Wet Mounts


Introduction

Some samples can be placed directly under the microscope. However, many samples look better when placed in a drop of water on the microscope slide. This is known as a "wet mount." The water helps support the sample and it fills the space between the cover slip and the slide allowing light to pass easily through the slide, the sample, and the cover slip.

Challenge

Make a wet mount. Determine for yourself if an object looks better under the microscope mounted dry or wet.

Instructions

To make a wet mount place a sample on the slide. Using an eyedropper put a drop of water on the sample. Place one end of the cover slip on the slide and slowly lower the other end using the end of a toothpick. This will help to prevent air bubbles from getting trapped under the cover slip.

The water should just fill the space between the cover slip and the slide. If there is too much water and the cover slip is floating around, remove some water by holding the edge of a paper towel next to the edge of the cover slip. If there is too little water and some of the space under the cover slip is still dry, add more water by placing a drop right next to the cover slip. A little practice will help you learn how much water to add.

Now you are ready to compare wet mounts and dry mounts. Cut two small pieces of your hair. Place one on a slide and put a cover slip on it. This is a dry mount. Place the other piece of hair on the other slide and make a wet mount. Look at both slides. Draw a picture of both slides. Does one slide look better than the other? Repeat this exercise with other samples.

Further Explorations

Sometimes your sample is a little too thick for a wet mount. If the sample touches the cover slip and prevents it from lying flat, the water won't be able to fill the space between the slide and cover slip. You can fix this by cutting four small pieces of a material that is thicker than the sample and use these to support the cover slip. Plastic from a milk container works well. Make a wet mount as before but support the cover slip with the material.



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