Problems associated with poor embedding in epoxy resins:
Blocks are difficult to section
Sections may disintegrate upon contact with water or the electron beam
Holes in the sections
Unevenly cured blocks
Blocks are either too soft or too hard
Factors that cause poor embedding in epoxy resins:
The presence of water in absolute dehydration solvents and in the ingredients of the embedding mixture
Solutions to the causes:
Use either fresh or well capped bottles of dehydration solvents.
Embedding should be carried out at relative humidities below 50%. Dellman, H.D. and Pearson, C.B. (1977).“Better epoxy resin embedding for electron microscopy at a low relative humidity”. Stain Technol., 52:5
Since epoxy resin is hygroscopic, extreme care should be taken to prevent contamination by water.
Accurate measurement of accelerators.
Complete mixing without incurring air into the mixture (Use a "PTFE" or glass rod for at least 20 minutes).