Does anyone know how to get rid of a persistent callus?
I had some success removing calluses by using baking soda. I had calluses due to walking on coral sand/gravel(I lived in the tropics for several years).
How to: Put some(1-2 tsp) baking soda inside each of a pair of finely-woven socks(something like poly/nylon, not cotton/crew), shake the socks so the baking soda is evenly spread across the sock foot-pads, and wear them while you sleep. Use fresh socks/baking soda each night. After about a few days to a week of this any hard/callused skin on your feet will start to peel off, kinda like how dead skin peels off after a sunburn. I only had small/thin calluses, so yours might take longer.
Pros: No more calluses!
Cons: Baking soda made my feet sweat a lot while I was using it, until maybe a few days afterwards. After my calluses were gone, my feet were more sensitive, I couldn't just traipse around in the sand/gravel willy-nilly. I hate wearing socks while sleeping.
Good luck!