Surprisingly tight marks feet above lights... Theories? - Page 1
Forum section: electronics / general

author: edy
author_rank: Super Contributor
timestamp: September 18, 2018, 01:55:34 am
content: I noticed these marks in the bathroom a while back and perplexed by how they formed and how they are so well defined, given the distance the ceiling is above the lights. See the photos I attached in which I slightly enhanced the contrast to show it better.I imagine this was formed by dust on the lamps that when heated would travel up and deposit on the ceiling. But how could it be so perfect? Would not air movement have blurred or even completely washed out the pattern? It is quite a distance away.... I understand if it was closer, but what are the chances unless some other effect is happening? Or are the particles travelling so fast and in a straight line up that the air flow (likely also straight up) would concentrate everything on the ceiling?Perhaps it is not even dust from the top of the lamps, but brought by convection flow directly from the air to these areas? Anyways, just wanted to know if anyone else has seen this and if you have any theories. Note that our other bathroom with exactly the same fixture does not have these marks, despite identical layout to the ceiling and bulbs.

author: basinstreetdesign
author_rank: Frequent Contributor
timestamp: September 18, 2018, 02:20:14 am
content: You have 2 bathrooms? Do you shower in this one alone? Maybe that has something to do with it. Maybe the air is otherwise undisturbed above the bulbs at that time. I can imagine a plume of hot air going straight up from each bulb and depositing dirt on a damp, sticky ceiling but I may be completely wrong.

author: Gregg
author_rank: Super Contributor
timestamp: September 18, 2018, 03:44:42 am
content: It could be small insects frying on the lamps sending soot aloft. Also if you burn candles in the house, the updrafts form each lamp could send more soot directly above them.

author: MK14
author_rank: Super Contributor
timestamp: September 18, 2018, 04:18:50 am
content: https://www.homeownershub.com/maintenance/light-bulbs-leaving-black-marks-on-ceiling-567430-.htm

author: Brumby
author_rank: Unknown
timestamp: September 18, 2018, 04:29:20 am
content: I think the heat isn't causing the darkness by charring or whatever. The heat will just create a vertical air flow that rises up and hits the ceiling. The darkness is going to be whatever crap is in the air.As long as there is heat from the lamps and dust in the air, I believe it will be unavoidable.

author: edy
author_rank: Super Contributor
timestamp: September 18, 2018, 04:43:34 am
content: Quote from: MK14 on September 18, 2018, 04:18:50 amThanks, interesting thread. I thought I was losing my mind. Seems most agree with the convection theory and air quality (particles) being forced upwards coupled by a lack of air circulation, thereby leading to very tight marks. It could also be humidity perhaps being forced up and causing mold growth to be exacerbated in those spots? One person suggested partlcles may electrostatically be charged by the bulb which carries them deeper into the wall (I don't buy that theory). We don't smoke and no other lights have ceiling marks. However humidity in that bathroom is definitely likely and there is evidence of mold in the grouting of the shower. I wonder if spores are being carried up and depositing on the ceiling and then fed by moist air that is warmed and carried up to those same areas? I will have to see if I can clean them off and if they come back.Regardless, I am just amazed at how precisely shaped and small the marks are yet so far above the lights themselves. If the ceiling is getting humid from hot shower condensation and then it becomes sticky to any particles including mold spores that get carried up, coupled a with lack of ventilation, I can see how it could perhaps be that focused but I am still surprised.

author: MK14
author_rank: Super Contributor
timestamp: September 18, 2018, 04:52:09 am
content: Yes, it does seem to be a very interesting link.All those theories sound plausible. I agree, it's something like the heat from the bulb, makes the air rise and hit the relatively cold ceiling (or wall). Taking tiny dirt particles with it.One way of finding out more, specific information. Would be to rub those marks, with a clean cloth, or something. Then look at it, and see what the material(s), seem to be.I think I've seen marks like that myself. It always seems to mainly be the tungsten, (hot glass) type of bulb.Humidity does seem to go with mould formation as well.I wonder if the air movements (due to the heat), generate any static electricity or something and/or any mains voltage helps charge up the dirt/air and contribute to those pattern.Because some air fresheners, use ions to clean the air. Those ion (plug into the mains) air freshers, also tend to have black marks, near the (ion) electrodes, on the wall or surface near by.