Before this page was written, Vintage Radioactive Old lenses was the subject of two different posts during 2024.
I only now find the time to compile a text which is in part the synthesis and/or completion of these two posts, connected to this topic which has raised so much interest.
So let’s start with a bit of history. Not only speaking about photography…
Vintage radioactive old lenses
In the 1930s, powdered cream (THO-RADIA) were even produced which included RADIO.
Suppositories to improve sexual performance (VITA RADIUM) always with RADIO element.
Even a RADIO broadcaster! …which produced radioactive water.
(Image from: Commons Wikimedia)
License Attribution; Cinémagazine, 14 février 1935, CC BY-SA 4.0 https://creativecommons.org/licenses/by-sa/4.0, via Wikimedia Commons
It seems clear that the “fad” for radioactive products had spread at the beginning of the last century and had in some way infected our ancestors.
Studies relating to the atom, nuclear energy, and everything connected to it, had certainly contributed to the subject’s great media exposure. I don’t think it should be surprising at this point and in this historical context that lenses were designed and produced that used radioactive elements.
The element probably most used in the photographic field for the production of lenses was undoubtedly THORIUM, even if it was not the only one.
In the last century, besides thorium, other radioactive elements were used in the production of photographic lenses to improve their optical properties. The main elements are:
- Lanthanum: Although not inherently radioactive, it is important to mention because many glasses containing thorium also contained lanthanum oxide. This improved the refractive index and dispersive properties of the glass.
- Uranium: Uranium oxide was used in some glasses for photographic lenses, particularly during the 1940s and 1950s. This gave the glass a yellow or green tint and improved its optical properties.
- Potassium-40: Although present in minimal amounts and not intentionally added for optical purposes, natural potassium contains a small fraction of potassium-40, which is radioactive.
The use of these radioactive elements has been discontinued due to health and safety concerns related to radioactivity. Today, modern technologies and materials allow for the production of high-quality optical glass without the use of radioactive substances.
It’s interesting to understand the reason linked to my photographic passion. For which THORIUM was mainly added to Vintage Radioactive Old Lenses.
The reason is that THORIUM limits light reflections in the lenses. Thorium oxide was added to glass as it made it possible to create lenses with a high refractive index combined with low light dispersion.
Thorium glass was also used in ocular lenses for microscopes. Although in those quantities the thorium produced alpha and beta rays that the skin could easily shield. The same could not be said for the cornea of the eyes which could be damaged. Thorium lenses were produced between the 1940s and 1980s, but have since been banned.
I wanted to broaden my research into how THOTORIUM lenses were made, especially in the post-war period. I summarize here some information collected from internet sources, the veracity of which, although NOT totally proven, is at least largely reliable and logical.
Mechanical Processing
1. ** Glass Formation **:
– ** Melting **: Manufacturers melted raw materials, including thorium oxides and other glass components, in high-temperature furnaces to form a homogeneous mass.
– ** Molding **: They poured the melted mass into molds to create rough glass blocks.
2. ** Cutting and Shaping **:
– ** Cutting **: Workers cut the glass blocks into roughly sized discs.
– ** Shaping **: They used grinding tools to shape the discs into the desired form.
3. ** Polishing **:
– ** Coarse Grinding **: Initially, they ground the lenses with coarse abrasives to remove large amounts of material and achieve a general shape.
– ** Fine Grinding **: Then, they used finer abrasives to improve the shape precision and surface quality.
– ** Final Polishing **: Finally, they polished the lenses with fine abrasive pastes to achieve an optically transparent surface.
Chemical Treatments
1. ** Cleaning **:
– Technicians cleaned the lenses with specific chemical solutions to remove abrasive residues, oils, and other impurities.
2. ** Anti-Reflective Coatings ** (early 1950s):
– In the 1940s, anti-reflective coatings were not yet common, but they started to be applied in the 1950s.
– ** Coating Application **: They used vacuum deposition techniques to apply thin layers of anti-reflective materials.
Safety and Quality Control
1. ** Radioactivity Control **:
– In the 1940s, awareness of radioactivity risks was limited, so radioactivity control was less rigorous compared to modern standards.
2. ** Optical Inspection **:
– They inspected lenses optically to identify visual defects and ensure quality.
Conclusion:
During the 1940s, the processes for working and treating thorium-containing lenses included melting, cutting, shaping, grinding, polishing, and chemical cleaning. Anti-reflective coatings became more common in the 1950s. Awareness of radioactivity risks and safety practices were less developed compared to today.
