quite a while ago, I saved the advice of some of you [in a.c.]
to use chemical sponges to clean soot, etc. from walls.

having the need now to clean soot off a wall, I set forth
in quest of the same. several stores, large and small disclaimed
all knowledge of them

a netsearch provided me with a few trade names, e.g. Bane-Clene
Smoke Off for Fire Damage, Wall-Clene(TM), Smoke-Solv

recommendations would be welcome as would leads to retail
suppliers in Real Life (tm)