In January, 2011, Mary O'Dwyer brought us her grandfather's 1875 christening gown, to see if we could do anything to help her. We could not believe our eyes when she arrived with a pair of lovely cotton garments the color of robin's eggs. The blue was streaky and could not mask a pattern of brown stains, most noticeable on the front.
If you are one of the housewives who use powdered or lump blue, then be sure to take great care to add a small amount of water to the powdered blue before use and to tie ball, or lump blue, in a small cloth bag, which may be dipped and squeezed in the water before using. Otherwise the bluing is likely to be unevenly distributed and cause spots to form on the clothes. In spite of these precautions, there will be this tendency unless a very few clothes are put in at one time and these kept in motion.
If you use the liquid Prussian blue, remember that it contains salts of iron that turn to iron-rust in the presence of the alkali from soap, particularly when heat is applied, as in ironing, for example. Consequently, to avoid iron-rust stains on the material, take every care to have the clothes thoroughly rinsed so that all traces of soap are removed before bluing.
Although we still have no first-hand experience treating blued textiles, we're delighted at the success of this old-school recipe.