Bleaching clays used for the purification of edible oils are bentonites treated with acids where the crystal structure of the smectite clay minerals is partially attacked in order to increase porosity and surface properties. Hydrophobisation of bentonites can be achieved by exchange of organic molecules in the smectite interlayer. Those organoclays are able to swell in nonpolar solvents and are frequently used as rheological additive in paints and waxes.