All About Microscope Slides
Microscope slides can vary greatly in quality and type. It’s important to choose your slide correctly, and it’s critical that you take care of it properly. Read on to learn more about microscope slides.
What is a Microscope Slide
The microscope slide is a piece of glass that holds a specimen under a microscope so you can observe it. They come in a range of sizes and thicknesses for different types of use. Many slides are made of common glass and optical quality glass, which is composed of soda lime or borosilicate. There are some slides made of specialty plastics and in fluorescence microscopy, fused quartz is used for ultraviolet transparency.
That’s not the only bit of variety you’ll find within slides; some are concave to hold water samples such as pond or tap water samples, some have rounded corners, others are marked with grid lines, there are frosted or enamel-coated slides, and some have a coating or electric charge to hold samples better. The slides with frosted edges are used for writing on the date or specimen name.
No matter what type of slide it is or its characteristics, they’re all designed to hold a specimen for examination.
Where is the Slide Placed on the Microscope
Below the objective lens on a microscope is a flat platform that is called the stage. If you’re wondering where slides are placed on a microscope, this is it. It makes sense that the subject you want to look at is put on a stage.
Most stages have metal clips on them, they’re called stage clips. These clips are used to hold the slide in place, and you’ll put the slide under the clips to secure it in place for better viewing. Advanced microscopes use a mechanical stage that securely holds the slide in place, offering you precise control over its movement.
How to Prepare a Microscope Slide
Learning how to prepare microscope slides is the next step. Preparing a slide is also called mounting. There are a few different types of mounts and knowing what you need will help you determine how to make microscope slides.
- Dry Mount: To do a dry mount, the specimen is placed on a slide. There might be a coverslip placed over the specimen to protect it but there isn’t always a need for a coverslip in a dry mount situation.
- Wet Mount or Temporary Mount: A wet mount is a bit more complicated than a dry mount. In a wet mount, the specimen is placed in a drop of liquid and then held between a slide and coverslip by surface tension.
- Prepared Mount or Permanent Mount: These mounts have undergone a complex preparation that involves fixing them to prevent them from degrading or decaying. The water in the specimen is then replaced with paraffin, and the specimen is sliced into thin sections for study. Oftentimes, the specimen is stained to highlight certain components before a coverslip is put into place. This is not something for a new microscope user to attempt.
- Strewn Mount: Strewn mounting suspends a sample in concentrated distilled water and is placed on a slide and then the water is allowed to evaporate so just the sample remains.
Most people will begin preparing their own microscope slides by doing a dry or a wet mount. It doesn’t matter what type of mount you’re attempting; you always want to start with a dry and clean slide. Throughout the entire process, you want to be as careful and accurate as possible.
If drawing up a fluid with a pipette, don’t collect too much and keep your solution next to your slide so you’re not moving around too much.
When lowering a coverslip, go slowly and lower one edge first and then slowly lower the rest of the glass. Do not "squish" or push on the stacked mount. Carry it by the side to avoid displacing the specimen or contaminating it.
How to Put a Slide on a Microscope
When you’ve prepared your slide and you’re ready to put it on the microscope, you’re going to want to be very careful handling the slide. Only hold it by the edges and carefully position it on the slide. Be careful not to tip it; you want to hold the slide flat or as level as possible.
Position the slide on the stage, so it rests directly below the microscope’s objective lens. Fasten the slide with the stage clips. Always start to focus with the lowest power objective lens clicked into position, raise the stage upward (or lower the nosepiece depending on the type of microscope) as far as it goes without letting the lens touch the slide or coverslip. Look through the eyepiece and move the focus knob until you have a clear view. You might then want to adjust the slide in very tiny increments to spot the best part of the specimen. After achieving focus, progress to the next highest power objective, incrementally moving through 4x, 10x, 40x, and 100x.
Once you’ve prepared your slide and placed it on the microscope stage, you simply need to set the focus and begin examining your subject.
Further Reading
You can learn more about microscopy below: