Tube labeling: Paint? Etched?

[mike_mccue]

I've been collecting tubes from a variety of discarded appliances.

Most of them are dirty and I've been reluctant to clean them because the paint is so fragile.

I realized that I have a simple curiosity regarding the labels that seem etched into the glass. I am speaking of the small label like "12AX7" that you can find in addition to any of the painted labeling.

Does anyone know how that labeling was applied? Was it chemically etched? Blasted with abbrassives? etc.

Finally, do you find that the etched labels are "permanent" or are they just less fragile than the paint?

Thanks and best regards,
mike

[redelephant]

Hehe...I've managed to neutralize some rare and expencive NOS tubes such as Mullard and Philips by cleaning the glass with technical alcohol. Real brilliant eh? Now they are just plain no-names, and nothing I can use to impress other geeks like me with;(

The etched lettering appears to hold tho, so wouldnt be too concerned with that.

Now I gently wash dirty tubes with luke warm water.

[J M Fahey]

.I've managed to neutralize some rare and expencive NOS tubes such as Mullard and Philips by cleaning the glass with technical alcohol

.
Please don't hate me, but if you could accomplish such feat, they were "EBay wonders" for sure.
I've been silkscreening for ages, never on glass but my suppliers used to carry "glass inks" (for glass syringes and similar) which AFAIK contained some member of the fluorhidric family as priming component and "ceramics/glass" inks which partially melted in an oven after application (think 500ºC or more) ; either of them could only be removed with agressive surface grinding and polishing, there was *no* chemical way to do it.
In modern times they were commercially supplanted by epoxy inks, which were *relatively* weaker but still resist wiping them with acetone or toluene, let alone technical alcohol.
There's a cottage industry entirely dedicated to rebranding tubes for the "connoisseurs", if you catch my drift.
Oh well !!!

[redelephant]

Hehe...no way man, these were given to me from the old dude working at the college's lab. He had a stash of tubes in a box and he gave me some. (Just a short while before I approached him the colleges tossed the entire supply of NOS tubes in the dumpster, Philips, Mullard, RCA, GE, etc.etc)
He had saved a few, about one wall rack full or about a few hundred, of tubes for reasons he couldn't say, but refused to let me have more than a dozen or so. The guy is now long gone, and the tubes were probably tossed in the trash as soon as he left.

I've bought some 3A5 tubes on ebay, that's it.

Btw. I am no 'connoisseur' ragarding NOS tubes. I do appreciate old hardware, espescially tubes for historical reasons, but really couldn't give a rats a*s about showing them off to other people.

[Steve Conner]

Nope, real old tubes have ink that comes off easily too. I have a similar tube stash as Redelephant, I've intercepted a lot of tube equipment on its way to the scrap heap and pulled all of the tubes out. (Best find: 7 GEC KT88s, "GEC Made In England" stickers and all.)

Very tough glass inks might be available, but the tube makers probably thought that the tubes wouldn't get as much handling as, say, lab glassware. They were supposed to get thrown into a radio and forgotten about until they wore out, not be lovingly fondled and polished by collectors.

A real tube geek (with advanced Tubesperger's Syndrome ) can tell what make the tube is even if the ink is gone.

[J M Fahey]

Maybe those *are* NOS but relabelled.
In the old days it was *very* common (it's well documented) for some "good" manufacturer to have some batches actually made by another "good" manufacturer.
Maybe economy of scale or just trying to offer the full Monty, even if some types didn't justify making 50000 of them, the generally accepted minimum to make any tube.
Nothing shady implied, but commercial savvy.
Of course if, say, Telefunken sent 10000 ECC83 relabelled RCA and 18000 relabelled Miniwatt, said relabelling would not have justified the best, strongest printing.
Of course, considering they were not exactly lab equipment was a certain possibility too.
I have often found , in the same tube, *both* sets of markings: a *very* visible screened one and a much fainter but almost impossible to erase etched one.
I also have some absolutely "naked" ones.
By tube connoisseurs I was referring to nobody around here; we are the practical guys, aren't we?
PS: I LOVED the

Tubesperger's Syndrome

definition, and, fact is, *many* can easily describe a tube's birthplace by the plates length and color, the dimple in the glass button, and 1000 other small details.
So be it.
Good luck

[mike_mccue]

That's why I am asking... I rescued 32 1957 long black plate RCA 12AX7s from an appliance that was headed to the dumpster and that evening I washed off all the labels before I realized how fragile the paint was.

I'm glad they were all etched with 12AX7 U.S.A.

I recognize them as RCA black plates and I have them all in carefully labeled white boxes... but I feel like I ruined their value for any future tube nerds.

As I've said elsewhere, I am not selling tubes... I'm just happy to grab them when I see them and I'd like to take care of them until it's time to pass them on.

best regards,
mike

[J M Fahey]

Well, if you dare and it's important, you can re-label them.
Screening a somewhat narrow (say, less than 1/2 inch) but long strip along the tube axis is simple, silk has flexibility and can print on the slightly curved surface, within reason.
Now, to print like a "belt" around the cylinder, you'll need a special jig which turns the tube while being printed, not justified.
Can you post some picture of the surviving inscriptions?

[Kazooman]

Similar Experience

I had a similar experience when I tried to clean the dust off some old tubes. These were in equipment I have had for over 45 years, so I can date them back at least that far. I wiped them with a wet cloth and was surprised to find that the paint came right off. I don't remember the specific brands, but none of them would have been collector's items. Just cheap radio type stuff.

[dai h.]

I've removed baked on dust with an Exacto knife blade and a pointy instrument (might have been one of those things for electronics work with a hook on the other side and plastic handle sort of portion in the middle) and lint-free cloth carefully working around the (very delible) ink. I don't feel like so much of a tube nerd these days but I suppose it might be worth doing to help ID the tube later on. Another old crappy tubes related thing is, Deoxit seems to work for cleaning pins. Putting them in some kind of container, bag, then wetting the pins a bit and leaving them (sealed, or pretty sealed) seems to help (if you Q-tip the pins later, some black stuff--which I assume is the unwanted dirt, etc.--comes off).

[jrfrond]

It's not letter-perfect, but I label all newly-installed tubes with the installation date using a silver Sharpie. We're getting into the habit of marking all installed parts. These are the handiest friggin' markers ever made! I've used them on pulled tubes to rewrite the tube number.