We coat all of our paraffin blocks after sectioning them because it keeps
the tissue in good form in case we have to recut them a few years from now.
We used to keep the blocks for 30 years or so but recently lost our storage
facility so now only keep them for the time required by law.
We coat them by running them over out hot embedding center until the
surface is coated.  Keeps the little bug critters from eating out the
tissue also.  You see our storage facility used to be in a big building out
on a farm, and some of our blocks were eaten out by roaches.  I wouldn't
think the formalin taste would be too good but they must have liked it.
Now that they are stored in the lab we don't have that problem anymore
Karen in Omaha.