At first glance, the topics which will be discussed today seem to lack a common thread. But there is, indeed, such a thread. The harsh effects of harsh environments. The twin papers by Paul on polysulfides are a paradigm, how harsh environments can injure or destroy polysulfide aircraft sealants. One paper deals with those effects of the environment which cause failure of polysulfides, particularly depolymerization. The other with producing an environment which will most effectively depolymerize the sealant.