The lenses of a biological microscope--including the eyepiece (the lens you look through) and objectives (the lenses near the sample)--are critical for clear, sharp observations. Even tiny particles of dust, fingerprints or oil can cause images to be blurred, making it difficult to see bacteria, plant structures or cells. The right way to clean lenses protects the delicate coatings on them (a thin layer which boosts image clarity) and provides reliable results. Here's an easy, safe guide.
Why proper lens cleaning is important
The light is scattered by dust or debris on lenses, resulting in fuzzy images. Uncleaned fingerprints, which contain oil and sweat, or sample residues (like cell culture liquid) can adhere to lenses over time and cause damage to their coating. The wrong tools, such as rough paper, can permanently scratch the coating. This will ruin the lens and force expensive replacements. Correct, gentle cleaning will keep your lenses in great shape for many years. You can trust the images you see when you use a microscope.
What You Will Need
Use only a few simple tools that are safe for your lenses. Never use items from the home, such as paper towels or cotton ball. To remove dust, use a rubber air blaster (a small bulb which blows air). Second, use lint free lens paper, which is a thin, soft paper designed for optics. It won't leave fibers or scratch. Third, 70% isopropyl (rubbing alcohol) with distilled water. Tap water contains minerals that can leave marks. If you want to remove oily or sticky stains, mix them together in a ratio of 1:1. Pure alcohol can damage lens coatings so diluting is important.
Step-by-Step Cleaning Procedure
Work from the top to avoid dust getting on the cleaned lenses.
To remove dry dust, hold the air blower at a distance of a few centimeters from the lens. (Don't touch it with the blower). Blow air gently across the surface of the lens. This will lift loose dust without damaging the glass. Repeat this process 2-3 times to remove the majority of dry debris.
To clean light stains, such as fingerprints: Tear a small square of lens paper (5cm). It is best to fold it twice in half, creating a thick and firm pad. This will prevent your fingers from contacting the lens. Dip the edge in the alcohol-water mixture (just moist, not wet) to dampen it. Excess liquid could seep inside the lens and cause internal damage. Wipe the lens gently in a circular motion. Start at the center of the lens and work outward. To avoid spreading dirt, use a different part of the paper with each wipe.
For stubborn stains, such as dried sample residue: Repeat step 1, but apply pressure slightly harder (still gently!) Use a lens paper that has been soaked in alcohol. Avoid rubbing the lens back and forth, as this can spread residue or scratch the coating. Use a piece of dry lens paper to clean the lens again, removing all moisture.
Check your work by looking through the microscope to a white, blank surface (like an empty slide). Repeat the cleaning if you see any spots. Never skip this step as dirt left behind will impact your observations.
Do's and Don'ts
After each use, clean the lenses (a quick blow of air will prevent dust accumulation). Store the microscope under a dustcover to minimize dirt. Avoid using cotton swabs, tissue or paper towels as they contain rough fibers that can scratch the lenses. Use only a small amount of liquid. Alcohol or water in excess can damage internal components. Do not press too hard. Lenses are delicate and can be damaged by force.
Cleaning biological microscope lenses can be done easily with the correct tools and by following gentle steps. By taking a few minutes to clean your microscope, you can ensure clear images, and prolong the life of the instrument. This is important for student labs, classroom observations, and research.