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Color Restoration Following Formaldehyde Fixation

One of the advantages of simple formalin mixtures is that they permit the natural color to be restored to specimens. This is very useful in medical museum technology, the procedure being fixation in Kiaserling I fluid for some time, followed by the treatment detailed below and final sealing of the specimen in a container of Kaiserling II fluid.

It must be emphasized that this can be done only once, and placing the tissue back into fixative makes it impossible to restore the color a second time. For that reason, tissues to be mounted as museum specimens should not be treated with this technique unless they are ready to be sealed in a container of the final preservative.

  • Ensure that the tissue mass is thoroughly fixed.
  • If tissue blocks are taken, do so from behind the area to be photographed unless the intent is to show from where blocks were made.
  • Place the tissue into a large container in which it can freely move, and deep enough to completely cover it.
  • Add sufficient 80% ethanol to completely cover the specimen. Place paper towels over the specimen if necessary to ensure the ethanol keeps the specimen wetted. No part of the specimen should be in contact with the air.
  • Leave until the colour is restored. Usually this is a minimum of 20 minutes, but visual observation is necessary. Do not leave it too long as the colour will begin to change again if left in the ethanol longer than required.
  • Remove the specimen from the ethanol and gently pat with paper towels to remove the excess ethanol.
  • Photograph the specimen without delay as the natural restored color will slowly deteriorate.
  • Ensure that all photographs required are taken as this procedure will not be able to be repeated.
  • If using lights, turn them off while adjusting the specimen to reduce drying by the heat from the bulbs.
  • If it is necessary to wet the specimen, pat it with plain saline, but do not suspend the specimen in it.
  • Mount the specimen in a museum container, or replace the specimen in formalin when finished.