Never Go Back to 40x After Oil.
A quick reference for keeping immersion oil off the dry 40x objective.
On most microscopes the 40x sits right next to the 100x oil objective. Swing back from 100x to 40x and the 40x drags straight through the oil drop. The 40x is a dry lens, so oil on its front lens makes every image hazy. Wiped off right away, it's no big deal. Once it dries, it takes special solvents and care to remove.
Do this
- Lower the stage first. A few turns down before you touch the nosepiece.
- Turn away from the 40x. Rotate toward 4x or 10x so the 40x never passes over the oil.
- Need 40x again? Clean the slide. Wipe the oil off the slide first, or use a fresh slide.
- Wet oil on the 40x? Blot it now. Lens paper, light touch, right away, before it dries.
- Wipe the 100x when you're done. Lens paper after every session, every time.
Avoid this
- Swinging back through the drop. The quickest way to put oil on a dry lens.
- Letting it sit. Dried oil needs special solvents and care. That's a service call.
- Scrubbing or using solvents yourself. Rubbing drags oil and grit across the coating.
- Oil on any lens not marked Oil. Only oil objectives take oil. The 40x is a dry lens.
- More than one drop. Extra oil spreads to the nosepiece and the lenses next to it. See Immersion Oil: One Drop.
The habit, every time
Done at 100x
Lower the stage
Turn away from the 40x
Wet oil on the 40x? Blot now
Not sure if your 40x already has oil on it? If images at 40x look soft or foggy no matter how you focus, and 10x looks fine, dried oil is a likely cause. Work through Hazy Image? Check This First.
Try it in 3D or VR
See what oil does to a 40x lens on a 3D microscope, and practice the safe way to go from 40x to 100x. Open the oil immersion lab on a phone or computer, or in the Meta Quest browser for VR.
Watch it in a minute
40x hazy and the oil has dried? We'll take it from there.
Need hands-on help? See our veterinary microscope service in Houston.
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