How to keep black clothing black??

[mildred37]

I have a couple of pairs of black jeans and a cardigan that I love, but they have faded over time. Any tips or ideas as to how I can either get some colour back into them (not keen on using a dye....) or avoid on clothes in the future? I always do a 30deg. wash and use fairy gel + fabric conditioner.

Watching with interest and hoping someone clever has an answer! I have some black jeans that are still new-only washed about 6 times and they are so faded! I did one of those washing machine dyes on a pair of black trousers a while back and the looked good for a while but faded again after a few washes!

Rinsing with diluted vinegar is supposed to improve black clothing, but don't remember details.