Effects of processing at 45 C on staining

Tissue processed at a constant temperature of 45 C including the use of paraffin wax with a melting point of 45 C displays staining characteristics that are sometimes reversed from those associated with the more usual processing schedules and wax with a melting point of 58-60 C. Staining with acid dyes, particularly in trichrome methods, are most susceptible to these changes. We suggest that this is directly related to dye molecular size and to differences in the tissue structure resulting from the heat to which the tissues were exposed.