Find the Dirt. Clean Only What's Dirty.
A quick reference for tracking down a speck in the view before you clean anything.
A speck or smudge in the view could be sitting on any of a half dozen glass surfaces. Cleaning all of them "just in case" spreads dirt around and adds wear to coatings that were fine. Four quick tests, done in order, tell you exactly which part the speck is on. The whole check takes less than a minute.
Do this, in order
- Rotate the eyepiece. Turn it slowly in its tube while you watch the speck. If the speck turns with it, it's on the eyepiece.
- Move the slide. Nudge the stage a little. If the speck moves with the specimen, it's on the slide or coverslip.
- Change the objective. Click to the next one. If the speck disappears, it's on the objective you just left.
- Raise or lower the condenser. Small moves are enough. If the speck blurs or shifts, it's on the condenser or a filter.
- Clean only that part, then look again. Use fresh lens tissue and work from the center out.
Avoid this
- Cleaning every lens "just in case." It spreads dirt and adds wear to coatings that didn't need it.
- Wiping with a sleeve or paper towel. Both scratch optical coatings. Use lens tissue.
- Skipping the order. Each test rules out one part of the light path. Out of order, the answer gets muddy.
- Opening the microscope. Dust inside the head or on a prism needs a technician and the right tools.
- Blaming the objective first. Most specks turn out to be on the eyepiece or the slide.
Still there after all four?
If the speck stays put through every test, it may be inside the head, on a prism, or in a camera port. Don't open the microscope. That's an internal cleaning job, and it's one we handle every day.
The habit, every time
Rotate the eyepiece
Move the slide
Change the objective
Move the condenser
Image hazy rather than spotted? See Hazy Image? Check This First. For eyepiece cleaning, see Clean the Eyepiece. Don't Scratch It.
Play it as a game
Practice the four tests on a 3D microscope. Play Find the Dirt on a phone or computer, or in the Meta Quest browser for VR.
Watch it in a minute
Speck won't budge after all four tests? Send us an SOS. We'll take it from there.
Need hands-on help? See our microscope repair and maintenance service in Houston.
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