[Histonet] de-waxing / staining station question

[Monfils, Paul]

Dewaxing in one change of solvent, regardless of time in the solvent, is not a good idea. After a rack of slides has passed through the first xylene, that dish no longer contains xylene.  It contains a solution of paraffin in xylene, and with each additional rack, that paraffin solution becomes more concentrated.  Therefore you will not be going from xylene into absolute alcohol, but from a paraffin solution into absolute alcohol.  Since the paraffin in that solution is not soluble in alcohol, it will precipitate on the slides and in the tissue.  The purpose of having additional alcohols is not that one xylene can't dissolve all the paraffin out of the tissue.  It is to get rid of the dissolved paraffin so that you are not carrying paraffin into the first alcohol.