• Universals or bottles containing larger volumes (see Note) of sterile molten nutrient agar (at 55°C)
  • Sterile plastic Petri dishes
  • Bunsen burner and mat

Note: if larger volumes of agar are to be poured, lay out the appropriate number of sterile Petri dishes and flame the neck of the bottle before each plate is poured.


  1. This method is written for right-handed people. If you are left handed, please reverse handling instructions.
  2. Wear a lab coat and use eye protection.
  3. Label the empty sterile Petri dishes on the base with name, date and type of agar. (N.B. if the lid comes off, the plate is no longer sterile and you must discard it).
  4. Light the Bunsen burner.
  5. Collect one bottle of sterile molten agar from the water bath. Check it is not too hot and that it has not started to solidify.
  6. Place a Petri dish right way up on the bench.
  7. Check that the top of the bottle of agar is loose.
  8. Hold the bottle of agar in the left hand.
  9. Unscrew and remove the cap of the bottle with the little finger of the right hand.
  10. Pouring platesFlame the neck of the bottle.
  11. With the right hand lift the lid of the Petri dish a little and gently pour in the molten agar.
  12. Image 1     image 2
  1. Replace the lid of the Petri dish.
  2. Replace the cap of the bottle and put it down.
  3. Swirl the plate very gently to distribute the agar evenly. (N.B. The base of the plate must be covered, agar must not touch the lid of the plate and the surface must be smooth with no bubbles).
  4. Repeat for the other bottles and plates.
  5. Leave the agar to solidify.
  6. Once cool, turn the plates upside down.