Agar needs to be boil for about 30 to 45 minutes, until agar liquefied. Then pour agar inside the petri dish, about half full. Make sure agar is fully liquefied, or it will have bubble spots in agar.
Make sure all four Petri dishes are half full. Seat agar plates out for room temperature for about one to two hours, end then place them in the refrigerator.
Agar plates should ready and use in about a week