For some unknown reason, I awakened the other morning with the image of my grandmother using bluing on the whites in her laundry. Not personally remembering anything else about the bluing used in my childhood, I decided to do some research.
Bluing is made from a synthetic dye called Prussian Blue which is made from ferric hexacyanoferrate; it's basically a blue iron powder suspended in water, with an added pH balancer. It is used because white fabrics eventually turn a dingy color as the fabric never really gets thoroughly clean. A touch of blue dye gives the fabric the slightest blue tint, making it appear white to our eyes. Some laundry detergents today contain fluorescing agents for the same purpose.
So why should I be interested in bluing? Well, for starters, chlorine bleach is toxic. Bleach is particularly bad for my septic tank because it kills the bacteria that make the tank digest properly. Besides, I happen to be one of the people with skin allergic to those fluorescing agents added to detergents.
Reading more, I found that bluing has been used by farmers for over a hundred years in stock watering tanks to keep the algae down. Even in a concentrated form, bluing is non-toxic, and farmers over the years have claimed it reduces distemper and other diseases. (The farmers say that flies carrying those diseases won't lay eggs on blue water.)
While the best known US manufacturer of bluing (Mrs. Stewart's Bluing) makes no such claims, they also say that since 1883 when their business began, they have never received a single report of an animal becoming sick or dying from such practices.
In fact, according to the Atomic Energy Agency, an adult male could eat at least 10 grams of Prussian blue per day without any serious harm. I don't plan to eat any, but it's good to know it wouldn't hurt any fish if I ever build a fishpond!
Before the discovery/invention of synthetic Prussian Blue, people often added lumps of indigo mixed with starch to their rinse water. I also found it has been used in pottery glazing to identify which parts have been glazed prior to firing since any glazing doesn't show up on wet clay. In the firing process, the blue is burned away, leaving the glaze just where the potter wanted.
We all have seen little old ladies with Blue Hair... so don't over-do it!!