A wet mount slide is a method for observing specimens under a microscope, particularly useful for live samples. This technique involves suspending a sample in a liquid medium between a glass slide and a thin coverslip. It provides a temporary environment that helps keep organisms hydrated, allowing for the examination of their natural behavior and motility. This preparation is commonly employed in biology to view microorganisms, cells, or small tissue sections.
Gathering Your Materials
Gather the following materials. You will need a clean microscope slide and a thin, square coverslip is needed. A dropper or pipette for liquid transfer, your sample, and a suitable liquid medium, often distilled water or saline solution, are also required. Tweezers are helpful for handling delicate specimens.
Step-by-Step Preparation
Ensure your microscope slide and coverslip are clean. Place your specimen onto the center of the slide. If your sample is a solid material, use tweezers to position a thin piece of it, or if it’s a liquid, a small drop is sufficient. For solid samples, ensure the piece is thin enough to fit under the coverslip without causing it to wobble.
Add a small drop of liquid medium, such as water or saline, onto the specimen. The amount of liquid should be just enough to fill the space between the coverslip and the slide without overflowing. For some specimens, a specific liquid like saline may be used to suspend them.
Carefully lower the coverslip to avoid trapping air bubbles. Hold the coverslip at a 45-degree angle, touching one edge to the slide at the edge of the liquid drop. Slowly and gently lower the coverslip down over the sample, allowing the liquid to spread evenly as it settles. This angled approach helps to push out air from underneath the coverslip, creating a smooth, even layer.
Once the coverslip is in place, address any excess liquid. If liquid seeps out from under the edges of the coverslip, gently blot it away with the edge of a paper towel or absorbent tissue. If there is too little liquid and the sample seems dry, add a small drop of liquid to one edge of the coverslip, allowing it to be drawn under by capillary action. The coverslip should sit securely without floating, indicating proper liquid volume.
Troubleshooting and Clear Viewing Tips
Air bubbles are a common issue that can hinder clear observation by blocking the specimen or creating artifacts. If bubbles appear, gently tapping the coverslip or applying slight pressure can sometimes move them toward the edge. Ensuring the coverslip is lowered slowly and at an angle significantly reduces bubble formation. Another common problem is having too much or too little liquid, which can cause the coverslip to float or the sample to dry out too quickly.
To prevent the wet mount from drying out during longer observation periods, especially with living specimens, you can seal the edges of the coverslip. Applying a thin rim of petroleum jelly or clear nail polish around the coverslip’s edges can create a barrier against evaporation. For optimal viewing, always begin observation with the lowest power objective lens to locate your specimen, then gradually switch to higher magnifications for detailed examination. If focusing is difficult, try focusing on the edge of the coverslip or a small air bubble, then adjust the fine focus to your specimen.