After having some trouble with my polarizers everything seems to work OK now
This is acetaminophen (Paracetamol, came with the filters) with Nikon CFN 40/0.70 direct projection on a BHT, stack of 5 images or so
One more same lens
And another one, I think also the CFN 40 but not 100% sure
One more with CFN 40/0.70 this time using a plastic petri dish as a retarder
Images made through a microscope. All subject types.