text: Glass has been around since the Egyptian XVIII Dynasty, as the very earliest specimen is a glass bead that has been dated to that time during the reign of Queen Hatshepsut. Glass is very versatile, and there many different types of glass that serve various purposes, such as stained-glass windows, table glassware, and even glass photographic plates. This means that the treatment of these objects depends upon their uses and original purposes. Glass throughout the ages mostly consisted of glass drinking or eating vessels, and then evolved to be part of churches and housing in the form of window glass. According to the Victoria and Albert Museum, most glass is composed of silica (sand), alkali (usually soda or potash), an alkaline earth (lime) and a little waste glass. Other materials, such as lead and barium, could also be added to create a specialized effect in the finished product. Methods of cleaning have evolved from washing with water, to using special chemical cleansers especially made for glass, to even dismantling a large glass object, like a window, to be assessed and cleaned under a microscope in a lab. There was not a need to clean glass thoroughly until glass evolved as part of the 20th-century home, and it suddenly became important to keep glass windows clean and the common cleanser Windex came into the picture in the 1930s. For glass objects that are not window glass, the most common way of cleaning is by water if the glass object is intact and not super fragile. The Victoria and Albert Museum provides guidance about how to go about this way of cleaning. The methods of cleaning may differ if the glass is already damaged, extremely thin or fragile, or very old.