A sponge, when first purchased, is frequently hard, stiff, and gritty. To soften it, and dislodge the particles of sea-sand from its crevices, (having first soaked and squeezed it through several cold waters,) put the sponge into a clean tin sauce-pan, set it over the fire, and boil it a quarter of an hour. Then take it out, put it into a bowl of cold water, and squeeze it well, Wash out the sauce-pan, and return the sponge to it, filling up with clean cold water, and boil it another quarter of an hour. Repeat the process, giving it three boils in fresh water; or more than three if you find it still gritty. Take care not to boil it too long, or it will become tender, and drop to pieces. You may bleach it by adding to the water a few drops of oil of vitriol.
The Mediterranean sponges are the best.
After using a sponge, always wash it immediately in clean water, squeeze it out, and put it to dry.