methacrylate blocks
 

Hi,
I have been producing plastic blocks for histology for many years with no problems at all. Suddenly my sections are not staining and I wondered if anyone had experienced any similar problems. The blocks polymerise and section perfectly, but when I stain them with Lees methylene blue basic fuchsin, all the plastic stains dark purple and the specimen doesn't stain at all. It is not the stain, as I have used stored unstained sections and these stain correctly. I have replaced every chemical in the process, including all the ethanol dilutions but no improvement. I have also used different samples and even slides. I was using 2 hydroxy ethyl methacrylate from Merck and have just bought some from Sigma to try instead. Very near to tearing my hair out! Any suggestions gratefully received.
Christine