So everybody and their brother has a trick to keep your whites whiter, and we all know, some of the work and some of them don't. There's bleach, which works, but doesn't smell that great (unless you're my mom) and an assortment of whitener/brightners that work to varying degrees. The Rit one pretty well, but it can be hard to find sometimes.
But what about your blacks? How do you keep your blacks blacker?
Ooh! I know!
More Rit Dye! This is all you need:
1 pack Black Rit Dye
1/2 your usual amount of detergent
1 cup of white vinegar
a pile of faded black clothes.
Add your laundry and detergent the way you always do. Then add the whole pack of dye and the cup of vinegar to the washtub. Run through on a regular wash cycle, plus an extra rinse to get the excess dye out of your clothes and any residue out of your washing machine.
If any dye residue still remains in the washing machine, run a load with bleach, but no actual laundry, but I've only had this happen once, and it was when our old washer was acting up.
This can also be used for adding blue back into fading jeans or for re-dying and changing the color of items. Changing a color altogether may take twice through with dye, but it depends on how dramatic a change you're going for.
Enjoy!