to say about bubbles in the 1920's...

Dan

[Lynn Jones]

To Domaz,

The reasoning for pre-mid-1950's lenses with tiny bubbles was that quality optical glasses simply couldn't be made without bubbles but window glass could be without bubbles. I've been a photographer since the late 1940's, good quality lenses always had tiney bubbles in those days, cheap box camea lenses and window glass did not.

Lynn