A strew slide of ‘Diatoma vulgare’. Prepared by Dingley P Fuge. Mounted in Euparal (Fired and Stained). Olympus BHB microscope using 450nm LED light. 63x Leitz Pl Apo NA 1.40 objective, oil immersion. Olympus Aplanat Achromat condenser, oil immersion, oblique lighting. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. 9 images stacked in Zerene (Pmax).
The images (especially the image with the 63x objective) were low contrast. Euparal (also seen spelt as Euperal) is a low RI mountant, with an RI of 1.48. Compare this with the RI of diatoms (quoted as approx 1.43) and Canada Balsam (1.55). As such Euparal is expected to provide a low contrast image of diatoms, and indeed it was. I’ll be honest I am not sure why someone would use a mountant like this for diatoms, which might explain why not many of these slides are seen.