Anticipated permanence under a range of temperature and relative humidity storage conditions of bound serial publications can be evaluated utilizing a graphical method called the Isoperm concept. By constructing an Isoperm - a line connecting percent relative humidity and temperature points of equal anticipated permanence - we can calculate the lifetime of books or serials under a certain set of environmental conditions. Isoperms also help calculate the effects of temperature and relative humidity on mold growth, flexibility of the paper and binding, and match human comfort zones with optimum storage conditions. Recent studies of relative humidity cycling at the Library of Congress indicated that the rate of deterioration increases under cycling, but decreases under fixed relative humidity conditions, even in the highest percentages of relative humidity. Other tests show that ultraviolet exposure from the lights in Library of Congress stacks presents no significant problem for paper endurance, including both deacidified and non-treated papers. Serials can be treated much the same as books during the diethyl zinc (DEZ) mass deacidification process, if somewhat longer drying and reaction times for bound volumes are taken into account.