You don’t have to worry too much during colonization, just a half turn from being tight really. There will be plenty of gas exchange if done so. But I always leave mine very loose during sterilization, tighten after bringing out to cool and solidify. And I usually finish my cooling upside down. After about an hour or so, the agar will have solidified so you can invert the jar without it losing its shape. This will help with excess condensation.
Edited by peacefrog, 05 July 2019 - 02:24 PM.