Eschar

...stable intact eschar on the heels should not be removed. Blood flow in the tissue under the eschar is poor and the wound is susceptible to infection. The eschar acts as a natural barrier to infection by keeping the bacteria from entering the wound. If the eschar becomes unstable (wet, draining, loose, boggy, edematous, red) it should be debrided according to the clinic or facility protocol

When the caustic is removed, the eschar should be punctured for the discharge of the matter, and then dressed with warm emollient poultices...

In another minute there was no letter; but, as with every other relationship in my life, an eschar of ashes. The word is rare, but exact.