ABSTRACT
The term ‘staining’ is generally used to include all methods of colouring tissue. The simplest distinction between staining and dyeing is that defined by Kiernan and Boon and Drijver: where colouring is caused by linking a dye molecule and tissue substrate, the process is called dyeing; if the tissue is stained by solution contact alone, the process is called staining. The fixative used in the protocol can influence the staining reaction of the tissue. Adding salts to the staining solution increases metachromasia, while polar molecules such as alcohols retard the effect. The area chosen for staining work should be well lit by top lighting, and face preferably onto windows. Staining baths should be laid out near the sink in a manner that allows the work to progress without crossing over baths holding other reagents. Haematoxylin is colourless, and the dyeing action is due to the oxidation product haematein.
