[lee sobol]

hmmm went to clean a regular today, every 4 weeks, noticed on one of their windows what looked to be rust spots lol. from pin head to nail head in size, tried to clean scrape them off but not completely, managed to clean 70% at most on each, really confused as to what they are, really looks and feels like rust, definately not tree sap or the like, anyone come across this before ?

[garyo76]

Could be the result of someone using an angle grinder. The sparks hit the glass and burn into it so cannot be removed.

[Alistair@AWC]

Lee,

I don't know this for a fact but Ive always put that down to an angle grinder being used near the window, maybe for cutting block paving when its being laid and red hot shards of metal coming off the blade and etching onto the window then rusting over time.

[lee sobol]

exactly it, looks like they are burned in as you can see on the outer perimeter what looks like minute spiders legs, hmm thanks for that thought, will ask next time i'm there if they been using anything like that

[Alistair@AWC]

Could be the result of someone using an angle grinder. The sparks hit the glass and burn into it so cannot be removed.

As Gary says, I didn't see your post  

[dazmond]

ive come across it loads of times.it is what gaz and lee say!the windows are knackered mate.nowt you can do about it!

[cozy]

Could be the result of someone using an angle grinder. The sparks hit the glass and burn into it so cannot be removed.

Spot on, that's what we get sometimes.

[R W C™]

Baffles me how people use angle grinders near windows, one of my custys has this on there brand new windows due too roofers using grinder near windows, insurance claim coming there way....

[Llaaww]

I do a jewellers who just had a shutter fitted. You guessed it, they used an angle grinder and trashed the window.

Fireworks do it as well.