Hildegard, Our EM lab has been using Spurr epoxy for the past 20 years.
Please provide your "get rid of spurr" with references. Thanks, Teresa


>------------------------------------------------------------------------
>The Microscopy ListServer -- Sponsor: The Microscopy Society of America
>To  Subscribe/Unsubscribe -- Send Email to ListServer@MSA.Microscopy.Com
>On-Line Help http://www.msa.microscopy.com/MicroscopyListserver/FAQ.html
>-----------------------------------------------------------------------.
>
>
>Hi,
>
>Spurr's is the most highly crosslinked of all embedding media used for
>LM-TEM.  The higher the crosslinkage, the less likely any stain, whether
>for LM or heavy metal for TEM, is to penetrate well enough to be called
>successfull.
>First:  Get rid of Spurr's.  It contains a potent carcinogen, VCD.  Do you
>need this?
>Second:  If you cannot get rid of Spurr's (try real hard), then use the
>softest mixture you can tolerate for cutting.  Polymerize at 60deg C
>overnight, and see if this is adequate.  This will reduce the final
>crosslinkage.
>Third:  Blocks in existence already! Don't stain well?  Try soaking the
>sections prior to staining for extended periods of time in water, then 5
>min in alcohol, in increasing concentrations until you reach 95%.  Then go
>back down to water stepwise.  Try staining.
>Fourth:  Use as alkaline as possible a vehicle for your stain.  pH 12 is
>about right.
>Fifth:  Combine all of the above.  Does not work?  Soak the sections in
>water and gradually bring to 95% alcohol..  Expose to stain dissolved in
>alcohol.  Does not work?  Forget it.  Start over.
>
>If you have very valuable sections and you must stain them for TEM, use
>alcoholic UA for 10min at 60deg C.  Use Reynolds lead citrate at a pH of
>about 9 or 10.  This last trick is truly a last resort, since the lead may
>dump erratically (or stain easily) at this low pH.
>
>If you polymerize a block at a low power for 45 minutes in a microwave,
>you crosslink the resin to such an extent that nothing, nothing, nothing
>you do will stain it.  (Lost my best meat loaf dish this way).  For TEM we
>do not polymerize resins totally, about 10% of the monomers are left
>unreacted with one another.  If you "drive" the crosslinkage, the block
>will be harder, less elastic, and impenetrable for liquids (except if you
>boil it for a year or so in water).  I am not exaggerating.  I got this
>info out of one my very favorite materials science books.
>
>Don't use Spurr's!
>
>
>Bye,
>hildy