Step 7: Cover With Cloth. NO LIDS!!!
Warning: NO LIDS! You must cover the vat with cloth.
If you have a lid over your vat, even a loose one, there will be moist air over the mother. There will be condensation on the lid and sides of the vat above the mother.
Mold will grow there and spread to the mother. The mother will die and possibly break apart.
If you see fuzz on the mother throw it away, clean all your vessels and let them dry out.
Bleach them or leave them in the sun if you want to be really careful.
Be very alert to this. Some types of mold make poisons.
Mold is dangerous, which is to say people have died from it.
The Russians call "the mother" "the mushroom", but there is no actual mushroom, fungus or mold in this complex community.
In my experience with helping people get started, mold is a bigger problem in California than in New England.
If you want to brew in a carboy (big jug with narrow neck, such as spring water vendors use) , you need to cut the top off so it's more like a bucket or vat.
I've seen it attempted in standard carboys and it ends badly, even if the jug is covered with cloth rather than a cap.
This fermentation is complex process controlled by the mother. It's an aerobic process at least on the surface layers, and the vessel should not be sealed or you'll end up with problems.
There will be another anaerobic stage later for those of you who want more fizz.