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 You will need 1.2 grams (approximately half a teaspoon) of agar powder for every 4-inch petri dish you wish to use. 2  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. 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.