Dirt, dust, and oils can build up on microscope lenses over time, producing poor-quality, blurry images. Luckily, you can restore image quality by cleaning the lenses carefully. The correct way to do this will depend on whether they are concave or convex lenses. Either way, it is important that you do it carefully and that you use the right tools so as not to damage the lenses. Once they are clean, there are some steps you can take to keep them in optimal condition so that your images always look clear and sharp.
Steps
Method 1 of 4: Clean Concave Lenses

Step 1. Dampen a cotton swab with a drop or two of lens cleaning solution
A cotton swab will help you clean the surface of a concave lens, which is curved inward. Make sure to use a lens cleaning solution or a solvent like acetone or xylene.
If you use a solvent like acetone, be careful not to get it in contact with plastic parts, since acetone will dissolve most plastics and paints

Step 2. Twist the wet swab gently from the center of the lens outward
To cover the entire lens with the cleaning solution, move the swab in a spiral pattern from the inside to the outside. Once you have swabbed the outer edge of the lens, you have covered the entire area.

Step 3. Dry the lens using a circular motion with the other end of the swab
To dry the lens, turn the swab over to use the dry end. Pass it over the lens in the same circular motion, moving it in a spiral pattern from the inside out.
Method 2 of 4: Clean Convex Lenses

Step 1. Dampen a piece of lens paper with a drop or two of lens cleaning solution
Make sure to use a specially designed lens paper for lens cleaning. While this paper is smooth and specially made for sensitive surfaces such as microscope lenses, it is best used in conjunction with a lens cleaning solution to avoid scratches.
In the case of very difficult to remove or sticky residues, you can use xylene instead of the mentioned solution

Step 2. Hold the moistened lens paper against the lens surface for 5-10 seconds
Higher magnification lenses (such as 10x) often use an immersion oil to produce sharper images. This step will help break down any oil residue present on the lens.
Lenses using oil immersion should be cleaned with lens paper after each use

Step 3. Press a piece of dry lens paper against the lens for a few seconds
To dry the cleaning solution, press a new sheet of lens paper against the lens. Avoid using paper towels or other disposable tissues to clean the lens, as they could scratch it or leave more dirt on it.
Method 3 of 4: Maintaining Your Lenses

Step 1. Wash your hands well before handling the microscope
To avoid transferring dust or debris to the microscope, wash your hands with soap and water. Then dry them well and put on some gloves.
Gloves will prevent natural oils on your skin from contaminating the microscope

Step 2. Use a manual air blower to spray air onto the lens
You can squeeze a handheld air blower (usually shaped like a bulb and made of rubber) to produce small bursts of air. Use it to gently remove any dust or dirt.
- You can purchase a manual air blower online or at electronics stores.
- You can also use a can of compressed air, but be sure to use one that does not contain cleaning chemicals, as they can damage the lens.
- Be very careful not to touch the lens with the tip of the can or the blower.

Step 3. Clean the immersion oil from the lenses after each use with lens papers
It is important that you clean them each time you use them, as the oil traps dirt and can slowly dissolve the glue on the lenses. Press a piece of lens paper against the lens to absorb the oil.

Step 4. Cover the microscope every time you don't use it to protect it from dust
A microscope dust cover will help prevent dust from settling on the device. Tuck in the edges of the dust cover or make sure it is zipped or snapped closed. Lastly, store the microscope on a flat surface to prevent it from tipping over.
Method 4 of 4: Inspect the Microscope for Dirt

Step 1. Check the outside of the eyepiece for debris
Because microscopes are sensitive and expensive equipment, avoid cleaning lenses unless absolutely necessary. Look through the eyepiece using each lens. If you see debris on all the lenses, the eyepiece is most likely dirty.
If this is the case, spray the eyepiece with compressed air and gently clean it using lens paper

Step 2. Move the slide from side to side while looking through the eyepiece
If the dirt is moving along with it, it means that the slide is the one that is dirty. If it stays in place instead, dirt could be on the eyepiece or lens.
If cleaning the outside of the eyepiece does not remove the dirt, it may be on the inside of the lens. It is best to take it to a professional or contact the manufacturer to take care of cleaning it

Step 3. Look through the eyepiece with each lens to identify the ones that are dirty
If the eyepiece is clean, but you still see smudges when you use it, look through the eyepiece with each lens. If dirt is only visible when using one lens, then that is the one that needs cleaning.
For example, if you see dirt when using the 4x lens, but not the 10x or 400x lens, it means that the former is the one that is dirty
Warnings
- If you suspect that the internal lens is dirty, take it to a professional service center to have it inspected and cleaned. It is best not to try to do it yourself, as the quality of the image may suffer if it is not done correctly.
- Only use high-purity cotton cloths to clean the lenses, as regular cloths can damage them.
- Clean the microscope lenses whenever you notice dirt. If you clean them too often, you increase the risk of damaging them.
- You can easily clean the lenses while they are attached to the microscope. Be careful not to remove them from the microscope while you are cleaning them, as you could damage them.