I've recently bought a microscope and been looking at a lot of bacteria and such, and have quickly run out of clean slides. I've seen videos and articles saying how you shouldn't clean microscope slides with a paper towel and to use an ultrasonic cleaner instead. I don't have access to an ultrasonic cleaner, so I am wondering what is wrong with cleaning them with a paper towel?

Also if anyone knows of any good liquid solutions for cleaning slides that information would much be appreciated.


The main reason to avoid paper towels, tissues, and etc. is that they shed lint (paper fibers) which will be left behind on your slide and eventually interfere with your prep. They look small to the naked eye, but they are not small compared to the prep on your slide.

The other issue with paper towels and etc. is that there might be some particulate matter in the paper that's hard enough to scratch glass or optical coatings. This is more of an issue for optics - especially coated ones - than for cheap microscope slides, but it's something to consider.

If you're not mounting permanent preps then ultrasonic cleaning is probably a bit of overkill - although I have a surplus sonicator and it does a great job on a lot of tasks. It's generally sufficient to rinse the slide with distilled or deionized water and then follow up with (clean) alcohol. Optical purists will say spectroscopy grade methanol, but for home use any reasonably pure MeOH, EtOH or iPrOH will probably do. The main concern, again, is leaving behind particulates or residues. You can allow the slides to air dry if you're using pure alcohol, or use a piece of lens tissue (lint free paper tissue) to help them dry faster. I've also used Kimwipes in a pinch, but they're not truly lint free so not ideal. They're still much better than a tissue or paper towel.

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    $\begingroup$ +1. Distilled water, a wipe with Kimwipes if needed, then EtOH is all I use in the lab. Keep your slides in the box they came with, don't expose them. $\endgroup$ – vkehayas May 4 '18 at 10:34
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    $\begingroup$ For reference, a 280-pack of 1-ply kimwipes on fishersci.com is 9 dollars plus shipping. Other purists will still say buy lens wipes, which are like 1200 for $95 on fisher, but I find kimwipes do the job. $\endgroup$ – CKM May 4 '18 at 13:07
  • $\begingroup$ Kimwipes do this job quite well, but generic lens paper is quite cheap too - I think I got ~400 sheets on amazon for ~$10 and it's decent quality. Doesn't matter for this kind of cleaning, but for actual optics (if you're even wiping) it can be very hepful. $\endgroup$ – bjarchi May 4 '18 at 21:16
  • $\begingroup$ Methanol is toxic and very volatile, so you shouldn't advise its use without also advising to use it under a chemical hood. $\endgroup$ – Guillaume May 9 '18 at 19:45

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