Sentence:  Argiento had been trained so rigorously by the Jesuits that Michelangelo was unable to change his habits : up before dawn to scrub the floors , whether they were dirty or not ; water boiling on the <WSD>fire</WSD> for washing laundry every day , the pots scoured with river sand after each meal . 
Meaning of the word marked with <WSD> tags:  the process of combustion of inflammable materials producing heat and light and (often) smoke