Author Topic: Blue jelly substance on wires isolation in fixture  (Read 2098 times)
Ash
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Blue jelly substance on wires isolation in fixture « on: October 01, 2011, 12:05:30 PM » Author: Ash
I disassemble some Fitzgerald Lightpacks to clean

The wires inside, at the ends where they are stripped (and WAY over-stripped at that) are covered with some kind of blue-black jelly that makes mess and hard to clean off

What is this substance ?
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Medved
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Re: Blue jelly substance on wires isolation in fixture « Reply #1 on: October 01, 2011, 12:29:51 PM » Author: Medved
Decomposed rubber?
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Ash
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Re: Blue jelly substance on wires isolation in fixture « Reply #2 on: October 01, 2011, 02:06:00 PM » Author: Ash
The wires are PVC not rubber

It appears only on the ends where the isolation is stripped (a lot of it, so that the terminals / sockets / etc that toughed it are painted with it too), but does not appear if i cut off the end of the wire and strip it new
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sol
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Re: Blue jelly substance on wires isolation in fixture « Reply #3 on: October 01, 2011, 06:15:23 PM » Author: sol
Could it be some kind of "conductivity enhancing paste" ? I just made up that term ; it is a wild guess. I am guessing that this paste is in the connectors (terminal block or other).

Other possibility : someone using some kind of paste glue to make (improper) connections, and using some kind of acoustic sealant instead. Acoustic sealant is non-hardening to absorb sound waves in walls. To the unknowing person, it can look like silicone caulking and is applied in the same fashion. Usually acoustic sealant is black.
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SeanB~1
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Re: Blue jelly substance on wires isolation in fixture « Reply #4 on: October 02, 2011, 02:39:23 AM » Author: SeanB~1
If the fixture is around 30 - 40 years old and the wiring is PVC then it is most likely plasticiser from the wire, reacting with the copper in the wire after exposure to the air. The plasiciser in this old wire was a form of PCB, and over long term it tends to separate out of the wire where it is exposed to heat for a long time. This is somewhat toxic, so should not be allowed to get on your hands, and you must immediately wash your hands thoroughly with cold water and preferably a waterless cleaner if you touch it. Do not use hot water as this will make it migrate through your skin.

If you cut and strip the wire the copper will be black for a short distance where oxygen permeated under the sheath and reacted with the plasticiser.
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Ash
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Re: Blue jelly substance on wires isolation in fixture « Reply #5 on: October 02, 2011, 11:16:38 AM » Author: Ash
The fixture is made in 1990

It is either from the wire, or been applied to the wire when stripping. The wires are over-stripped (over 10mm exposed wire out of the connections in many places) and the stuff is mostly on where the wire isolation ends
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SeanB~1
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Re: Blue jelly substance on wires isolation in fixture « Reply #6 on: October 03, 2011, 02:12:05 PM » Author: SeanB~1
It is from the plastic around the wire, and is common on older fixtures, where the wring was made with a more flexible PVC sheathing. Not all batches of the wire will do this, only some batches, so you will find fixtures with and without. More common on wiring dating from the 60's and 1970's, and this could be in a fixture from the 90's with it being old stock wire being used for a run of fixtures. I agree that some fixtures have a poor stripping and dressing of the wiring, but often the push fit connections are not pushed in all the way during assembly, leaving copper exposed.
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Medved
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Re: Blue jelly substance on wires isolation in fixture « Reply #7 on: October 03, 2011, 02:52:09 PM » Author: Medved
I would see the not fullz pushed in wires as the main reason of the bare copper. The wire stripping is done by length preset tools, what are quite immune towards accidentally stripping too long section (you more likely strip only too short section by these)
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Ash
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Re: Blue jelly substance on wires isolation in fixture « Reply #8 on: October 03, 2011, 04:10:38 PM » Author: Ash
There are places with 20mm!! of stripped wire fully outside the connector. No way it was meant to be stripped that long

http://www.lighting-gallery.net/gallery/displayimage.php?pos=-59041
« Last Edit: October 03, 2011, 05:11:10 PM by Ash » Logged
Medved
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Re: Blue jelly substance on wires isolation in fixture « Reply #9 on: October 04, 2011, 01:57:50 AM » Author: Medved
By the way, where it was used?
Wasn't the environment somehow aggressive? (close to the stove in the kitchen exposed to fumes from cooking,...)
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Ash
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Re: Blue jelly substance on wires isolation in fixture « Reply #10 on: October 04, 2011, 02:07:37 AM » Author: Ash
Installed in neutral environment in dry room, nothing aggressive

The exterior of the fixtures is clean (except minor rust from some of the fixtures being submerged in rain water after being discarded, but the jelly is there in all of them including the ones that were not submerged) and has no hint of cooking nearby etc

Also the fixtures are quite enclosed so there is little way for vapors to get in and out in quantities
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