A wet mount slide offers a method for viewing microscopic specimens. This technique involves placing a sample in a liquid medium on a glass slide, then covering it with a thin coverslip. The primary purpose of a wet mount is to allow observation of living organisms in their natural, hydrated state, especially those that require a liquid environment or whose movement is best seen in fluid. It provides a temporary preparation for immediate microscopic examination.
Gathering Your Materials
To prepare a wet mount, gather clean, rectangular microscope slides, which serve as the base for your specimen. Coverslips, thin square or circular glass pieces, are placed over the sample and liquid to protect the specimen and the microscope’s objective lens. The specimen itself, such as pond water or plant tissue, is central to the observation. A liquid medium, like distilled water or saline solution, is used to suspend the specimen. A dropper or pipette applies the liquid accurately, and tweezers assist in handling delicate specimens.
Making Your Wet Mount Slide
Creating a wet mount involves careful steps for a clear view. Begin by placing a small drop of your chosen liquid medium, such as distilled water or saline, in the center of a clean microscope slide. The size of this drop should be slightly smaller than the coverslip you intend to use. Next, use tweezers to gently place your specimen into the liquid drop, ensuring it is fully immersed. For solid specimens, make sure they are thin enough to lie flat and not create excessive space under the coverslip.
Lowering the coverslip is a delicate step to avoid trapping air bubbles, which can obstruct your view. Hold the coverslip at a 45-degree angle, touching one edge to the slide just beside the liquid drop. Slowly and steadily lower the coverslip over the specimen and liquid, allowing it to fall gently into place. This angled approach helps displace air, preventing large bubbles from forming underneath. If excess liquid seeps out from under the coverslip, gently blot it with the edge of a paper towel to draw away the surplus.
Troubleshooting Common Wet Mount Issues
Issues can arise with wet mounts, but most have practical solutions. Air bubbles are a frequent problem, appearing as dark, circular obstructions under the microscope. Lowering the coverslip slowly at an angle significantly reduces their formation. If bubbles appear, gently tapping the coverslip or applying slight pressure near the bubble can sometimes move them to the edge.
Using too much or too little liquid medium is another common issue. If there is too much liquid, the coverslip may float or slide around, making it difficult to focus the microscope. Conversely, too little liquid can cause the specimen to dry out rapidly, distorting or killing living organisms. To correct excess liquid, place the edge of a paper towel near the coverslip to absorb the surplus. If the slide is too dry, a small drop of liquid can be added to one edge of the coverslip, allowing capillary action to draw it underneath. To prevent rapid drying, especially for longer observations, you can seal the edges of the coverslip with petroleum jelly or clear nail polish.
Common Wet Mount Observations
Once your wet mount is prepared, you can explore a variety of microscopic life and structures. Wet mounts are particularly suitable for observing living organisms found in pond water, such as protozoa like Paramecium or Euglena, which exhibit movement. You might also view plant cells, like those from onion skin, revealing cellular structures such as cell walls and nuclei. Human cheek cells are another common specimen, often stained to make the nucleus and cytoplasm more visible.
When observing your wet mount, place the slide on the microscope stage and secure it with the stage clips. Start with the lowest magnification objective lens, typically 4x or 10x, and use the coarse adjustment knob to bring the specimen into initial focus. Once roughly focused, switch to the fine adjustment knob for sharper clarity. As you increase magnification, remember that the field of view will narrow, requiring careful centering of your specimen. Adjusting the light intensity, often with the diaphragm, can also enhance contrast and visibility of transparent specimens.