Question

Why are agar plates turned upside down when incubated?

Answer 1

Before they are inoculated and incubated, agar plates are turned upside down so that any condensation that might be present on the lid does not drip down into the culture medium.

Answer 2

They are turned upside down because there might be condensation on the lid and turning it upside down would prevent it from dripping into the culture medium.