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.
You will need as much agar as you need, but dont use less than 1.2 grams (approximately half a teaspoon) of agar powder for every 4-inch petri dish you wish to use. 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.