When washing black shirts and sheets they often come out with white marks any ideas why?

Use a liquid washing detergent. But if you are in a hard water area and have a machine that is a few years old it could be the lime in the water and the build up of lime in the machine. I use calgon to stop the machine liming up.

I had the same problem with my daughters black work pants, I have found by using Woolite for darks, and washing at 30 degrees its fine. Woolite is available from most supermarkets. I had been using washing powder and washing at 40 degrees, it seems the soap powder had not been dissolving properly.

You should also make sure your soap powder drawer is clean too sometimes the powder makes a horrible sticky mess under the drawer and it transfers onto the clothes.

Hope this helps

if ur using washing powder that could be the cause particularly if u r filling the machine full as it doesnt give a chance for the soap to be washed away. i have found that using a washing liquid like persil colour liquid or similar is much better on dark coloured things and avoid s this problem. the other thing u should look at if its not that is the fabric conditioner if that isnot dissolving properly. hope this helps

I have never had this problem since I switched from washing powders to liquids & find Sainsbury's own non-bio liquid to be excellent & consistently reliable.I also wash everything on 40 ,nothing higher than that temperature

Try washing them inside out then any marks are on the inside so wont be seen! Or make sure your not using to much washing powder!

I always wash everything inside out because it stops them fading so fast!

this used to happen to me until I started letting the washer fill with water first, then add your detergent (try not to use too much). After swishing the detergent around to let it dissolve in the water, add your black sheets or t-shirts. I don't have that problem anymore. Hope that helps

Try doing a second rinse and/or using a liquid detergent.