A wet mount slide is a temporary preparation used in microscopy to observe specimens, particularly those that are living or transparent. This technique involves suspending a sample in a liquid medium, typically water, between a microscope slide and a coverslip. Its purpose is to allow for the examination of specimens in their natural, hydrated state, facilitating the observation of movement, cellular processes, and fine structural details.
Gathering Your Materials
You will need a clean, flat microscope slide, which serves as the base for your specimen. A thin, square or circular coverslip is placed over the sample, protecting both the specimen and the microscope’s objective lens. The specimen itself can be a drop of pond water containing microorganisms or a thin slice of plant tissue.
A liquid medium, most commonly distilled water, is applied to the slide to suspend the specimen and fill the space beneath the coverslip. This liquid helps to prevent the sample from drying out and improves optical clarity. To precisely transfer the liquid, a dropper or pipette is necessary, allowing for controlled application.
Step-by-Step Preparation
Place your chosen specimen directly onto the center of a clean microscope slide. For liquid samples, such as pond water, a single drop is generally sufficient. Solid specimens, like a small piece of a leaf, should be very thin and flat to allow light to pass through them effectively during observation.
Add one small drop of your liquid medium, usually water, directly over the sample. The amount of liquid is important; too much will cause the coverslip to float and slide, while too little can lead to air bubbles or a dried-out specimen. The goal is to fully immerse the sample without creating excessive overflow when the coverslip is applied.
Carefully lower the coverslip over the specimen and liquid. Hold the coverslip at a 45-degree angle with one edge touching the slide, just next to the drop of water. Slowly lower the coverslip using a dissecting needle or similar tool, allowing it to fall gently into place. This technique helps to push air away from the center of the slide, minimizing the formation of trapped air bubbles.
As the coverslip settles, the liquid should spread evenly to the edges, creating a thin, uniform layer. If there is excess liquid that seeps out from under the coverslip, it can be carefully blotted away with the corner of a paper towel. This prevents interference with the microscope’s stage and keeps the slide tidy for viewing.
Achieving Clear Views
Successfully preparing a wet mount often involves attention to detail to minimize common issues that can obstruct clear observation. One frequent challenge is the formation of air bubbles, which appear as dark, circular objects with thick, dark edges under the microscope. Lowering the coverslip at an angle, as described, helps to displace air and reduce their presence, leading to a clearer field of view.
The amount of liquid used is another important factor for optimal viewing. An insufficient amount of liquid can cause the specimen to dry out quickly, distorting its appearance and potentially damaging it. Conversely, an excess of liquid may result in the coverslip floating, making the slide unstable and difficult to focus. A thin, even layer of water beneath the coverslip ensures consistent optical properties.
Ensuring the specimen is sufficiently thin is also important for light transmission and resolution. Thicker samples can appear opaque or out of focus, as light cannot pass through them effectively. Gentle handling of the coverslip during placement prevents it from breaking or shifting, maintaining the integrity of the preparation.