[Bungle]

Just the one side needs cleaning. I had a go at it today and failed miserably. I sprayed it with Virosol and it didn't touch it. It doesn't matter if chemicals are used as the drain off is to the ground.

[Splash and dash]

Just the one side needs cleaning. I had a go at it today and failed miserably. I sprayed it with Virosol and it didn't touch it. It doesn't matter if chemicals are used as the drain off is to the ground.

Hypo mix , smaller brush so you can apply more pressure and hot water

[Smudger]

Any idea what it is ?

are there a lot trees around it ?

Hypo would be my next go to - unless its like a tree sap or you might want to use a large non scratch pad on a holder - bit like bronze wool

[Small but perfectley formed]

Hypo scrub rinse then Hypo again scrub rinse .
Try thick bleach boosted with hypo this may cling to glass for longer contact

[Bungle]

I don't use hypo but did think of spraying it with a bleach solution and leave it a couple of days and scrub it off.

[Slacky]

I tend to find hypo needs rinsing before it dries. It’ll leave really stubborn salts on the glass if you don’t.