Why does this happen to mirrors?

[AVANTE 499]

What's with the weird black sludge-like pattern around the mirrors border? Its there on the rear view mirror. Is there a fix for it? Or is replacement the solution?

[Hyaenidae 781]

Did you try wiping it off with a tissue?

[iRage 2,085]

52 minutes ago, □AVANTE□ said:

What's with the weird black sludge-like pattern around the mirrors border? Its there on the rear view mirror. Is there a fix for it? Or is replacement the solution?

In a mirror there is a reflective compound that is sandwiched between the forward glass and the back panel (in home mirrors the reflective material is painted on). In the past it used to be mercury..I do not know if they still use mercury or not.  What happens is sometimes the sealant around the mirror breaks and then moisture gets in between the glass and the reflective compound and this causes the reflective compound to deform like this or get black spots, etc...

This looks like something of the sort....hard to say without actually touching and looking at the mirror.

[AVANTE 499]

14 minutes ago, iRage said:

This looks like something of the sort....hard to say without actually touching and looking at the mirror.

Thanks for that info! Really impressed by the abundance of knowledge around here. Now I can impress a date with my knowledge on rear-view mirrors!

jk, It seems to exist inside the mirror. Can't feel a thing when you touch it. The same material is there on RHS rear-view mirror but a bit whitish too.

 

31 minutes ago, Hyaenidae said:

Did you try wiping it off with a tissue?

It seems to be inside the mirror so that won't do!

Edited October 14, 2019 by □AVANTE□

[iRage 2,085]

18 minutes ago, □AVANTE□ said:

Thanks for that info! Really impressed by the abundance of knowledge around here. Now I can impress a date with my knowledge on rear-view mirrors!

jk, It seems to exist inside the mirror. Can't feel a thing when you touch it. The same material is there on RHS rear-view mirror but a bit whitish too.

 

It seems to be inside the mirror so that won't do!

Okay..so it is the reflective compound getting stained...

[Davy 2,229]

Yep, that's definitely moisture causing the reflective coating to degrade. There's no easy solution to this that I'm aware of. 

Make sure you keep that mirror clean and dry to prevent it from spreading. Avoid cleaning with strong chemicals (which I believe may have caused this in the first place). If you must clean, wipe completely dry with a paper towel after cleaning with glass cleaner. Especially along the bottom edge, where the liquid can collect and make its way behind the mirror. 

[Quiet 234]

Some sort of strong chemical was used to clean the mirror resulting in the liquid dripping to the bottom and degrading the rubber/compound sealing. During subsequent cleaning the liquid has diluted the reflective layer behind the mirror. I don't think it will spread

[iRage 2,085]

1 hour ago, Quiet said:

Some sort of strong chemical was used to clean the mirror resulting in the liquid dripping to the bottom and degrading the rubber/compound sealing. During subsequent cleaning the liquid has diluted the reflective layer behind the mirror. I don't think it will spread

Its a bit hard to say....over time humidity can get in there and then start spotting and degrading it....but it can be a slow process 

[wolseley 28]

AFAIK there is no solution other than replacing, if it is an issue for you. There are enough mirrors available at used parts dealers  for  common jap vehicles.