How to clean an objective

  • Very small amounts of dust/dirt can make images substantially worse
  • It is important to remove the oil after use (Oil traps dirt and actually slowly dissolves the glue in objectives)
  • Be careful cleaning as the process could damage the objectives if done badly - remember they cost $500 to $12 000 each - be gentle and don't use too much of any cleaning liquid
  • Never use kim wipes on an objective (the fibers are very coarse)

If you have used an oil objective you need to remove the oil when you have finished. Use lens paper to remove the oil (try and mop it up rather than spread it out). Don't over do that though as rubbing the objective when it is completely dry might scratch it (even if you are using lens paper).

There are lots of solutions that can be used to clean objectives. It's a good idea to use two types - one for dissolving water-insoluble dirt, and one for dissolving water-soluble dirt. 70% ethanol works well for the first type (100% evaporates too quickly, and many other solvents are toxic and may actually dissolve the cement of the objective). A dilute detergent is good for the water-soluble dirt. We use 0.5x sparkle, a household detergent that doesn't have an ammonia. There are bottles of both around the scopes.

General procedure for cleaning an objective:

  1. Remove oil with lens paper
  2. 70% ethanol on cotton-tipped applicator
  3. Sparkle on cotton tipped applicator
  4. Distilled water (or breathe on the objective), wipe gently with lens paper

It's a good idea to try and clean objective, and optics in general, in a spiral pattern:

Cleaning other things

Eyepieces also get dirt on them. It's easy to clean them with a cotton tipped applicator soaked in 70% ethanol.

Slides: It's a good idea to make sure your slides are very clean also. It is often worth carefully wiping the coverslip with a cotton-tipped applicator soaked in 70% ethanol.

Zeiss have produced a nice guide: The Clean Microscope