plastic embedding

I have been working with JB4 plastic resin embedding and I'm having problems with the hardness of my blocks.  After being out of the desiccator for 10 minutes or so my blocks soften and I can't get a consistent section.

I'm working with various types of animal tissue usually 2mm x 2mm x2mm.  My procedures involves running through a series of graded ethanol's (70-85-95-100) and straight into JB4 (100mL A solution/1.25g catalyst) for 4 hours.  Then a solution change, rotate overnight, repeat again, and embed after the third change.  Embedding using 25mL catalyzed solution/1.5mL hardener.  Once embedded the molds go into a desiccator under vacuum pressure overnight.

Does anyone have any suggestions or ideas to help me out?  I really need a nice hard, consistent, block.

Thank you very much.
Rachael Emerson
Ward's Microscope Slide Lab

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