Had no bad batches at home scale, but quite often get these events, when even replacing the lock with an open fermenter does not help. Only regular cleanups work.
This is extra notorious escapee, witbier (OG 1065) made to dump frozen berries that remain in my freezer. And my very vigorous yeast.
Just a single layer of thinnest foil to stop the light. This beer is quite light and needs this more than most, but I just wrap every fermenter that has any hops traces.
I estimated the real ecological costs at some point and it seems that they are near zero, even recycling the foil would make things worse, unless I just burn it for hydrogen. I do sometimes.
ha, I wasn’t concerned about ecological costs of the foil, though I bet you could just put an old shirt over it and have a reusable solution.
Those are quite transparent to harmful part of sunlight unfortunately. With light blocking devices, even a metal bell is less environmentally sound than foil - detergent and water to wash it occasionally have more footprint than a few meters of a few micron thick disposable aluminium.
I don’t really care about the environmental impact of aluminum foil, but maybe don’t leave your carboys sitting in the sun?
The light finds its way. Modern lighting (especially bright stuff I use for lab lighting) is less harmful than sunlight, but still harmful and broad spectrum. Compared to foil consumption on tools sterilization, this foil is nothing.