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 Post subject: How did they paint tube numbers back in the day?
PostPosted: Feb Mon 26, 2018 3:29 am 
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What kind of paint would have been used? And I'm assuming some kind of stencils.

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 Post subject: Re: How did they paint tube numbers back in the day?
PostPosted: Feb Mon 26, 2018 5:23 am 
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I figured they got rolled against a round stamp that would also roll through paint as the line ran. Not sure though.


The GE ones with the dots and stuff seem to be acid etched and not painted so im not sure how you'd do that at speed. same idea but acid?

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 Post subject: Re: How did they paint tube numbers back in the day?
PostPosted: Feb Mon 26, 2018 5:43 am 
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Try this link.
https://patents.google.com/patent/US2723205

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 Post subject: Re: How did they paint tube numbers back in the day?
PostPosted: Feb Mon 26, 2018 7:56 pm 
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Hi Michael,
I don't know what type of paint or ink was used, or how it was applied.

But one thing we all know: For the most part it was usually very poor. :cry:

When I need to mark the glass bulb of a tube, I use a "Craft Smart" oil-based paint pen from my local Michael's arts/craft store. This is heat-resistant and will not wipe off with normal solvents.

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 Post subject: Re: How did they paint tube numbers back in the day?
PostPosted: Feb Tue 27, 2018 7:47 pm 
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Location: Orlando, FL, USA
GE dots were sand blasted.

Mosty tubes were printed using a "Tube Roller" that ran a curved rubber print head over the tube base as it rolled by.


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 Post subject: Re: How did they paint tube numbers back in the day?
PostPosted: Mar Thu 01, 2018 2:14 pm 
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And one person said on this topic years ago that he thought that the paint on tubes was purposely formulated to be easily removed by cleaning tubes. That, in his opinion was to deter re-sellers from cleaning used tubes and selling them as new. May be true; might not be true.

Some types are almost white and are easily wiped away. However Sylvania, Westinghouse and RCA for example, often used a very dark gray ink/paint for the tube number that seemed to hold up well. But the logo was still that very flimsy paint. Tubes from the 60s held up well. Tubes from the 30s and 40s seemed to have used magic disappearing ink.

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 Post subject: Re: How did they paint tube numbers back in the day?
PostPosted: Mar Sat 03, 2018 6:57 am 
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Don Cavey makes some interesting points in his post above.

I do a lot of work for customers on vintage tubed audio gear. Quite a bit of what I receive for service contains at least some original tubes, many branded in white paint for the manufacturer of the set. And of course a piece of audio gear containing original branded tubes, if still good, commands a premium price among collectors.* Some of these tube logos are very distinctive in terms of their artwork, Fisher and Pilot in particular. But all these tube markings are very delicate, and can easily be wiped away if one is not careful. As opposed to the tube number itself, which is usually more substantial.


*Note: As an example, show me a Pilot integrated stereo amp from the early 1960's built in the Pilot factory in Long Island, New York City with all original Piilot-branded tubes, including its original Pilot-branded EL84 output tubes and 5AR4 rectifier tube all made by Mullard but branded by them for Pilot, and I will show you an amp which is worth a whole lot of money. 8) Wipe the delicate white Pilot branding off of these Mullard-built tubes, and the value of the amp goes down dramatically.

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 Post subject: Re: How did they paint tube numbers back in the day?
PostPosted: Mar Sat 03, 2018 3:19 pm 
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Poston Drake wrote:
...
*Note: As an example, show me a Pilot integrated stereo amp from the early 1960's built in the Pilot factory in Long Island, New York City with all original Piilot-branded tubes, including its original Pilot-branded EL84 output tubes and 5AR4 rectifier tube all made by Mullard but branded by them for Pilot, and I will show you an amp which is worth a whole lot of money. 8) Wipe the delicate white Pilot branding off of these Mullard-built tubes, and the value of the amp goes down dramatically.

Exactly. It is a shame but true. I guess that flimsy white/yellow/green/red or orange paint (depending on manufacturer) imparts some magical tones to audio tubes, or at least "Some" people think so...

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