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.
Agar is the jelly-like substance used to culture bacteria. It is made from a type of red algae which provides an ideal growing surface for many different types of bacteria. Some types of agar contain added nutrients (such as sheep's blood) which help to promote more vigorous bacterial growth. 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.