We've all done it. Let the patina on a carbon steel knife get a bit too patina-y. Clue: if it's rough and raised and orange, that ain't a patina. Or left a stainless knife wet or with something acidic on it for far too long. Another clue here, it's stain-LESS. Our advice has always been to go for a rust eraser to remove the rust and knock back the patina or to try some Barkeepers' Friend. 

Barkeeper's Friend is a mild abrasive powder which does the job a treat but the powder's a bit of a fiddle to direct and it's not necessarily something that's under every kitchen sink. This is where the tik-tok-famous Pink Stuff comes in. Beloved of clean-fluencers everywhere, cheap as chips, and much more ubiquitous. And turns out it does exactly the same thing while also being non-toxic and vegan. Pictures below. We are converts.