Picro-mercuric-alcohol was recommended by Lendrum and coworkers for the secondary fixation of sections at 56°C overnight for the demonstration of fibrin in his trichrome staining methods. His recommended method of preparation was extended fixation in formal sublimate (days), following which thin sections were cut and baked onto slides, then dewaxed and treated with trichlorethylene to “degrease” for 1-2 days. The sections could then be refixed in picro-mercuric-alcohol for some time, overnight if possible.

Simply refixing paraffin sections in picro-mercuric-ethanol for an hour or two at 56°C is often satisfactory. Bouin’s fluid at 56°C for an hour or two is also often satisfactory.