This method is described as far surpassing, in efficiency and beauty of result, any other known process. The soap is brushed off clean with a delicate brush. The hats, while yet wet, are immersed in a bath, prepared of three-fourths of an ounce of sulphite of hydro-sulphite of soda, and four to six pounds of water, and are freely handled and pressed, to promote the soaking in of the lye through the interstices of the plaits. No harm is to be apprehended from this manipulation, as the previous washing has rendered the straw pliable, and without danger of fracture. The hats are then removed from the lye, and three-fourths of an ounce of muriatic acid of commerce being added and well stirred into this lye, the hats are quickly replunged in it. To secure a uniform action of the acid upon the lye which is in the hats, particular care must be taken that the hats be submerged at once, and kept in this situation. In order to prevent the escape of the liberated sulphurous acid gas, the vessel employed is, after the second immersion kept closed, until the operation be completed ; this takee place in about thirty minutes, more or less, according to the darkness of the straws. When sufficiently acted on by the gas, the hats are removed, washed clean in pure water, dried, and finished as usual.
This article was originally published with the title "Improved Method of Bleaching Straw Hats" in Scientific American 13, 12, 94 (November 1857)