A starch mill is a mill for making starch. The input is commonly a vegetable such as potato, casava or tapioca. This is pulped, pressed, dried and ground to form a starch powder which is then used as a food ingredient, glue or fabric treatment.
Felix Rehwald (1926), Starch-making and the manufacture of dextrin, starch sugar, syrup and sugar colouring, Scott Greenwood & Son