PVC windows......black on bottom!!HELP

[MrsSanta]

When I have been dusting the ledge have noticed black (sludge) at the join from the window onto the ledge....I have vertical blinds but they dont sit onto top of te window, few inchs gap.

Help any advice, can it be sealed.
The windows are about 11 years old (everest).

TIA

Is it a mix of dust and condensation? If so then I had that and could only clean with an old toothbrush

gosh, dust quite a bit ( well not every day) should that clear it up if I get scrubbibg with a toothbrush.

Well it did for what I had on my windows - but we may be talking about a different sort of black sludge. I did not dust enough though, so if you are dusting regularly and thoroughly then that may not be the root cause.

You can but try though??

thanks rubles will give it a go.