Powder Laundry Detergent » Kirk's Soap- laundry soap powder emon washing powder powder washing Cleaning powder ,Process the small pieces of soap, washing soda and borax together in a food processor or blender until it is well mixed. Avoid breathing in the dust produced from mixing. 3 Store your laundry detergent powder in an airtight container. 4 Use 1-2 tablespoon of homemade laundry detergent per load of laundry.