Better epoxy resin embedding for electron microscopy at low relative humidity.

In the absence of other factors known to influence sectioning properties, high environmental relative humidity is shown to yield poorly embedded tissue. Humidity-related effects are avoided if the following embedding precedure is used; impregnate tissues using the following solutions 1) 70% alcohol - 5 minutes, 2) 95% alcohol - 2 x 15 minutes, 3) absolute alcohol - 3 x 20 minutes, 4) acetone - 2 x 15 minutes, 5) 1:1 mixture of acetone-epoxy resin (DDSA, 63.4 g; Araldite 502, 5.6 g; Epon 812, 39.4 g; DMP-30, 2.6 g) - 1 hour, 6) acetone-epoxy resin 1:3 - 1 hour, 7) epoxy resin - 1 hour; complete the preparation of blocks as follows 8) when tissues have been oriented in epoxy resin in flat embedding molds, place molds in one evacuated vacuum desiccator 10 cm above a 2 cm layer of Drierite for 24 hours at room temperature, 9) raise temperature to 60 C and maintain for 3 days to cure resin.