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Mercury-Starved F15T8

Mercury-Starved F15T8

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I see a flurry of activity about mercury-starved and contaminated lamps, so I went and grabbed an old Feit I've had lying around. I believe this lamp has limited free mercury and not an air leak, though I don't have proof. Here are some characteristics that I've observed which may be attributable to one condition, the other, or both.

1. In both cases, the lamp exhibits reduced output after startup, and slowly attains greater output over a period of minutes. In the long run, the lamp progressively diminishes, both in terms of initial lumens, warmup period, and final lumen output.

2. If the lamp is mercury starved, it will attain maximum output shortly after it reaches it's peak operating temperature, over a period of minutes. On the other hand, if the lamp is contaminated, behavior might be similar, but in severe cases it can continue to brighten over a much longer period, such as several hours after startup. I'll note this isn't a hard and fast rule, but I have observed substantial improvement in contaminated lamps after extended runtime, and this level of improvement due to heavier usage does not seem to be as pronounced in dealing with lack of mercury.

3. Contaminated lamps will suffer starting difficulty long before their output diminishes to a "nightlight" level glow. Mercury starved lamps on the other hand do not have trouble starting until they've depreciated down to almost nothing, and even then they typically fire up on all ballast types without hesitation.

4. The glass of contaminated lamps will become discolored, with brownish deposits at the ends or along the length of the tube. No wear marks besides those from normal operation will appear in a mercury-starved lamp.

5. Contaminated lamps become hot to the touch. Mercury starved lamps won't run much hotter than normal, and may actually use less than their rated power.

6. Contaminated lamps may have visible condensed mercury. Mercury starved lamps will not.

7. Contaminated lamps continue to degrade if put in storage, while the "aging" of mercury starved lamps is suspended while they are off.

I've always been under the impression that most dimmed out lamps in the wild are low on mercury rather than being contaminated by gas fill impurities. Why? Because in my experience, once air poisoning sets in, the lamp simply doesn't last very long. There's a short period where such a lamp can be "revived" by operating them for an extended period, after which it will run up to normal output. If the leak persists, however, it will rapidly regress and within no more than a couple days to weeks the lamp will not strike. The window in which the lamp still starts but won't run up is very small. In contrast, mercury starved lamps can happily continue burning at reduced levels for years until normal cathode EOL.

Perhaps I'm wrong and some of these long-running mercury starved lamps are also affected by impurities. If so, then I have to wonder why these lamps continue to light at a low level of output for so much more time. The rate of impurities entering the lamp cannot be the full explanation. I have one lamp with a very slow leak. While it did take a long time to fail altogether, like all other lamps with air poisoning, it never stabilized at a low level of output like mercury-staved lamp.

feit-mercury-starved-renewed.jpg t17.jpg feit-mercury-starved.jpg vs-ballast-installed.jpg

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Album name:Patrick / Fluorescent
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Date added:Jul 29, 2019
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Jul 29, 2019 at 08:52 PM Author: dor123
Andrew, Globe Collector, wants to see a high resolution spectrum of such lamp (The ones that glowing dim color), to prove that these lamps aren't mercury starved but contaminated.

But Andrew: Mercury can react with the glass, phosphor and electrodes materials.

I"m don't speak English well, and rely on online translating to write in this site.
Please forgive me if my choice of my words looks like offensive, while that isn't my intention.

I only working with the European date format (

I lives in Israel, which is a 230-240V, 50hz country.

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Jul 29, 2019 at 09:02 PM Author: Patrick
Here is a video I posted some time ago. I hypothesize the lamp on the left has an air leak, while the lamp on the right (this same lamp), has too little free mercury. See how the lamp on the left is hardly able to get going, despite being brighter.

Here's another view of the contaminated lamp, where you can see it has a dirty appearance. Is this cathode material? The pattern is a bit different than normal sputtering or evaporation. Here it is again on an electronic ballast. This may have been the last time I lit it. By then it wouldn't strike on preheat.

Another lamp I lost early to a leak was this blue F8T5. Again it had all the signs of contamination. Contrast that to the lamp in this picture, which while very dim, has remained stable over the years.

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Jul 31, 2019 at 06:57 PM Author: don93s
I agree, there are distinct differences between contamination and low mercury. However, the gray area is usually with initial contamination in the production process and it reacts (oxidizes) with the mercury thus effectively reducing the available mercury if the lamp is still able to operate; such as with a very high open voltage or HF ballast. I've had lamps without any mercury operate 'normally' for years (the series companion lamp still lights normally). If such lamps had a leak, they would not be able to do this for such a long period.

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Aug 01, 2019 at 04:04 AM Author: Proteus
It is always a pity if lamps turn out to be contaminated. I've a Philips TLD 58W/25 which seems to have an air leak, the electrode glow in preheat mode looks more incancescent and less gas discharge like, but the filaments are not burning out like in completely leaked tubes.

As well, I've a 15W T12 green lamp which has a little crack - A pity it is air poisoned as well...
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