Temporary Wet Mount (TWM) technique for observation of Living Organisms.


Table of Contents

What is Mounting?

A temporary wet mount is a laboratory technique that is used to observe the plant tissue or living microorganisms under a microscope.

In Mounting technique, the specimen to be observed is held on a microscopic slide by using a coverslip. After that, the slide is observed by using a microscope to examine the motility, cell structure, and shape of the specimen.


Types of Mounting Technique

There are different types of mounting techniques such as;

  1. Dry mount: 
  • The Dry mount technique is used to study pollen, hair, feathers or plant materials, etc.
  • In this method, the specimen is directly placed over a slide and then covered with a coverslip to protect it from dust.
  1. Wet mount or temporary mount: 
  • Wet mount or temporary mount technique is used to study the movement and behavior of living microorganisms. 
  • In this method, a drop of water is placed over a slide and then the specimen is placed within it.
  • After that covers it with a coverslip and observe under a microscope. The lactofuchsin mount is an example of Wet mount.
  1. Prepared mount or permanent mount: 
  • The Prepared mount or permanent mount technique is mainly used for pathological and biological research, where the specimen is needed to fix over the slide to prevent decay.
  • In this technique, the water content is removed from the slide by replacing it with paraffin, splitting it into very small slices by using a microtome, laying the slices on a microscope slide, staining the tissue by using different stains to expose specific tissue parts, clearing the tissue to execute it transparent and wrapping it with a coverslip and mounting medium.

Function of Cover Slip

  • The coverslip keeps the solid specimens pressed flat, and liquid specimens formed into a flat sheet of even thickness.
  • It keeps the specimen in right place.
  • It defends the specimen from dust and random contact.
  • It prevents the objective lens from reaching the specimen and vice versa.

Preparation of Temporary Wet Mount (TWM)



To make a temporary mount of a living organism in order to reveal the motility, structure, shape, and other components of the specimen.



In this method, the culture of a living organism is placed over a slide and then a coverslip is placed over this specimen. After that, the slide is observed under a microscope to confirm the specimen is motile or nonmotile. It also helps to determine the structure and shape of the specimen.


  • Old Culture Broth of Organisms (Rhizopus sp. Penicillium, Aspergillus, Spirogyra and Chlamydomonas, Volvox, etc.) or Material to be mounted.
  • Needles
  • Blotting paper
  • Compound microscope
  • Glass Slide.
  • Cover Slide.
  • Dropping Pipettes.
  • glycerine 


Temporary Wet Mount technique
Temporary Wet Mount technique | Image Author:
  1. Pace a drop of sterile water on a glass slide by using a Dropping Pipette.
  2. Then, pick the mounting material or culture of the living organism by using a sterile needle and transfer it to the drop of water.
  3. Now add glycerine to the mount and gently put the coverslip over the glass slide including the mount. Don’t smash the mount much.
  4. Use the Blotting paper to remove the excess amount of water and glycerine from the slide.
  5. Don’t put pressure over the cover slide because easily breakable.
  6. Now observe the slide by using a microscope.



Note the size, shape, and characteristics of the motility of bacteria.


  • Avoid using an excess amount of water.
  • Maintain the coverslip gently. Coverslips crack quickly so manage them nicely.
  • Practice proper staining procedure.
  • Don’t smash the mount too much.
  • Use a sterile needle to transfer the mount to the slide.



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