To make washing soda, clean a lidded jar, label it, bake baking soda for two hours, and store it in the jar. This 2 1/2-hour process requires an oven, a baking sheet, baking soda, a lidded jar, water, soap, an adhesive label, a marker, oven mitts and a large spoon.Continue Reading
Preheat the oven to 400 degrees Fahrenheit. Wash and dry a lidded jar, write "washing soda" on an adhesive label, and apply it to the jar. Set the jar aside.
Spread several cups of baking soda over a baking sheet. When the oven is ready, insert the baking sheet, and leave it there for one hour. Put on oven mitts, take the baking sheet out of the oven, stir the contents, and return it to the oven. Bake it for another hour, turn off the oven, and remove the baking sheet. The powder should be a very pale yellow color. Set the baking sheet on the stove until it returns to room temperature.
Scoop up the washing soda, pack it into the jar, and screw on the lid. Keep the container tightly sealed to prevent the washing soda from turning back into baking soda.