CAN THE ACTIVATION OF COLOR CENTERS BE REVERSED? CAN THE COLORED GLASS BE MADE CLEAR AGAIN?
Yes. Glass, even at room temperature, is a liquid: the interatomic bonds are weak are and constantly breaking and reforming. These bonds are in fact an interaction of (or, sharing of) the valence electrons of adjacent atoms. (In metals this sharing of electrons results in electrical conduction. For example, in a length of copper wire, the individual electrons at one end of the wire will, in theory, eventually migrate to the other end of the wire, due to random motion and without the application of an outside force). The inter-atomic bonding structure within the bulk of a material places physical constraints upon the valence electrons. Therefore, if you activate a color center (by any means) the alteration in the valence shell will be either stable (unchanging with time) or meta-stable (will change gradually with time). The stronger the interatomic structure (or ‘lattice’ in the case of a true crystal which, unlike a glass, is a solid) the more stable the change. The change can however
