By the use of holographic storage techniques, the conductivity of iron doped lithium niobate has been investigated. The results indicate that the conductivity of the material immediately after hologram formation is much greater than previously suspected. This increased conductivity is shown to be a direct result of the multivalent properties of the iron dopant molecules, and the underlying theory necessary to account for the effect is presented, this theory being an elaboration of the bulk photovoltaic theory of von der Linde and Glass.