Curds and Whey

I am attempting to make curds and whey for the first time. I bought a quart of nonhomogonized whole milk (in a glass bottle) and it is currently sitting out. It has been about two days now and nothing has happened. The bottle is completely filled--does it need room to seperate? Also, I have left the top on the bottle--should it be open or covered with a cloth rather than the sealed top? Thank you for any help.
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