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How to prepare microscope slides

Last Updated: 06.12.21


For those that don’t know it, microscope slides are made from either plastic or glass and are used as support for the samples that are being observed under a microscope. However, according to the specialists, one cannot use the same types of slides for, let’s say, both a digital microscope for Mac and a classical optical instrument.

Because we are well aware of this issue, we have put together some practical pieces of information that you should take a look at before using your microscope. In short, this article was composed as a guide that can help you understand what is the correct manner in which one has to prepare microscope slides.


Wet mount slides

If you are planning to study living samples, it is a well-known fact that you have to use wet mount slides. These mounts have a similar design to that of a sandwich. Therefore, the bottom layer is the slide that contains the sample. Then comes the liquid sample and lastly you have plastic or a glass coverslip.

This latter layer is said to reduce liquid evaporation and to protect the lenses of your microscope from coming in contact with the given sample. To prepare this type of slide, one has to follow a simple process.

First, one has to set a drop of liquid or the liquid sample (glycerin, water, etc.) in the central part of the sample. Next, if the sample is not positioned correctly, use a pair of tweezers to place the sample in that drop of liquid.

The following step that one has to do take requires him/her to place the coverslip over the sample. When doing so, first place just one of the sides of the respective coverslip and make sure that its edge reaches the slide.

As you lower the coverslip, keep your eyes on the sample and make sure that no air bubbles are formed. To avoid bubbles, some specialists recommend that one applies the coverslip at an angle.

If you are examining organisms that are known for moving at a fast rate that obstructs you from studying them, it might be best that you add a drop of a substance called Proto slow before placing the coverslip. This way, you won’t find observing the organisms’ movements difficult or impossible.

Keep in mind that, as the liquid from the margins of your slide evaporates, the living organisms from the sample start to die. If you want to make sure that this process does not start immediately, you can add a small quantity of petroleum jelly to your sample before adding the coverslip.


Dry mount slides

Any new handheld microscope that allows one to examine dry samples surely makes use of dry mount slides. If you own a compound microscope, it is advisable that you prepare a sample that is flat and very thin. However, if you have a dissection scope, you shouldn’t worry about this aspect.

In order to prepare a dry mount slide, you should lay it on a surface that is flat. Next, by using tweezers, make sure that you place the sample on the slide. Last but not least, add the coverslip over the sample. If the situation requires it, you can study a sample without placing a coverslip over it. Still, whenever doing so, make sure that it does not come into contact with the microscope’s optics.

Whenever your sample is moving, or it won’t stay fixated on the slide, some specialists recommend that you use nail polish to secure it in place. This method is known for creating semi-permanent slides. In order to re-use the slide make sure that you use nail polish remover to clean it first.


Blood smear slides

If you find yourself having to examine a liquid that is too thick or too colored and you find it challenging to catch the details that you are interested in, you should try the blood smear technique. The name of the technique comes from the fact that blood (but also semen) are analyzed in this manner.

The process of creating blood smear slides is quite simple. A small drop of the liquid sample should be placed on the given slide. Then, a clean slide should be held at an angle to the prior slide. The edge of the slide must then come in contact with the drop. Next, a line of liquid will form on your slide. At this point, use the second slide to create an equal smear of liquid.

During the process, it is best that you do not apply any type of pressure as this might damage the sample. Once you’ve completed this step, place a coverslip on the resulting smear or wait until the slide dries.


The advantages of using stain slides

Another topic that you might be interested in has to do with the benefits of working with stained slides. The main advantage of these slides is the fact that the resulting smear makes easier for one to actually see the details that are otherwise more difficult to observe.

As a plus, because they use special substances such as crystal violet, iodine and methylene blue, the resulting contrast of the sample is oftentimes greatly improved.

By following the mentioned slide preparation techniques, we are sure that you’ll be able to examine all types of sample, without worrying about their clarity. So, don’t waste any more time and start exploring!



Ioana Moldovan

Ioana’s professional experience in the optics field has helped her understand the value of passing her knowledge forward. Her curious personality helps her gather useful information for her readers and her goal is to make technical information fun and accessible to everyone.

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