The tissue is stained with a regressive haematoxylin, consisting of Ferric Chloride and Iodine. The differentiating is accomplished by using excess mordant (Ferric Chloride) to break the tissue mordant dye complex. The dye will be attracted to the larger amount of mordant in the differentiating solution and will be removed from the tissue. The elastic tissue has the strongest affinity for the iron-haematoxylin complex and will retain the dye longer than the other tissue elements.