How to Make Agar Plates

An agar plate is a Petri dish that contains a growth medium solidified with agar, used to culture microorganisms


  • 750 ML Hot Water: Distilled, Purified, or tap.

  • 15 Grams Agar-Agar: To obtain the desired jello-like consistency, we use a substance called agar-agar. It is derived from red-algae and can be purchased at Asian grocery stores or anywhere that sells laboratory supplies. Try to find it in a powder form since we are dissolving it in water.

  • 15 Grams Light Malt Extract (LME): This is the nutrient source for the agar mixture. It comes in powdered and liquid form. I've only worked with the powdered version and recommend using it. LME is considered a brewing supply for beer.


  • Glass Vessel: Select the glass container with a lid to hold the agar mixture (Mason jar, booze bottle, Erlenmeyer flask, etc.)

  • Pressure Cooker: You'll need to sterilize the agar mixture for 45 minutes within a pressure cooker or autoclave.

  • Foil: Prevents moisture from seeping into the mixture when pressure-sterilizing.

  • Digital Scale: For accurate measurement of ingredients, I suggest using a digital scale that measures a hundredth of a gram.


Mix together 15 grams LME + 15 Grams Agar powder + 750 ML Hot water and pour into an old liquor bottle with a hole in the cap covered with 2 layers of micropore tape. Pressure cook at 15 psi for 45 minutes, allow to cool down only until it is able to be handled and pour evenly into your sterile petri dishes. This part should be done inside of a still air box or with a laminar flow hood. Maintain a steady room temperature to minimize condensation.

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