White clothing can naturally turn yellow during washing. Bluing is a liquid added into laundry water to prevent the yellowing. Before chemicals were made in factories, laundresses over the years whitened clothes with blue from indigo or from powdered blue smalt, which is ground glass with a cobalt ingredient. The indigo was processed and formed into stone blue, fig blue or thumb blue. Bluing has been used since the 18th century and is still used today.
Boil water in a pot. Add the grated soap to the boiling water and stir until soap is melted.
Pour the soapy water into the clean pail and add the Borax substitute, shampoo, and washing soda. Stir until all ingredients are dissolved.
Add a little of the pigment. Stir. Continue adding the pigment until you reach a "sky blue."
Pour in 7.57 litres (2 gallons) of water. Stir.
Add 118 ml (1/2 cup) of the mixture to the rinse water. Put the lid on after use. Stir after each use.
The bluing mixture will gel after use and will need to be stirred. Prussian Blue pigment can be purchased at art, writing or craft supply stores or online.