From @tenbobbit I received two Postumus coins that were severely affected by verdigris. Knowing that lye seems to be a miracle solution, I tossed the coins into a haphazardly-mixed lye solution for about 6 hours and the results were magical. Billon/silver washed Pax reverse: Billon/silver washed Oriens reverse: As you can see, the lye treatment all but eliminated all traces of tche verdigris, for the most part. There is still a little left on the body of Oriens and the face of Postumus on the Pax coin, but overall, I think this is a 100% improvement. PROS: removes 95-99% of verdigris from surface can reveal previously-hidden silvering seems to brighten up silvering significantly CONS: softens out some details (see the NS in ORIENS, and the sharpness of the POSTVMVS legends) Overall, I think this is a great result. DISCLAIMER: only subject to coins that are either a) inexpensive or b) guinea pigs as you can, and will, ruin some coins with lye. Do not soak any of your 4-figure coins in lye, no matter what.