I have been doing a bit of mushroom microscopy in recent months, and this generally requires the use a 100x magnification oil immersion lens (the spores and related bits have sizes in the order of single micro meters, so 1000x overall magnification is needed to see them well enough and measure them). And getting most of the oil immersion lens requires keeping it clean, which I imagine is taught somewhere in the Microscopy 101 course, so nobody really talks about, and it took me a while to find a way that works reliably well. So in case this saves some other budding microscopist time …

Before I get to the cleaning itself, make sure you are using a decent quality oil. Some of the cheaper oils tend to harden rather quickly, and if you don’t clean them fast enough, it becomes quite hard to get them off later, you will need to remove the lens for that, and it’s a total PITA (Microscience is probably the best place in the UK for reagents for mushroom microscopy, and they also sell decent non-hardening oil).

For the cleaning you will need a suitable lens cleaner (I can recommend ROR, which in the UK can be purchased from Brunnel Microscopes), two lint-free lens cleaning tissues (I use PEC PADs), and a good quality, untreated, microfibre cloth. Before you start mark the two tissues as no. 1 and no. 2, so you can tell them apart. The process itself is simple:

  1. Wipe the bulk of the oil from the lease with the no. 1 tissue,
  2. Put a drop of the lens cleaning fluid on a clean place on tissue no. 2 and wipe the lens,
  3. Repeat step 2 once more,
  4. Use a clean part of the microfibre cloth to wipe the lens dry,
  5. Repeat step 4 once more.

Every time you do this, you move a bit along the tissues and cloth to a clean part, it’s not that hard to keep track of this. Eventually tissue no. 1 gets discarded, tissue no. 2 then becomes tissue no. 1, and the microfibre cloth gets washed.

That’s it, works really well every time, without having to take lens out and inspect it.

[The cover image are the spores of bloody brittlegill viewed under a phase-contrast lens; for the russulas you generally get a better look at the spores under a normal lens, but I rather like the colour scheme on this one.]