Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Self-cleaning glass is a specific type of glass with a surface which keeps itself free of dirt and grime.The field of self-cleaning coatings on glass is divided into two categories: hydrophobic and hydrophilic. These two types of coating both clean themselves through the action of water, the former by rolling droplets and the latter by sheeting water that carries away dirt. Hydrophilic coatings based on titania, however, have an additional property: they can chemically break down adsorbed dirt in sunlight.