Managing Microscope Oil Mess

Managing Microscope Oil Mess

A common classroom complaint is the inevitable mess students make when using the 100x oil objective on their microscopes. Sure, immersion oil can be messy, but it plays a critical role in microscopy. Using proper technique and following our tips below will help you to minimize the mess.

Why is oil necessary?

At high magnification, oil is used to fill the air gap between the objective lens and the cover glass. With a refractive index similar to glass, oil prevents light from being scattered by the air. This helps the objective to resolve the image.

So what are the typical issues faced when using oil?

• Over application, leaving oil all over the stage, condenser, etc.

• Accidentally getting oil on the 40x objective due to its similar working distance to the 100x

• Spilling oil on the countertop

• Accidently transferring oil from the 100x to other objectives during cleanup (THERE IS NO NEED TO WIPE DOWN ANY OBJECTIVE OTHER THAN THE 100x unless they also already have oil on them)

It is very important to make sure oil is not left on objective lenses. The other objectives are not sealed like the 100x since they are not intended to be used with oil. In the short term, the oil will cause the objective to look blurry or ‘broken’ which leads to a service call for a simple problem. However, oil left on any objective (including the 100x) will eventually seep into the lens over time, rendering it useless. This can be a costly mistake.

How to minimize the mess and prevent expensive problems.

1. Use a bottle with an applicator tip to apply oil, not a glass jar/pipette.

2. Only a small drop of oil is required. Passing the 100x objective through the oil once or twice will help spread the small drop across the entire coverslip.

3. Re-arrange the objective order. This can help avoid a student accidentally dragging the 40x objective into the oil. Swap the 4x with the 40x. Additionally, Accu-Scope offers a long working distance 40x objective to prevent this problem.  

4. After using the 100x objective, remove the slide and completely clean the oil off the coverslip before going back to use others.

5. Wipe the 100x objective completely clean after each use. Do not use this wipe on other objectives as you could spread oil to them.

6. USE KIMWIPE OVER LENS PAPER – Kimwipes absorb oil much better than lens paper, which smears it.

No Oil, No Mess.

There’s no getting around it, to achieve the best 1000x magnification you need to use some sort of immersion liquid… but that immersion liquid does not have to be oil! Accu-Scope makes a 100x water immersion objective for some of their microscopes. Rather than applying a drop of oil to your slide, you apply a drop of water! You can also get a 100x dry objective. While the resolution of the dry objective is not as good as a 100x oil, it may make sense if students are continually getting oil on the other lenses, causing blurry images.

As always, if you have questions about oil immersion objectives just email us at

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