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Comment by nickt | Hacker News Reader

This video and reading the recent article referencing Brimar valves (of the vacuum tube variety) [1] led me down the rabbit hole of, how hard can it be to make a few CRTs. Despite growing up with them, it turns out I had no idea. Lots of ovens and nasty chemicals involved - see for yourself in this great old video [2]. I wonder if anyone in the retro scene is eccentric and rich enough to give it a go…

[1] https://brimaruk.com/

[2] https://youtu.be/32yYfTVIzBE

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I remember hearing the main issue is that the glass is made up of a significant amount of led so even if it was commercially feasible it would be legally impossible to sell, import or manufacture new CRT tubes due to the regulations many developed nations have in place.

How are car batteries sold, imported, or manufactured?

That was the explanation I was given when asked.

I imagine different regulations apply to different products. Also obviously different countries have different regulations.

Lead makes up 20-25% of the contents of the glass of a CRT tube so I imagine that restrictions like those listed in the link below would cause issues.

https://dtsc.ca.gov/restrictions-on-the-use-of-certain-hazar...

There are exemption. And if you think of it, it is a lot easier to properly dispose and recycle the plates in a car battery than in electronics solder or glass.

I can't speak for any other regulations, but the EU's RoHS has a specific exemption for lead in the glass of cathode ray tubes.

CRTs are still being actively manufactured, primarily for avionics and military applications.

https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX%3A...

https://www.thomaselectronics.com/manufacturers/

https://moores-glass.co.uk/products/cathode-ray-tubes/

Fantastic, thank-you. Every day continues to be a school day!

Lead glass is only used for the back and sides of the tube. It can't be used for the faceplate because x-rays make it turn brown. Instead, barium-strontium glass is used for the faceplate. It seems that use of lead is only a cost optimization, and the whole thing could use barium-strontium glass instead.

Searching for "lead glass CRT browning" on Google found this sample chapter from an unidentified book, provided by the The Society of Photo-Optical Instrumentation Engineers, which includes some details:

https://spie.org/samples/TT54.pdf

The chapter is from:

Kenneth Compton, "Image Performance in CRT Displays", SPIE Tutorial Texts in Optical Engineering Vol. TT54

It's kinda mad we used to stare at an X-Ray gun though :) especially the ones in the 80s didn't quite filter all of them out.

It may just be me, but this video actually seems detailed enough to replicate the process if you have the right materials/machinery.

> https://youtu.be/32yYfTVIzBE

Great video. I’ve got to 6:06 so far no mention of nasty chemicals yet.

Transcript: https://youtubetranscript.com/?v=32yYfTVIzBE

From the transcript (I dislike watching videos), it appears the video never discusses the chemicals involved - but I’m sure some of them are rather toxic. It is an old film, and when it was produced people didn’t see the toxicity of chemicals used in manufacturing processes as being as worthy as note as people do today - both environmental and workplace health/safety issues were less on people’s radar. Plus it obviously is marketing/PR for the manufacturer, and who wants to mention toxic chemicals in something like that?

It's worth mentioning though that in general as our technology has gotten more exotic, so too the chemicals needed to manufacture it have gotten more toxic.

Is there some underlying rule/"law" of fabricated products shrinking in scale requiring increasing energy density/control for their manufacture (more reactive chemistries) presumably to counter a general backdrop of entropy / entropy-density?

10:37 has hydrochloric acid

Sounds like hydrofluoric acid to me, which is even more dangerous. But seeing as you're making a vacuum chamber anyway, perhaps oxygen plasma could be substituted.

https://en.wikipedia.org/wiki/Plasma_cleaning

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