Coffee grounds saved up after use and stored in the freezer until we had lots.
Ratio of dyestuff to wool
The first time we didn’t measure it so it was lots....
For the iron modified batch, 1.3 K wet coffee grounds to 92 g carded wool
Coffee grounds boiled up for an hour or so an left to stew overnight. Strained through kitchen towel, then wool added and heated to just below simmer for an hour and left over night.
Paler muddier shades from exhaust
Second picture shows soft green given with iron modifier.
Not yet tested.