Microscope Maintenance

Microscopes are generally quite maintenance-free. Keeping it free of dust is, however, important.

Microscopes generally do not require much maintenance and should deliver many years of reliable performance if kept well. Improper use of the instruments causes the instruments to age much quicker. Only clean the optical surfaces of the microscope if absolutely necessary. I suggest that you periodically check the following:

  • Cleaning the eye pieces of fat: Grease from the eye lashes ban build up on the lens of the eyepiece and this can attract dust. I recommend that you use compressed air to periodically remove the dust. Do not use the compressed air from cans as these contain additives that can build up. If you have to use a solvent to remove the grease, follow the instructions of the manufacturer. Generally a cotton-swab dipped in some alcohol will remove the grease. Use a rotating motion to remove the grease and be careful that the alcohol does not run into cracks.
  • Cleaning the objectives from immersion oil: Use synthetic immersion oil only! Natural oils may solidify over time. Even if synthetic oils are used, make sure that excess oil is removed after usage. Also check the non-immersion objectives for the presence of immersion oil! It can happen that the non-oil objectives are also rotated into the immersion oil, which might damage them.
  • Checking the working of the gears and cleaning the gears from hardened oil: Over the years the focus knobs might become difficult to turn as the lubrication oil starts to solidify. It is not good to turn the knobs by force. This may increase the wear of the gears over time. The focus system of a microscope is difficult to take apart (and the mechanical stage yet more, due to the ball-bearing). I suggest that you find a company that is able to service the microscope for you.
  • Replacing old light bulbs: Old Halogen bulbs start to shift towards the red end of the spectrum. A blue filter (daylight filter) restores a more balanced color, it is best to replace old bulbs even if they are still functional. When replacing bulbs, do not touch the new bulb with your fingers, as the fat of your fingers will burn on the bulb and decrease the light intensity.

Be careful when using cleaning fluids to clean optical surfaces. Only use those fluids that do not remove the optical coating of the glass surfaces. Use cotton swabs, which have a large surface area to collect dust. Use lens paper to carefully remove excess immersion oil. Do not rub to strongly to prevent scratching. Do not apply the cleaning fluid (eg alcohol) directly to the objective or ocular, apply it to the lens paper first. This way you prevent it from flowing into cracks where they can not be removed easily.

What are some things that have to be maintained?

  • Objectives: The objectives should only be cleaned when necessary. Particular attention should be given to the oil immersion lens. Residual oil on the lens will accumulate dust. The other objectives are essentially maintenance-free.
  • Eyepieces: They will build up oil from the eyelashes and dust. Carefully clean them when needed using the correct cleaning solvent recommended by the manufacturer.
  • Filters: They need to be cleaned from dust every few months, depending on how dusty your environment is.
  • Body: This one will also build up dust, which can be removed using a moist cloth, without cleaning fluids.
  • Mechanical parts: Every couple of years the microscope may require re-lubrication of the focus system and mechanical stage. This is best done by a microscope service company, unless you know yourself what you are doing.
  • Lamps: Halogen and tungsten lamps will also need to be replaced occasionally, even if they are still working, as they change their color temperature with age.

What fluids should I use to clean objective and eyepieces?

Stick to the recommendation of the manufacturer! Do not use solvents used for cleaning windows, do not use liquids for cleaning eyeglasses. These contain additives which might damage the coating of the optical surfaces of the objective and eyepieces. A highly volatile alcohol to ether mixture (70:30) has been recommended in combination with cotton swabs (but check your manufacturer). Only use lens paper for the removal of excess immersion oil from the 100x oil objective, use cotton and the recommended cleaning fluid for the eyepieces. When using lens paper, do not apply pressure, as dust grains might scratch the surface. Cotton swabs have a large surface area to pick up dirt and dust.

Objectives should not be cleaned excessively, and only when necessary. The cleaning solvents do not only remove fats and oils, but might also soften the lens kit holding the front lens in place. The parts should therefore only be exposed to the solvent as short as possible and the solvent should be volatile and evaporate quickly.

It is best to avoid any problematic situations right from the beginning. During my beginning years of microscopy, I made a permanent mount using Eukitt mounting medium. I was too impatient to wait for the medium to dry. I accidentally rotated my 40x objective right into the liquid mounting medium. I had quite some problems removing the medium from the front lens.

Also take care that the cleaning solvent is compatible with the plastic parts of the microscope, in case you accidentally spill something. In short, follow the directions of the manufacturer.

How can I keep the microscope free of dust?

Dust is a problem and often difficult to avoid. Dust is quite disturbing when doing darkfield microscopy, as even the smallest specks form bright spots on the image. Dust on the eyepiece can be easily blown or brushed away, dust on the optical parts inside the microscope are much more difficult to remove. You can minimize dust accumulation by:

  • Using a dust cover
  • Keeping the room reasonably free of dust
  • Mimimizing air currents. These carry dust particles into the room, which then settle down.
  • Using pressurized air from a can: be careful here, often there are additives which accumulate on the optical surfaces and the rapidly expanding air causes a local cooling of the lens elements. I do not know if the rapid cooling and warming of the lenses has a negative effect, but would be careful. Only use pure air and from a safe distance.

How often should the microscope be sent in for maintenance?

Occasionally it might be necessary to send in the microscope for maintenance. In many cases this is not necessary for many years. After several years of operation the mechanical parts of the microscope become difficult to move. It is then time to re-lubricate the microscope. Fungal growth (microscopes used in the tropics) on inner optical parts might also be difficult to be removed by non-experienced people.

  • Send the microscope for maintenance, when the focus knobs or the mechanical stage become difficult to move.
  • Send it for maintenance, when parts of the microscope have to be cleaned, such as difficult to reach optics.
  • Exchange of lamps and objectives does not require a service department.

How often should I clean the optics of the microscope?

For cleaning the eyepieces, use cotton swabs and not lens paper. For removing immersion oil, you can use lens paper. Do not press too hard when cleaning the surfaces, dust or sand grains may scratch the surface. Immersion oil should be removed with lens paper after every use, but it is not necessary to dry-wipe the objective. Make sure that you use synthetic immersion oil, which does not solidify over the years. Immersion oil collects dust and this is the real problem. Always use a dust cover (or put the microscope into a box). The dust can be removed from the body of the device with a moist, but not wet, towel. Do not use solvents or household cleaning fluids on the microscope. And always follow the instructions of the manufacturer.

2 thoughts on “Microscope Maintenance”

  1. I find IPA a good spirit to use, this usually comes with denat, if bought from an optometrist.

    Of course, if your microscope has an anti reflective coating, then using spirits other than those recommeded by your maker is definately a bad idea.

    I use a classical monocular compound luck horseshoe type scope. Critics of this style, argue that they were always more difficult to use, as the movement of the stem drives the optics nearer your face. Some see this as a hazzard.

    In truth, this is not true, it is always necessary to wear safety glasses, before looking at your occular.

    There are many newer more recent, and far more complex microscopes, that REALLY are positively lethal. The biggest problem people tend to ignore, is the lamp. Often the lamp is integral to the scope, and often the lamp is mains powered.

    I recommend use of a microscope with a reflective mirror. An external lamp, is always a more versatile accessory than one affixed to the base, and much safer, as there is no longer a need for the microscope you put near your head, to have any part to do with mains power.

    If you like, you can take Mr fitt’s point and use a rubber lens hood, or make one out of a piece of suitable tube, but contact abrasion against the skin, occurs with prolonged use, especially if you neglect the use of safety glasses. These two minor points will greatly increase your experience, and ensure your personal safety.

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