That depends on the type of bag you have. Our Seventies bags are made from faux leather or from a combination of linen/cotton and faux leather. You don't have to spray faux leather as it is already water-repellent. Any visible dirt can be easily removed with lukewarm water and a soft cloth. If you wish, you can spray the linen/cotton part of the bag with water repellent and dirt protection spray. Our Caretta bags are already provided with water and dirt-repellent coating. So, you do not have to use the spray on them.