fog at the inside of front lens

[yellow]

... no clue where to post this, so I use "general" ...


With a few of my lights, I have the "problem", that on firing them up (+ some mins of running), fog appears at the inside of the lens,
starting in the middle and spreading out, making a circle.
It not really worsens beam or output, as it mostly "only" covers the very inside and thus the spill part of the light, but it just annoys me ...


I must have opened the light(s) quite a number of times, wiped everything with towel,
a few times even using hot air to get whatever moisture away ...
... does not help in any way.

Anyone had similar problems + a good solution?

(the lights are watertight and often submerged - for cooling when doing battery runtime tests)

 

[richardhill5]

I have had a similar issue in the past. I determined it was the oil on the tread, and upon heating up caused the fog. Once I removed most of the oil from the tread, it no longer happened to my light. I don't take the head off and on so I don't see a need for the lubrication.