When chemistry has its own way.
I bet i couldn’t replicate this if i tried…..I had used this tannin bath already twice, and it was filtered water, but the tannin had started to oxidize, and it also showed me that either my filtered water system leaves some iron in, or that the original scouring had left a residual, BUT it’s the most gorgeous silver and fawn i’ve ever seen. The right side is actually the bottom edges, and the left is the middle where it was folded over a rod to hang to dry. The iron migrated then to the bottoms so it was still pretty “loose”.
I’m hoping that after a good rinse, it’s much the same. (Silk velvet)