Oberon sent a reply this morning.
I wish we had the webpage from Mike Aurelius to find out his reasons and evidence for his opinion.
Oberon didn't exactly answer the questions. They sent a tech sheet and a brochure pdf. I'm not sure if I can include it here (copy and paste or attachment), so here are my interpretations:
Didymium-2 is an Oberon description. It was developed to reduce/eliminate sodium flare. As Mike Aurelius has pointed out, sodium flare is annoying, but not dangerous. Oberon states that it relies on the gold coating to reduce the IR and UV. In a previous thread (I don't remember when or what website) someone said that for soft glass workers, UV is not a concern because it is not emitted at the temperatures necessary for melting the higher COEs. (Not exactly what was said, which was more of a criticism for even including UV in the discussion.)
My guess is that the glasses are probably safe, but are hard to see through for detail work. The Didymium-2 does not provide the protection we need and Oberon does not claim it does, but claims that it uses the gold coating to do so.
From the brochure (transcription, because text does not want to copy and paste):
OBERON's Didymium II Fact Fit(R) Shield for glass manufacturing or glassblowing, especially when a gas (propane) powered furnace is used. The shield provides a filter which selectively blocks the yellowish light at 589 nm (nanometers) emitted by the hot sodium in the glass, without having a detrimental effect on general vision, unlike dark welder's glasses. In addition, blocked is the strong ultraviolet light emitted by the superheated furnace gases and insulation lining the furnace walls thereby sasving the individual's eyes from serious cumulative damage. The gold coating glocks 94-96% of the infrared radiant energy to keep the wearer's face cool.
From the fax copy:
The Heat Reflective Faceshield is very efficient in reflecting away UV and IR (radiant heat). Oberon vacuum deposits a layer of pure GOLD (24K) on the outer surface of the polycarbonate shield. This is not a film but a permanently bonded lalyer upon the shield. The GOLD layer is then protected with a thermally inert scratch coating. ...
...
Statistics
UV <1%
Visible ±15%
IR <10%
...
Didymium Blue-2
Material: Polycarbonate
Color: Didymium Blue
Specialty coating: Gold metalized
Meets ANSI Z87.1: Yes
Group description
Oberon has developed an alternative to the didymium glass lens. The Face-Fit (tm) Didymium-2 Blue shield is molded of strong polycarbonate material. Providing similar visible light filtering characteristics as the didymium glass lens, it allow (sic) for greater visibility of the work place through its 8" X 14" window.
Filtering out the yellow glare associated with glass working operations, it allows the worker to see the reds associated with temperatures and heats. Oberon's specialty gold heat reflective layer coats the shield with additional heat (IR) and UV protection not available from standard didymium lenses.
Workers who are looking into open flames use the Didymium products. This flame is emitting IR and UV radiation. Didymium glass lenses are not designed to provide protection from this radiation. Its purpose is to filter out the yellows in the visible spectrum. Oberon believes where the potential for hazards of UV and IR exposure exist, it is important to provide the best protection available. The gold metalized layer on the didymium substrate acts to reflect and filter most of the UV and IR before it reaches the wearer.
...
For comparison, here are descriptions for the faceshields (to evaluate the gold coating itself without the didymium):
FF-025 Clear gold reflective: UV & IR protection while maximizing visible light. IR protection required in high heat application such as Steel Mills and foundries.
FF-091 Didymium II gold reflective: UV and IR protection for the Glassworker, the Didymium filters out the yellow but allows much of the reds (glass temperature) to be seen.
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