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My outside window sills are looking dirty with spots of lichen which are difficult to remove.  I have bought some spray-on cream which is for uvpc but it does not clean very well.  It does leave a nice shine.   My granddaughter wants to use bleach but I worried it will be harmful to the plastic or turn the white to yellow.   Any advice please?

I gave up with the UPVC cleaners a couple of years ago and started to use bleach, just on the mucky spots (my problem is spider poo) and I've had no problems with yellowing.....just try an inconspicuous bit for a week or two?

OH uses "Silky" which is a caravan/ motorhome cleaner. (occaisionally!!) ;)

Cillit Bang good stuff on offer at the moment in home bargins £1-75 I take it on all jobs with me. After a few years UPVC starts to grain anyway bleach should not harm it ;)

Thanks for replies.
CillitBang from home bargains sounds good and I will try to get some Silky when I find a caravan place.
Bleach for the worse spots.    Thanks again.