Author Topic: Little bit of liquid inside the envelope of a filament LED  (Read 154 times)
Multisubject
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Little bit of liquid inside the envelope of a filament LED « on: April 12, 2026, 03:12:52 PM » Author: Multisubject
I have one filament LED bulb in my house in particular that I have a question about. It is mounted horizontally, and visible in the lowest part of the envelope is what appears to be a drop of some sort of very thick but very clear liquid with very low surface tension. It is a very small amount, I first thought it was just an artifact in the glass, but I have confirmed that this is not the case.

Since the bulb is mounted horizontally, I unscrewed it just about 45 degrees (not enough to be loose, but enough to move the drop away from the lowest spot). The drop did not move, it stayed stuck to the side of the glass where it was before. But when I looked at it the next day, it had re-settled into the new bottom of the lamp. So I re tightened it an just to see the same happen again the next day.

So whatever is in there is a very thick liquid. One of my guesses is that it is some sort of thick silicone oil (or thin silicone grease) that is a byproduct of the silicone phosphor coating on the filaments. And yes this filament bulb is in a hermetically sealed glass envelope, so I highly doubt it is moisture ingression.

Any ideas? Has anyone seen this before? I don't have a picture unfortunately but I can take one next time I am home if I remember.
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RRK
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Re: Little bit of liquid inside the envelope of a filament LED « Reply #1 on: April 12, 2026, 04:13:00 PM » Author: RRK
Yes. For lesser lamps this is a messy fog on the internal surface of the bulb. Definitely a product of filaments coating deterioration.
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Multisubject
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Re: Little bit of liquid inside the envelope of a filament LED « Reply #2 on: Today at 08:49:28 AM » Author: Multisubject
@RRK
Good to know, I'll look out for that from now on
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