Weigh your ingredients into a one-liter bottle or Erlenmeyer flask. Pour in about 800 mL of water, swirl like you’re stirring a martini, then top up to exactly one liter. Cap the bottle loosely—pressure needs to escape during autoclaving, but you don’t want a geyser.
If you’re making agar plates, add 15 grams of agar per liter. Stir gently with a magnetic stir bar; don’t whisk it like scrambled eggs. You want dissolution, not aeration.
Fun Fact: The Autoclave Is Your Best Friend
You must sterilize your medium at 121°C for 15–20 minutes under high pressure. No shortcuts. This kills any lurking spores or cheeky contaminants. If you don’t have an autoclave (hello, home lab weirdos), a pressure cooker works—just vent it properly. The time depends on volume; 500 mL takes about 20 minutes.
LB Broth Agar Media Preparation | Bacterial Growth Explained Step-by
After sterilization, let it cool to around 50°C before adding antibiotics or pouring plates. Hotter than that, and your antibiotics die. Cooler, and the agar will set before you can say “Petri dish.”
