A graded ethanol series is the method of choice when embedding in 'L.R. White'. Acetone acts as a radical scavenger in the resin system and therefore traces of acetone left in the tissue at curing can interfere with this polymerization. If the use of 2,2-dimethoxypropane is considered vital we recommend either a protracted resin infiltration or washing the tissue with dry ethanol prior to infiltration in order to minimize the chance of acetone contamination of the final resin. A 1mm cube of animal tissue will be adequately infiltrated in about 3 hours if 4-6 changes of 'L.R. White' at 60 degrees C are employed during this period. An overnight infiltration at room temperature, followed by two short changes of resin will often be more convenient, however.
Larger blocks do require significantly longer infiltration times than small ones.
Osmium tetroxide treated tissues should not be 'cold-cured' with the accelerator. This process is strongly exothermic and the dark color of the tissue leads to a focal heat accumulation which can cause local problems in and around the tissue. If the tissue is not osmium tetroxide post-fixed then curing with 'L.R. White' accelerator may be employed. As with curing blocks for light microscopy we recommend cooling the molds during polymerizing, but there is no need to exclude oxygen from the surface of the curing block. Thermal curing should be used for osmicated specimens and may be used for all specimens.