How to Clean Immersion Oil Off Your 100x Objective Lens

How to clean immersion oil off an objective lens

This article describes how to clean off immersion oils properly so your expensive components work better and last longer. 

Unlike some optics components, which should only be cleaned when dirty, immersion lenses need to be cleaned after every use, even if additional slides are going to be observed.

It is a small step but a vital one. 

Keeping your optics clean at all times – no oil, other spots or smears – is essential for reliable high quality imaging and good lab practice.  

And if oil is left on the objective lens – even overnight – it can be difficult to remove without damaging the lens. It can also lead to expensive repairs.

For example, if oil seeps between the outer barrel and the spring-mounted inner barrel of the lens and dries, the mechanism becomes sticky. And a lens with a stuck spring mount will have to be returned to the manufacturer to be fixed. Or if oil seeps underneath the top lens? Another case for a repair facility.  

Your expensive component just became more expensive – another good reason for keeping your objective lens clean as a matter of routine.

So here are some hints and tips which explain how to clean off immersion oils before it causes damage. The number one tip we have already discussed.

Clean off the oil immediately after using it

The oil will still be wet and easy to remove. And by following this procedure, you can ensure the microscope system is ready for the next technician to use.

 Use lens paper to clean off the oil

Gently wick away the oil with lens paper – never a tissue, Kimwipe or anything besides lens paper. Lens paper doesn’t scratch.

Microscope Optics Cleaning Kit

Do not put any pressure on the lens

Never press on the lens with your finger or anything else. Wipe the lens paper across the lens a few times, using a clean area of the lens paper each time, until no more oil comes off. If the oil has dripped down the side onto the sloped metal area, you can use your finger to carefully wipe the oil off, avoiding the lens.

Repeat with as many lens papers as required

Using plenty of fresh lens papers is essential to the success of this procedure. Wipe until no oil streaks are seen on the paper and then discard each sheet to avoid inadvertent contamination. Your natural tendency to minimise waste is misdirected, considering the relative cost of lens paper compared to the potential of damaging an expensive objective.

Clean the surfaces of your slides

Once the lens is cleaned, clean immersion oil from both surfaces of your specimen slide using laboratory tissues. All areas on the instrument, such as portions of the base or stand, should be routinely checked for any traces of immersion oil, which if found, may be removed with laboratory towels or soft cotton cloth.

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