Hi Erin,

There are some higher melt point paraffins available from several companies and you may wish to explore that first.  Contact various manufacturers like Surgipath, Polysciences, Thermo Shandon and Richard Allan as these companies all have a variety of paraffin formulas that are designed for Histology.  Most will give you some samples to try and see if it will overcome your issue.  It depends on why you want the harder paraffin as to which will perform best for your laboratory.

As several people have said Carbowax is a pain to use and may void warranties on some of your equipment if it is not an approved type of embedding media.  This is always an area that is overlooked and is important if you are paying for repairs due to clogs or other issues rather than having it covered by a service contract or warranty.  Be careful about those little details that your supervisor will not be happy with when the bill comes in even if they requested the change.

Hope this helps,

Pam Marcum
 -------------- Original message ----------------------
From: "Rittman, Barry R" 
> Erin
> I agree totally with Rene.
> Carbowax is a real pain to work with. 
> To harden the wax you have you may want to try adding Ceresin, a higher MP wax.
> If you need a much harden wax than this then the ester waxes are more suitable 
> although they also have their problems.
> A pertinent question here is why specifically does your lab director want or 
> need a higher MP wax, what problems are you having and what tissues are you 
> processing?
> Barry
> 
> -----Original Message-----
> From: histonet-bounces@lists.utsouthwestern.edu 
> [mailto:histonet-bounces@lists.utsouthwestern.edu] On Behalf Of Rene J Buesa
> Sent: Wednesday, January 11, 2006 7:54 AM
> To: Erin Wrona; histonet@lists.utsouthwestern.edu
> Subject: Re: [Histonet] carbowax
> 
> Hi Erin:
>   Many years ago Carbowax was considered "a blessing" because you could 
> infiltrate tissue (after fixation) with it avoiding dehydration and clearing. 
> This sounds great but it was a mess to store and cut because of this same 
> inherent quality of being water soluble (or miscible,as you wish).
>   If you need harder paraffin (to cut hard tissues) you just simply should try 
> to buy high melting point paraffin.
>   When I worked with plant stems I used to infiltrate them with a heigh melting 
> point paraffin (63-65ºC) manufactured on those days by Merck (Darmstadt). I am 
> sure that high melting point paraffins can be found in the market.
>   I thing you should avoid carbowax.
>   Hope this will help.
>   René J.
> 
> Erin Wrona  wrote:
>   Hi all,
> 
> Our lab director wants us to try using carbowax polyethylene glycol as an 
> embedding medium because it has a slightly higher melting point than our 
> paraffin. I have never used it other than in formulations for frozen sections, 
> in which case it is water soluble. One of the other techs here thinks that it is 
> always water soluble. Does anyone know for sure?
> 
> The specifics are: ems product #19770, PEG 8000 flakes, melting point 60-63 
> degrees. 
> 
> Thanks in advance,
> Erin Wrona
> San Francisco, CA
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