[Histonet] formalin pigment and 10% NBF question

[Cecilia A.]

Hi everyone,

As I read and was told, formalin pigment is seen as a dark precipitate
under light microscope. I also read that you can see this via polarizing
microscope as it is birifringent. I'm wondering: does it first need to be
seen under the light microscope, and birifringence is just a confirmation?
Or, can you see its birifringence without needing to see the precipitates
under the light microscope?

With regards to 10% NBF, do you guys pH this fixative if it's commercially
prepared? Is this always reliably neutral?

Thank you for your time!
Cecilia