What is the difference between semi-bleached and fully-bleached sponges?
Semi-bleached sponges are cleaned in one acid bath and then a neutralizing soda that lightens the sponge from medium brown to light brown. Fully-bleached sponges receive a second, different, acid bath and neutralization that lightens the sponge even more while cleaning the sponge to a higher degree. Semi-bleaching is used for sponges that are sold into the paint, hardware, cleaning supplies trade, while fully-bleaching is used for sponges sold into the bath and cosmetic trades.