 Glass can also be welded to metals and ceramics , although with metals the process is usually more adhesion to the surface of the metal rather than a commingling of the two materials . However , certain glasses will typically bond only to certain metals . For example , lead glass bonds readily to copper or molybdenum , but not to aluminum . Tungsten electrodes are often used in lighting but will not bond to quartz glass , so the tungsten is often wetted with molten borosilicate glass , which bonds to both tungsten and quartz . However , care must be taken to ensure that all materials have similar coefficients of thermal expansion to prevent cracking both when the object cools and when it is heated again . Special alloys are often used for this purpose , ensuring that the coefficients of expansion match , and sometimes thin , metallic coatings may be applied to a metal to create a good bond with the glass . 
