During my soapmaking, I usually have the soap in the time in the mold open to air, as I usually only do one batch with one type of essential oil each time. However, recently I have up to two batch of soap with different essential oil in the time in the mold kept close to each other. To prevent confusion, I lightly cover the mold (though it is not airtight or anything like that). I think I saw the soap hardened a lot slower, though I can't be sure about it. Hence I am curious with others who may have experience with this. Does the soap during time in the mold need to have full contact with air? Does it hinder the hardening if I keep the soap in the closed situation?