Smear Fixation for Microscopy Studies

In this smear fixation for microscopy studies post we have briefly explained smear fixation of smear principle, objectives, requirements, fixation of smear procedure, uses and limitations.

Smear Fixation for Microscopy Studies

Many staining processes, such as Gram’s staining and acid fast staining, require a well fixed smear. If they are stained systematically, labelled appropriately, spread evenly, and fastened with care, a good smear will provide dependable information.

A uniform smear must be fixed or stuck over the slide after it has been prepared. Fixation of smear is the process of preserving and securing the internal and exterior structures of cells and microorganisms.


1. Clean glass slide

2. Wire loop

3. Burner or spirit lamp

4. Distilled water

5. Glass marking pencil

6. 70% methanol or Ethanol

7. Absolute alcohol

Fixation of Smear Procedure


Sterilize the wire loop by showing it in the flame, make it red hot and allow to cool. Place one or two drops sterile saline on a clean slide. Using the sterile wire loop pick up a small portion of the isolated Bacterial colony.

After making smears, the slides should be kept in a safe place to air dry. Protect the slide from flies and dust. If the smears cannot be stained immediately, they should be Fixed and stored in a covered box.

Heat Fixation

The air dried smear is fixed by passing the slide (Smeared slide up) rapidly over the burner by holding the slide with the thumb and index finger (Don’t over heat). The slide is them allowed to cool.

Alcohol fixation

Allow the smear to air-dry completely. Keep the slide on a staining rack. Add one or two drops of alcohol on the smear. Leave the alcohol on the smear for 2 minutes to dry the alcohol on the smear.


Heat Fixation

1. The aim of this heat fixing is to coagulate the aluminous material whereby the film adheres better to the glass slide and thus may not be detached in the subsequent staining process. Heat fixation of smear is commonly used for Gram’s staining.

Alcohol fixation

2. This fixation of smear kills M. tuberculosis and is more bactericidal than heat fixation. Fixation of smear containing instracellular Gonococcus and Meningococcus with alcohol is advised.

Further Readings