Preparing a Wet Mount Slide

Make sure you’ve completed the How to Use a Microscope activity before you start here!

Anytime you have a specimen that needs water to live, you’ll need to prepare a wet mount slide. This is especially useful for looking at pond water (or scum), plants, protists (single-cell animals), mold, etc. When you keep your specimen alive in their environment, you not only get to observe it, but also how it eats, lives, breathes, and interacts in its environment.

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The first thing you need to do is collect your pond water. Make sure it has lots of good stuff in it! You’ll need a 20mL sample. Once you have it, place it on a table along with your microscope, slides, cover slips, tweezers, and dropper. If you’re using Protoslo (if critters are too fast, this slow them down for easier viewing), get that out, too. Open up your science notebook, draw a bunch of circles for drawing borders, and then watch this video:

Download Student Worksheet & Exercises

1. Place a slide on the table.

2. Fill the eyedropper with pond water and place a drop on the slide.

3. Place the edge of the cover slip on the pond water drop, holding the other edge up at an angle. Slowly lower the end down so that the drop spreads out. You want a very thin film to lay on the slide without any air bubbles or excess water squirting out. If you go have bubbles, gently press down on the cover slip to squish them out or start over.

4. Take time practicing this – you want the water only under the coverslip. Dab away excess water that’s not under the slide with a paper towel.

5. Lower the stage to the lowest setting and rotate the nose piece to the lowest magnification power.

6. Place the slide on the stage in your clips.

7. Focus by looking through the eyepiece and slowly turning the coarse adjustment knob. When you’re close to focus, switch to the fine adjustment knob until it pops into sharp view.

8. Adjust the light level to get the greatest contrast so you can see better.

9. Move the slide around (this is where a mechanical stage is wonderful to have) until you spot something interesting. Place it in the center of your field of view, and switch magnification power to find a great view (not too close, not to far away). Adjust your focus as needed.

8. Open your science notebook and draw a circle. Sketch what you see (don’t forget the title and mag power!)

9. When you’re done, lower the stage all the way and insert a new slide… and repeat. Find at least six things to look at. We’re not only learning how to look and draw, but hammering a habit of how to handle the scope properly, so do as many as you can find.

NOTE: If the critters you’re looking at move too fast, add a drop of Protoslo to the edge of your slide to slow them down (by numbing them). The Protoslo will work its way under the cover slip.

Exercises

1. Why do we use a wet mount slide?
2. Give one example of a specimen that would use a wet mount slide?
3. How do you prepare a wet mount slide?
4. Why do we stain specimens?
5. Give one example of a specimen that would use a stain.
6. What type of stain can we use (give at least one example).

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