Mrs. Stewart’s Bluing (MSB) is a brand of fabric bluing agent which whitens fabrics with a dye called Prussian blue (ferric hexacyanoferrate). – Wikipedia
Mrs. Stewart’s Bluing was born in the early 1880s. “MSB” owes its existence to a peddler and his mother-in-law, a marginally successful Five and Ten Cent store, and a fireworks explosion. From the beginning, Mrs. Stewart’s journey has been an interesting one!
In the late 1870s, Al Stewart, a traveling salesman for a Chicago wholesale grocer, was a familiar figure in Iowa and southern Minnesota. In his market basket full of samples, he always carried a bottle of Mrs. Stewart’s Bluing, which he made in his home with his family assisting him according to a formula he had acquired. – Mrs. Stewart’s Bluing Website