Don't cover vessel during primary fermentation?

[GabrielKnight]

Reading on this 'winemaking 101':
http://www.eckraus.com/wine-making-101.html

<The primary fermentation is also called an aerobic fermentation
because the fermentation vessel is allowed to be opened to the
air. This air plays an important roll in the multiplication of
the yeast cells.

Here's how important. The little packets of yeast that is
generally called for in a five gallon wine recipe will typically
be multiplied up to 100 to 200 times during the few days of
primary/aerobic fermentation. Without air this multiplying stage
is hindered. That is why it is important that you do not use an
air-lock during the first few days of a fermentation and allow
the fermentation to be open to air.>

Its been years since I've been into homebrew, but I don't remember leaving the carboy uncovered for the 1st week or 2. Is this the right way to do it?

Edit: Wrong forum, sorry!

[oblivious]

The O2 is require by the yeast to produce sterols, fat like compounds not to dissimilar to cholesterol for the cell membranes production

[GabrielKnight]

So to confirm do you leave the lid off or use an airlock during primary fermentation?

[GabrielKnight]

I can now understand the benefits of letting some co2 in - thanks!

But doesn't it also let in the dreaded 'vinegar fly' and other tiny contaminants? How come its considered safe for the first couple of weeks, and then not?

[delboy]

The CO2 blanket that the yeast will have created will slowly dissapate in a fermenter with a lid placed on loosely, this leaves it prone to oxidation (cardboardy taste) by putting it under an airlock in secondary and snapping the lid on tight you hopefully retain the CO2 blanket and thus protect it from atmospheric air and oxidation, hope that helps

[steve_flack]

So to confirm do you leave the lid off or use an airlock during primary fermentation?

I ferment under airlock as I ferment in a garage frequented by creepy crawlies.

[lockwood1956]

You need O2 in there for the first part of the yeasts life, where they multiply to form a viable colony, they wont do this from the O2 in the must (well not very well anyway) once they have become a viable colony, and have also inverted the sugar (happens in this phase too) then they will begin the anaerobic phase where they dont need oxygen..... they feed on the sugar in the must (at this point you can cover the fermenter or transfer to demijohn)

hope this helps
regards
bob

[awalker]

I do as Steve_flack and ferment under an airlock in a garage.
A co2 blanket is not going to stop the huge spiders crawling into the fermenter.