i'm often asked for advice on caring for ecoprint cloth. my response is generally "treat it as you would treat your hair" because after all wool and silk are quite similar proteins to hair [wool particularly, being keratin] that ought not to be dried in the sun if it can be avoided.*
just as a day at the beach can turn your hair into straw, allowing wet silk to dry in Australian sunshine can make it quite brittle.
and sunshine fades things. black cotton Tshirts as much as ecoprint cloth.
for quite a while, Ecostore woolwash was my potion of choice but recently i indulged and purchased a bottle of Aesop A.P.C. specifically created for washing fine fabrics by hand. it contains petitgrain, lemon and cedarwood among other ingredients and smells like a redwood forest.
i love redwoods.
although it's not inexpensive, the potion is solidly thick [ie you're not paying for water] and a little goes a very long way. i washed my landskin felt travel blanket in it today and BOY did it need washing. one of the drawbacks of felt is that it likes to make friends with all sorts of stuff, consequently three lots of rinsing water were needed to restore it to a more presentable state.
but back to those instructions. use a very small quantity of washing liquid, lukewarm water and le tthe item soak for a bit [i generally have a cup of tea at this point]
then gently squeeze the item in the washbath to help release the grunge. use the spin cycle of the washing machine to extract all the dirty water and then rinse in lukewarm clean water. hang [or lay flat] in the shade to dry.
* yes, before there's a flood of mail to remind me, i know sheep live in the great outdoors and get rained on and dry in the sun :>)