Microwave Preparation of C-Fern Powdered Medium

Using a Microwave to Prepare Basic C-Fern Powdered Medium Makes C-Fern Even Easier to Use!
C-Fern users who do not have access to an autoclave can successfully use a microwave to prepare Basic C-Fern Powdered Medium.

Although the lower temperatures and shorter times of microwaving cannot guarantee sterility to the degree that autoclaving does, this method has been repeatedly used to successfully prepare contaminant-free medium.


  • 1 Packet of Powdered Basic C-Fern Nutrient Medium
  • 1 L volumetric flask
  • Distilled or deionized water
  • 2 L Erlenmeyer flask with non-metal cover
  • Difco Bacto® Agar
  • pH meter
  • 1.0 N NaOH solution
  • Microwave


Each packet of powdered medium contains the nutrients for 1 L of medium.

While stirring or swirling, add the contents of the packet to a 1 L volumetric flask containing about 800 ml of deionized or distilled water. Rinse out the packet to be sure to get all the powder. Fully dissolve contents of the packet, then bring to 1 L volume.

Transfer contents of the volumetric flask to 2 L Erlenmeyer flask

Add 10 g Difco Bacto Agar.

Adjust the pH to 6.0 with 1.0 N NaOH.

Process the solution in a microwave unit as specified in the following table. You may need to compensate for microwave units of different powers by adjusting the suggested times. Plates should be poured ¾ full.

Be sure to use caution when heating and handling! Wear safety glasses, use gloves, and do not leave the microwave unit unattended!

Stepwise Procedure For 1 L of Basic C-Fern Nutrient Medium prepared in a 2 L Erlenmeyer flask1

Step Microwave Time
(for 1000W output unit)
State of Solution2Post-microwave
15 minuteshotremove, swirl
21 minuteboilingremove, swirl
315 secondsboilingremove, swirl
415 secondsboilingremove, swirl
515 secondsboilingswirl to mix and pour Petri dishes

1Be sure to use a vessel at least twice the volume of the medium.

2The solution will boil vigorously in Steps 2-5! The medium must be visually monitored constantly so that if it starts to boil over, the power can be reduced or the unit turned off briefly.

3It is important to thoroughly mix the medium by swirling the flask after each step and while pouring plates.

Thomas Warne