4.11.
EPON EMBEDDING
111
Luft found that when he cured Epon mixtures that were formulated as
he handled Araldite 502, the blocks were rather too soft. It proved easy
to obtain much harder blocks by substituting a different "hardener."
Actually, the hardness can be controlled at will over a wide range by
using different blends of two mixtures. This allows a flexibility in the
handling of this resin that often proves useful. The two resin mixtures
are made up as follows:
Mixture A
Epon 812 62 ml
DDSA (dodecenyl succinic anyhydride) 100 ml
Mixture B
Epon 812 100 ml
MNA (Methyl nadic anhydride) 89 ml
(National Aniline Div., Allied Chemical and Dye Corp., New
York)
These Epon mixtures are stable, and can be kept for many months in
a refrigerator. They ordinarily are blended, and accelerator added, just
before use. The softest blocks that one is apt to use might be made from
2 parts of A to 1 part of B. A decidedly hard block should result from
reversing these proportions. In our own laboratory, we routinely use a
1:1 mixture if embedding reasonably soft tissue without too much collagen in it, or 3:7 if decidedly harder blocks are desired. The accelerator
used is DMP-30, added to the selected resin mixture in the proportion of
1.5 to 2.0%. This must be stirred in very thoroughly. Originally, Luft
proposed increasing the incubation temperature in three steps, from
35°-60°C over a 36 hour period. This is unnecessary for 60°C can be used
from the start. Two nights and a day of heat polymerization seem desirable, and apparently there is some further slow curing even at room
temperature during the days and weeks that follow, so that sectioning
properties often seem to improve simply with prolonged standing.
In our own laboratory we have found the above procedure for using
Epon to be quite reproducible and entirely satisfactory, providing
we
have had good Epon. We did get off to a bad start with this resin, for
the lot we first obtained never worked properly. It perhaps was wet. This
may have been our fault since at the time we did not realize that Epon
is somewhat hydroscopic. Therefore, not only must stock solutions be
kept carefully covered when not in use, but also containers used during
infiltration procedures should be stoppered except when transfers have
EPON EMBEDDING
111
Luft found that when he cured Epon mixtures that were formulated as
he handled Araldite 502, the blocks were rather too soft. It proved easy
to obtain much harder blocks by substituting a different "hardener."
Actually, the hardness can be controlled at will over a wide range by
using different blends of two mixtures. This allows a flexibility in the
handling of this resin that often proves useful. The two resin mixtures
are made up as follows:
Mixture A
Epon 812 62 ml
DDSA (dodecenyl succinic anyhydride) 100 ml
Mixture B
Epon 812 100 ml
MNA (Methyl nadic anhydride) 89 ml
(National Aniline Div., Allied Chemical and Dye Corp., New
York)
These Epon mixtures are stable, and can be kept for many months in
a refrigerator. They ordinarily are blended, and accelerator added, just
before use. The softest blocks that one is apt to use might be made from
2 parts of A to 1 part of B. A decidedly hard block should result from
reversing these proportions. In our own laboratory, we routinely use a
1:1 mixture if embedding reasonably soft tissue without too much collagen in it, or 3:7 if decidedly harder blocks are desired. The accelerator
used is DMP-30, added to the selected resin mixture in the proportion of
1.5 to 2.0%. This must be stirred in very thoroughly. Originally, Luft
proposed increasing the incubation temperature in three steps, from
35°-60°C over a 36 hour period. This is unnecessary for 60°C can be used
from the start. Two nights and a day of heat polymerization seem desirable, and apparently there is some further slow curing even at room
temperature during the days and weeks that follow, so that sectioning
properties often seem to improve simply with prolonged standing.
In our own laboratory we have found the above procedure for using
Epon to be quite reproducible and entirely satisfactory, providing
we
have had good Epon. We did get off to a bad start with this resin, for
the lot we first obtained never worked properly. It perhaps was wet. This
may have been our fault since at the time we did not realize that Epon
is somewhat hydroscopic. Therefore, not only must stock solutions be
kept carefully covered when not in use, but also containers used during
infiltration procedures should be stoppered except when transfers have