Common washing soda or soda-crystals is the decahydrate, Na2C03 IoH 2 O, which appears as large clear monoclinic crystals.
Hence they are best known as " washing-soda."
For the simplest recipe found above, you simply shave one whole bar of soap, and stir it together with a half cup of each the Borax and washing soda.
Pour hot mixture into a large, clean bucket and add the Borax and washing soda.
Add melted soap, washing soda and Borax.