While the etch of lamps usually printed from outside the lamp like the etch of most other products, the american lamps uses an unusual type of etching technology, that in theory is impossible to done: Inside etch, which, as the name suggests, involves printing the etch from INSIDE the lamp, while retaining it visible after making the finish of the lamp, and/or coating the glass with phosphors in case of fluorescent lamps.
How it is possible to do this?

Why should the finish/phosphor make it invisible?

                        inside the lamp

phosphor phosphor phosphor phosphor phosphor
phosphor phosphor ETCH phosphor phosphor
glass glass glass glass glass glass glass glass
                                    ^
                            your eyes

The only question is how the stamp printing the etch looks like.

I understood how the finish/phosphor, don't hides the inside printing. But how it is possible to print from inside the lamp rather than from outside?

I understood how the finish/phosphor, don't hides the inside printing. But how it is possible to print from inside the lamp rather than from outside?

They print it before they apply the phosphor.

But when the bulb/tube is already in its shape, which makes it hard to reach in?

But when the bulb/tube is already in its shape, which makes it hard to reach in?

I imagine a sort of print head with a joint. It enters the lamp envelope through its neck, bends or protrudes there and stamps the etch.
After that it straightens back and gets out of there.

Applying a perfectly even and thin phosphor layer to a shaped lamp looks like a much more difficult task to me.

Initially the "wanna be" lamp is just a straight glass tube. So if the stamp head is just a bit smaller than the tube diameter, just stick it inside from the end and make the print.
Only after that is the tubecoated with the phosphor and the end shaping formed.

The problem is, the machinery for that is way more complex, with more complex movements, so has way slower throughput, leading to significantly  higher manufacturing cost. And the latest was the main motivator, why it was used just by one or two companies and even these gave up after not that long time...

Your answer here:

https://www.youtube.com/watch?v=K08t5lnLPYQ

I think it's stupid that this process is not in use anymore.

I think it's stupid that this process is not in use anymore.

It may appear so, but only when you put away the manufacturing economy. But no maker can ever do that, so there is a dilemma:

(an example, when 4 makers were making the same lamps, but at one time this "inside etch" option come)

1'st maker:
Compare to a standard lamp, ask for higher price for using that. No other difference on the lamp at all (the same life, wear degradation, efficacy, color,...), only the etch being inside and the lamp would have to by be some 10's % more expensive.

2'nd maker:
Other option is to strip down the quality of the rest, to make the room for the "inside etch" process. So the lamp would have inferior life or performance, but will use the inside etch.

3'rd maker:
He sees the market allows the higher price if the lamp would be somewhat superior - so spend it to improve the life and reliability.

4'th maker will keeps the the design original - so no change in life, nor performance, but no extra cost.


Which product would you buy?
Do you think it is worth sacrificing the extra 10's cost for just having the etch durable? Or it is better to spend the extra money on something that may keep the lamp performing better, only the etch wearing sooner?

In lamps etched at the top (as in the extended top of BT lamps or GLS), the stamp is doing straight linear movement. Sure it have to travel longer length from below, but the speed of moving the stamp in and out (over most of it's travel distance, when it is not in contact with anything) is not linked to any other process, so what prevents from moving the stamp in/out very fast ? An air piston doing that at top speed costs peanuts

Consider also, that if there is internal etch then less durable paint can be used, b/c there is nothing to rub it off, so there may be even some savings

In lamps etched at the top (as in the extended top of BT lamps or GLS), the stamp is doing straight linear movement. Sure it have to travel longer length from below, but the speed of moving the stamp in and out (over most of it's travel distance, when it is not in contact with anything) is not linked to any other process, so what prevents from moving the stamp in/out very fast ? An air piston doing that at top speed costs peanuts

It should accurately slow down just before an impact, so the imprint is made correctly. And all that without splashing any paint. That means the acceleration and deceleration are limited. For longer travel the "air gun" wont make it...
Plus recent days an inkjet based digital printing became quite a mainstream (easy pattern storage and pattern replacements - on the data server; easy incorporation of the production tracking like date codes,...), mainly because it needs the bulb moving around the printing head. And that means, the bulb does not have to stop and start again. But the inkjet technology means the target surface should be closer than about a centimeter or so...

Consider also, that if there is internal etch then less durable paint can be used, b/c there is nothing to rub it off, so there may be even some savings

But the inside etch paint should not release any gases (to poison the lamp internal atmosphere). And I would guess, that would be way more difficult for the chemists than just a reasonable robust paint.
Moreover except really special applications, the industry does not require for the etch to "survive" any longer than till the time the lamp gets installed. So a simple water soluble paint is good enough...

Really I would like the makers to invest these money in real lamp functionality, the etch does not generate any light...