Technique Glass mosaics are very attractive because of the light that passes through, creating wonderful plays of color and shine. However, they can be easily broken. So, they are used preferably for wall decorations, except in the case of metal-leaf tiles that are resistant to wear from walking. There are tiles made of homogeneous glass, vitreous paste, enamel threads, enameled glass, with metal leaf and opaque tiles. Glass tiles were introduced in the Middle Ages.