If it helps in any way:

_1._ When I came to UWO 30 years ago I followed local custom
(attributable to the late Ted Walker, who retired soon after
my arrival) and got my lab technician to use a mixture of
4 parts parowax (from supermarket) and one part of a commercial
wax and "polymer" mixture intended for histology. It didn't
seem to make any difference whether the special stuff was
Tissuemat or Paraplast. (Old Ted said parowax alone was a bit
too hard, and the posh stuff softened it a bit.) We used this 
for about 12 years and then I changed to using just the special
histology wax at 100% - not because it was any better but 
because it came as little pellets rather than slabs that took
a couple of hours to melt into the mixture. 
  For a small lab like mine the cost of using an expensive wax
is trivial, but big, busy outfits should seriously consider Ted
Walkers approach (which amounts to lowering the softening
temperature of a harder wax) and save a lot of money. Parowax
in the 1970s was a product of Shell (or ? of Esso). The 
name now seems to be generic for slabs of paraffin about 
10cm square and 1 cm thick, sold 3 to a box in supermarkets.

_2._ Russ Allison, a frequent Histonet contributor, has
investigated and compared a huge number of waxes and published
the results in peer-reviewed journals. He has summarized his
findings in Histonet messages, which should be findable at
www.histosearch.com (though that is a poor substitute for
reading the actual papers). Russ's most conspicuous conclusion
was that simple paraffin wax, without any additives, was as
good as any of the commercial or in-house mixtures.
  If you're reading this, Russ, please denounce me if I have
misquoted your work.
                       John.   
-- 
-------------------------
John A. Kiernan
Department of Anatomy and Cell Biology
The University of Western Ontario
London,   Canada   N6A 5C1
   kiernan@uwo.ca
   http://publish.uwo.ca/~jkiernan/
--
"Monson, Frederick C." wrote:
> The paraffin you get in the store is pure [you can use it to make candy!]!
> Embedding paraffin used to be made up.  Here are some old recipes from Gray,
> P, "Microtomists Formulary and Guide", Krieger Publishing.
> 
>         Altman:  60degreeMP:  paraffin 85, tristearin 10, beeswax 5.
>         Beyer:  paraffin 100, rubber 2, beeswax 0.5
>         Gray 1941:  paraffin(MP 58) 70, rubber 5, beeswax 5, spermaceti 5,
> nevillite "5" or clarite " 15 [see nailpolishes for this acrylic polymer]
> NOTE:  this composition melts at about 50 but will cut 5um ribbons at room
> temp up to 85 degrees F.
>         Pohlman:  paraffin 10, bayberry wax 1
>         Modern paraffin embedments are mixtures of paraffin and various
> other components including polyethylene glycols of different MW's (I think!)
> 
> The above have to mixed thoroughly, and you must BELIEVE that there is NO
> other way!