If this second experiment with coffee-grinds wool dying does not give the results I desire, I'm done with coffee-dying.
I saved up a lot of grinds. This is all espresso or french press grinds, so the 'remains' often came with some dark liquid ready for dying.
Since I was experimenting, I thought I'd grab a variety of yarns to dye, including some small handspun bits in white(ish).
We'll see in a few hours...
The cowl did not get darker. No change at all - which would be evident from different colours in the yarn because I did not immerse the entire item.
I think the problem is the Fisherman's wool. It is the yarn that came out too 'caramel' in colour. The handspun alpaca and wool yielded a nicer, but still subtle colour. At least it's not yellow/caramel.
However, I'm also disappointed that, despite the gross volume of coffee grinds used, the colour is still weak. It's actually WEAKER than last time. Maybe I should have left the grinds in again! A friend dyed her yarn with dye made from fresh grinds (i.e., not used for drinking first, but coffee was out of date or cheap stuff) and her yarn was a much richer brown. I'm not willing to use my good coffee beans for that.