My mother-in-law gave me a cotton black and white skirt. It was basically clean but had a few yellow areas so I searched out a dry cleaner that was green making a much longer drive than needed as I hate the smell of formaldehyde and other cleaners.
When I dropped it off I specifically said I was bringing it in for the yellowing on some of the white areas and she marked the spots.
When I picked it up the yellow was still there. I was told that they cannot get those spots out, that it was from either hanging in a closet for a long period of time or perhaps from hanging in the closet in a plastic bag.
Had i known that I would have saved myself 1 hour and $10 as it did not need cleaning.