Method of preparing holograms and the holograms prepared thereby

A method of preparing a hologram which uses gelatin as the binder which method comprises holographically exposing the holographic material by use of coherent light, developing the holographic image by a chemical or physical process and before processing, simultaneously or subsequently, treating the material with an aqueous solution of a polymer which comprises a tertiary amino group in the repeating unit, said polymer being formed by reacting methylene bisacrylamide or a substituted derivative thereof with a compound which comprises two secondary amino groups, or which polymer comprises a tertiary amino in a side claim and which comprises repeating units of the formula ##STR4## where R.sub.1 is hydrogen or a methyl group, R.sub.2 and R.sub.3 are each methyl or ethyl and n is 2-4 or R.sub.2 and R.sub.3 represent the atoms necessary to complete a saturated heterocyclic ring.