Dark/black garments with white panels or trims that are cleaned with dark loads are most at risk. Generally garments should be classified according to the lightest colour in them.
Correctly classifying black and white garments is complex and sometimes they will have to be cleaned on their own.
Often whites suffer greying if they are cleaned in a single bath of distilled solvent without filtration – with or without detergent. Even with detergent, cleaning heavily-soiled whites in a single bath without filtration will result in soiling redepositing, particularly with a low liquor ratio.
Greying is cumulative and even with the most effective processes a small but measurable re-deposition is unavoidable. So soiling particles should quickly be removed from the vicinity of the load. Ideally, a wash with a filter is followed by a rinse in distilled solvent. Failing this, use a two-bath circulating dip with a good detergent charge and liquor ratio in the first bath followed by a distilled rinse.