I purchased a "New, unused" Sylvania 70W HPS bulb which I planned on using in a fixture I acquired from Goodwill. I am new to this hobby but thanks to a previous topic I started, I now know to check the arc tube for blackening and speckling. See pictures of the eBay item I got. I'm just going to get a refund from the seller as the bulb was not pictured in the listing but was described as new.

With respect to actually new bulbs: what level of blackening around the arc tube is normal? Some sources online advise there should be absolutely no blackening at all (growers). However, my understanding is that manufacturers will run the bulbs for 100 or so hours as a quality check, which I figure would cause the arc tube to blacken. Am I correct about that, or would a new bulb that HAS undergone the "break-in" period show no signs of blackening?

I attached three additional photos which is a line-up of: 1) the Sylvania 70W HPS, 2) a 50W Eye Sunlux HPS, 3) a Satco 70W Mogul base HPS.

The Sunlux was also purchased off eBay from a (different) seller who stated the bulbs are new in box. The Satco I bought from an Italian guy who told me "I never used it... if it works, it works"

The fifth photograph, which is a close-up of the three.

Not looking to make a big deal against the Eyelux seller. Just curiosity as there seems to be some variance in the appearance of arc tubes on packaging and in pictures of brand new bulbs online, which adds to my confusion.

For example, the Sylvania box has a totally white arc tube, but Feit Electric's 70W HPS bulb box features a picture of the bulb with a slightly blackened arc tube. Feit Electric 70W HPS (For the $26 they want I thought I'd be slick and get one on eBay... now I'm making this post LOL

You've got it nearly perfect yourself, in the way you arranged them lamps!

• The Sylvania 70W lamp is heavily used and probably near EOL/few hundred hours left.
• The Eye Sunlux 50W lamp has a bit of usage but won't die anytime soon, and I doubt a hundred hours can blacken the arc tube that much; the Italian guy probably lied to you.
• The Satco 70W lamp is, judging by  photo 5 (IMG_2901.JPG), unused/has very few hours on it. The only reason I have a sliver of doubt is that as per photo 4 (IMG_2900.JPG) it appears as though there are two mild black rings a little away from the electrodes.

Now of course 250W is not the same as 50W but here's an image I found that seems to be a unused 250W HPS lamp by the same Eye Sunlux that made your 50W. Since it's a bigger arc tube it's more prominent but there seems to be barely any blackening across the electrodes, at best a tiny ring would be formed in 100 hours of testing which seems to be way less than what's in your image.
(I may be mistaken, please correct me if so)

Thanks for your input. It was very instructive, and I understand better now how age impacts the appearance of the black rings that appear in arc tubes. It sounds like as time goes on, the rings get thicker (as the oxidation of sodium and aluminum occurs, if I am correct?) and would probably be extremely thin following a 100 hour factory break-in.

I did end up attempting to use the Sylvania bulb, and it cycled off after a few minutes of operation. I told the seller on eBay about the situation and they did refund. I think they mistakenly thought it was a new bulb because it was in a new box. Either way, it worked out.

Good that you got a refund, don’t worry about being new to the hobby, you will quite quickly get the hang of checking discharge tubes 👍
As a guide here are two Philips 50 watt SON-T, left one has many thousands hours on it, the right not even 100, but there are other quick pointers too, below the 50s is an EOL 250 watt GE, oddly the tube doesn’t look bad, but the age of it can clearly be seen in the damage to the inside of the outer jacket!  The tube on the 250 won’t run anymore on any type of 250 HPS gear, even though it doesn’t look that bad.

Yes great examples and I'm happy to see you got the refund. Maybe the seller made a genuine mistake, or maybe he tried to scam you but in the end it doesn't matter, at least you can watch out next time.

You got it right , just note that the oxidation that occurs during long-term usage is generally less damaging to the bulb than with a cold strike that attacks the tips of the electrodes with a 2.5kV DC burst, and a power cycle is significantly more damaging to the lamp. Over the sodium eventually attacks the aluminum under extreme heat during operation which also contributes to the destruction of the electrodes.
A hundred hours should barely leave a mark, at best an extremely thin outline and nowhere near as extreme as what you received.

And for the future, here's how each lamp should look:

• HPS
• Brand new: pure white arc tube with minor rings
• Used: dark grey coating near electrodes
• Quartz MH
• Brand new: completely transparent arc tube
• Used: whitening of glass, mild grey around electrodes (I'm not entirely sure about the second part)
• HPMV
• Brand new: completely transparent arc tube
• Used: silver-black coating near electrodes spread further out

Just for reference, here's an image of a heavily used 250W Bajaj SON-T, taken out of a municipal streetlight and near EOL but still works (the effect is a bit less dramatic on camera, appears more grey irl).