Andrea Sella - Glassblowing and Didymium Glasses 

very sneaky, thanks for the tip..lol

Thank you Magatherium, as a scientific glassblower for over 40 years (now retired), you'd be amazed at the stuff we made, designed, and fixed all without any credit. Think of the number of chemists out there who relied upon their glassblower to make their chemistry happen only to not even get a comment of gratitude in the resulting paper.

Nobody had to think to combine the two elements! Didymium was actually discovered *before* praesodymium and neodymium - the two are so chemically similar that they pretty much always occur together in nature, and were difficult for chemists to separate or even tell apart at first. When first discovered, didymium was originally thought to be a *single* new element, atomic symbol Di, and was only later determined to actually be a mixture of two new elements.

Nobody had to think to combine the two elements! Didymium was actually discovered *before* praesodymium and neodymium - the two are so chemically similar that they pretty much always occur together in nature, and were difficult for chemists to separate or even tell apart at first. When first discovered, didymium was originally thought to be a *single* new element, atomic symbol Di, and was only later determined to actually be a mixture of two new elements.

Neil Camara actually it was very useful for astronomers back when sodium street lights were more popular

Cobalt glasses only decreased the amount of light coming through they do not filter the sodium wavelength. For brazing you want less light reaching your eyes, there is no specific frequency wavelength to be concerned about.

With due respect, have you ever tried cobalt classes? 🤔 (I have) They do block the 590 nm wavelenght light (yellow) emitted from sodium. Besides, infrared radiation can cause eye damage on the long term, welding and brazing glasses are specifically made to shield from excessive light and most of IR waves.

@@BartolomeoPestalozzi444 Yes I have. I was a glassblower for over 40 years and used and/or tried a variety of different eye protection. I used some cobalt glasses for a long time for quartz work until I found a better solution. Yes, they do cut down the amount of light as well as the IR range (which is important for quartz work) but do not cut down the sodium frequency as well as your standard didymium lenses. Regular borosilicate glass does not emit anywhere near the amount of IR radiation as quartz.

It would not cancel out light pollution at all. Just one section of the wavelength.

That's brilliant.

Bad idea. It would lead to firefighters getting into very bad situations because they could not see flames. I understand that it might help in see through flames, but I want to know where the fire is so I can predict it's behavior and not being able to see flames would preclude that. Thermal imaging makes much more sense.

Blitz350 Just one question, how do thermal imaging helps in a building with fire?, I think you wouldnt be able to even see a person, because the IR will be saturated with the intense heat of the fire. Also you could have just half of your vision with that kind of glass, or a mixture of both that does not fully block the flames, then you will be able to se through fire and know where the flames are.

That is a pontential situation with a TIC but rarely happens. Part of a how a TIC works is based on an objects transmission and reflection of IR radiation and a group of objects at the same temp will rarely have identical rates of transmission and reflection. It was a bigger issue with older TIC's. Newer ones have much better detectors and screens to allow for higher definition to avoid complete wash out.

charlie lange There is a difference between sodium emission and the emission from carbon particles from a fire. The sodium emission has a couple of emission lines in the yellow that is very intense. The emission from a fire has more of a blackbody radiation spectrum (full spectrum).

Dark.

@@yohaijohn Only if they're low pressure sodium, and that's so rare nowdays. High pressure sodium is used, and in those, mercury glows, too. So it wouldn't be dark, but darker, sure.

The glare of the sun has nothing at all to do with Sodium emission... you'd still go blind!

The sun produces more wavelengths and 10,000 lumens, much more than glass. You need a lens shade 10 at least to stare safely at the sun. Didymium alone also doesn't provide IR protection.