I just learned about this recently. I have been studying dyeing fabric for some time. One thing that I learned is that rit dye has a new additive called Rit dye fixative. I'm not sure how long they have had it ... I just found out about it. Using this will extend the color of your fabric from fading.

http://www.ritdye.com/Fabric+Treatments.28.51.7.68.lasso?-session=thisSession:4C04D9EE192602CFACLSmi1E0C6E

Like more acid base dyes that use ritayne as an additive that helps your dyed fabric to keep its vibrant color.
I also saw where some use plain salt per rit dye directions.....where others add distilled vinegar to the dye
( not sure about that yet).

Any dye tips!

Billy D.