A process for formation of a base, which comprises reacting an acetylide compound with a salt. The acetylide compound has the following formula:(R--C.tbd.C--).sub.n Mwherein R is a monovalent group selected from the group consisting of an alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aralkyl group, an aryl group and a heterocyclic group, each of which may have one or more substituent groups; M is an n-valent transition metal atom; and n is 1, 2 or 3. The salt is composed of an anion having an affinity for the transition metal (M) (the affinity of the anion for the transition metal is more than that of the acetylide anion (R--C.tbd.C.crclbar.)), and a cation derived from one selected from the group consisting of an alkali metal, an alkaline earth metal, ammonia and an organic base. A light-sensitive material containing the acetylide compound and the salt is also disclosed.