What is fermentation in distilling? Nat February 04, 2020 12:41 Updated Follow The process that occurs when yeast uses sugar to make alcohol and carbon dioxide. This is done prior to distilling. See here for the yeast's role. Related articles How long can I keep wash in a sealed airtight container? What is yeast used for in distilling? Why does the wash smell like rotten eggs? What do I do if I forgot to remove the first 50ml? My wash started to ferment but stopped and the SG reading is not down to 990, what do I do?