1 A do-it-yourself approach for basic basement steps starts around $250-$350 for materials, and takes about 3-4 hours. 2  That's with standard lumber, such as pine; costs can go much higher with more expensive wood, such as oak.
Pour enough melted agar into each sterile plastic petri dish to cover the bottom - about 1/8 to 1/4 deep. Replace the lid immediately. Place agar plates on a counter top to cool and set. Agar medium will set like stiff gelatin at room temperature. The agar medium is now ready for storage or use.
1. Introduce bacteria to the petri dishes. Once the agar solution has hardened and the petri dishes are at room temperature, you are ready for the fun part-introducing the bacteria. There a couple of methods of doing this-through direct contact or through sample collection. In a heat proof dish or bowl, stir half a teaspoon of the nutrient agar powder into 60 ml (approximately 1/4 cup) of hot water. 2  Multiply these quantities for however many petri dishes you plan on using.