Description: A 3L filter-patch spawn bag fully colonized with bright white Psilocybe cubensis mycelium, on a clean lab bench, science-forward and tidy. How to Use a 3L Colonized Spawn Bag: Spawn to Bulk, Step by Step The single most contamination-prone stage of a grow is the one at the very start: sterilising grain, inoculating it, and nursing it through two weeks of colonization while every opened lid is a chance for mould to get in. It’s where most beginners lose a batch —