About Flotation Solution

Fecal flotation is based on the principle that parasite eggs have a lower specific gravity than the flotation solutions used to float them.  In other words, eggs float to the surface because they are lighter than the fluid used as a flotation solution. Notice in the image how the glass with the flotation solution floats the egg, while the egg in plain water will sink.

Flotation solution vs. plain water illustrating how eggs float.

Fecal flotation solutions vary in specific gravity depending on formulation, typically they are used in the range of 1.18 to 1.27. Most parasite eggs have a specific gravity of 1.05 to 1.20 making them less dense than the flotation solutions used, allowing them to float to the top of the flotation solution. The majority of fecal debris has a specific gravity greater than 1.20 causing it sink to the bottom of the slide chamber.

Want to make more flotation solution? Simply add 3/4 cup of kosher salt to your 16 oz Eggzamin Flotation solution bottle. Fill to the cap with warm water and shake well. 

Some sediment on the bottom of the container tells us we have reached appropriate saline saturation. If you plan to make your own flotation solution, or you will be storing the solution for long periods of time, it is important to check the specific gravity with a hydrometer. We are looking for specific gravity ranging from 1.20 to 1.25.

  • If specific gravity is too high, additional water can be added.
  • Store flotation solution at room temperature.
  • Do not refrigerate as additional solute will precipitate.

Note: Although it is possible to prepare solutions with a specific gravity higher than 1.27 however there will be osmotic distortion which makes it more difficult to identify the organisms. Additionally, fecal debris will also float making the sample hard to read.