The sheer curtain on the bedroom window is grotty from the open window. I've bitten the bullet and taken it down and put it through the washing machine.
Now I wait and see whether the dirt is all that was holding it together!
Note: It appears that it isn't, the curtain is washed but still grey, I think it's mouldy, so I will need to soak it in some oxygen bleach to see if that does the trick!
There are ten windows in my house left which need to have their sheer curtains washed. The family room corner window has a sheer which is falling apart on the rail. I don't think I'll wash that one...