The best way to avoid having to clean the lenses on your microscope is to use it carefully and keep the microscope covered when not in use. If a lens gets dirty or gummed up, here's what you should do.

Only clean your microscope lenses when they are dirty and use the proper materials!

Try to locate the dirt. Is it on the eyepiece lens or objective lens? If you see a spot when looking in the microscope and you see it at all powers it is probably on the outside of the eyepiece lens. If your eyepiece lens turns, turn it and see if the spot moves. If so, the dirt is on the eyepiece lens. If the spot doesn't move when you turn the eyepiece lens and you see it at all powers then the dirt is internal and you should probably have it cleaned by a professional. If you only see it at one power, the dirt is most likely on that particular objective lens.

Sometimes all you need to do is blow off the residue. Use a squeeze bulb or one of the camera lens cleaner bulbs with the camel hair brush on the end. If you need more air pressure, you can use the compressed air cans that are used to clean dust out of keyboards. Do not use any sprays with cleaners. Once blown clean, lightly wipe the lens with Kimwipes. These are lint-free paper tissue made for use with fine machinery and optical parts. They are made by Kimberly-Clarke, (who also makes Kleenex), and are available in art supply and larger paper supply stores among other places. The proper motion to use when working with these tissues is to "swipe" the lens in one direction rather than rub in a circular motion. Do not clean lenses with ordinary cloth, paper towel, or fingers!

Another good cleaning tissue is Tiffen Lens Tissue (available at photo stores) In lieu of a brush, you can use the paper. Roll the tissue into a tube and tear it in half, with the feathery torn ends together. Use it as a one-time brush. Use several for very dirty lenses. A regular lens brush can hold grit and cause scratching. If the grime is still there, you will need to use a solvent.

When using solvents, put a drop or two on the paper then hold it against the lens for a few seconds to dissolve the crud. Then lightly wipe it free. Distilled water is the first solvent to try. If that doesn't work, try alcohol. Isopropyl alcohol is one of the best solvents but it must be at least 90%+ pure (do not use rubbing alcohol, 30% water. Use the full strength variety). Everclear which is grain alcohol (you must be 21!) can also be used but it doesn't do as well in dissolving crud (although it does mix with orange juice quite well!). If you have something like Balsam stuck on the lens, you must resort to a stronger solvent like Acetone or Xylene.

Acetone should never be put on plastic parts as it dissolves most paints and plastics. ZEISS makes a lens cleaning solution (spray) and Edmund Scientific carries one called Lens Luster Cleaning Fluid. Some people swear by a solution called ROR, although I've never tried it. You can find it here. When adding the solvent, put only a small amount on the kimwipe and always apply it from the underside going upward to the lens. This will keep the liquid from running down into the lens. Do not remove the lenses from the instrument unless absolutely necessary and never soak even the tip of an objective lens in a container of solvent! It could dissolve the cement used to hold the glass lenses in place.

Microscope World carries a complete cleaning kit that includes a soft lens brush, microfiber cleaning cloth, lens paper, lens cleaning solution and an air blower. I prefer using an air blower over the compressed air cans, as it is more gentle on lenses.

Sometimes objective lenses get gunked up with glycerine, blood or other albuminous material. It can be removed with lens paper dipped in a weak ammonia solution (one dropper full of household ammonia in 1/2 cup water).

If you are using a 100x objective with immersion oil, just simply "swipe" the excess oil off the lens with a kimwipe after use. Occasionally dust may build up on the lightly oiled surface so if you wish to completely remove the oil then you must use an oil soluble solvent. For the Cargille Type A or B immersion oil, you can use Naptha, Xylene, or turpentine (use very small amounts on the kimwipe). Do not use water, alcohol or acetone as the oil is insoluble to these solvents. Consult the MSDS info that is supplied with your immersion oil to see what solvents are recommended. To remove other oily substances, we recommend using the detergent called Persil and prepare a solution of 1 part Persil to 100 parts water.

Periodically inspect the power cords and plugs for safety and have a replacement bulb available. Professional cleaning and adjusting should be performed whenever necessary at an optical shop specializing in microscopes. Unless you are a professional do not attempt to clean or adjust the inner optics of your microscope.

When your microscope is not in use, it should be placed in a case or covered with a dust cover and stored in a safe area where it won't get knocked over or stolen. If you have a heavy duty vinyl dust cover, double cover your microscope with it and a plastic shopping bag. When the dust builds up on the shopping bag, replace it.