MicrobeHunter.com Microscopy Forum

Very, very nice addition with the glycerol comparison. This thread will serve as a definitive reference on this topic!

I've always thought of glycerine as more user friendly than oil, but the two of you have made some very good arguments that have caused me to reconsider. Nevertheless, your images shows that it does indeed act as a serviceable substitute for oil if needed.

I thought it would be nice to add some more examples of water immersion vs oil immersion. I tested water, simply because it is even easier to apply then glycerine.
Switched diatoms, to catch more attraction...
This is a fresh water giant Pinularia sp. (tentative ID, might be wrong), length 380um.
Darkfield was obtained with the D position of the phase contrast condenser, using water, OR with the dedicated Ultracondenser, using oil.
Objectives were:

photo (18): neofluar 10X0.30 dry; for this humble NA, very good DF is obtained with the watered condenser.

photo (19): plan-neofluar 25X0.80 multi-immersion (oil, glycerine, water) used here in water immersion; for this higher NA, mediocre DF is obtained with the watered condenser.

photo (20): planapo 40X~0.7 oil immersion used here in oil immersion, with the oiled Ultracondenser. very good DF is obtained. Note: The diatom was longer than the phototube FOV.

photo (21): neofluar 40X0.75 dry, very good DF is obtained with the watered condenser. Note: The diatom was longer than the phototube FOV.

It seems, therefore, that at least for these condensers, NAs of 0.7-0.8 are the ceiling for good DF when the condenser is watered to the slide, instead of oiling to the slide.
Photos are untouched, except for resizing.

Hobbyst46 wrote: ↑

Thu Mar 25, 2021 11:45 am

apochronaut wrote: ↑

Thu Mar 25, 2021 11:26 am

Oil doesn't need to be completely removed if the immersion objective or condenser...

Glycerine, I think would be better remove completely since it is hygroscopic.
Borosilicate glass also has an RI of 1.47. Are there slides made of such glass ? they might be less expensive than quartz. The major advantage of quartz is transparency to UV.

I've been researching the use of glycerine/glycerol as an immersion medium. You can indeed get borosilicate glass coverslips and they are quite cheap. I've only found a couple of places that sell them (in the UK). Not on ebay, so postage costs more than a box of coverslips. Also, they may be <0.17 thickness and I'm not sure quite what effect a slightly thinner cover glass would have. All things microscopical seem to be more available and cheaper in the USA...

Louise

ps re borosilicate glass: I think only borosilicate 3.3 has a refractive index of 1.47. I got some #1 boro 3.3 coverslips recently but not had a chance to try them with glycerine yet.

Louise