Is there a reason that oil (e.g., vegetable or clear mineral) is not used to make wet mounts in microscopy? I am not referring to oil immersion technique but substituting oil for water in wet mounts in bright field microscopy.

The question is mostly about moss or mold, things that appear plantlike on a slide. The optical properties may be good and the viscosity, as with glycerine, gives a little depth to the slide. Maybe it causes some sort of distortion? I don't see this listed as a suggestion on microscopy sites.


  • $\begingroup$ One thing is that the slide must be viewed quickly, otherwise spores tend to bunch up adhere to other structures. FWIW. $\endgroup$ – daniel Apr 15 '14 at 1:48

Typically wet mounts are used to observe the mobility and behavior of microorganisms. A classical use for a wet mount would be to study something like pond water were you could see all the different organisms swimming around like they would in their natural environment. Oils are more viscus and would impede mobility and might impact behavior or even be toxic to the microorganisms.

If you were an olive oil manufacturer, and you thought you had some odd microbial contamination of your olive oil you might look at a drop of your olive oil between a slide and cover slip thus using an oil based wet mount like you are describing. You might also do this if you were studying the microbiology of an oil spill in water.

There is nothing saying you could not suspend a sample in oil. There may even be a unknown benefit of using this method in certain circumstances, that is waiting to be discovered.

  • $\begingroup$ Have you looked at a mold under the microscope using vegetable or mineral oil? $\endgroup$ – daniel Apr 11 '14 at 15:55
  • $\begingroup$ Can't say that I have. I may not be understanding your question. You mention depth of the slide... If you are trying to view them in more of a 3-D environment then a wet mount might be helpful. Try it with oil and see. $\endgroup$ – Beo Apr 11 '14 at 16:18

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