Primary fermentation involves rapid yeast growth and activity as the yeast population converts sugar into alcohol. Up to 70% of the total alcohol is produced within the first 3-5 days as the yeast thrive on available sugar and oxygen. Secondary fermentation occurs as the yeast population declines due to depleted oxygen and sugar, slowing converting the remaining 30% of sugar over 1-2 weeks.

1. Primary Fermentation

2. • This stage starts as soon as you add your yeast to the must.
• During this stage the yeast population is growing rapidly.
• You know you’re in the primary stage because there’s a lot of visible
activity.
• There’s often a lot of foam on top of the must and your airlock will be
bubbling.

3. Why?
• The yeast population growing really fast because of the huge supply
of sugar, nutrients, and oxygen they lucked into.
• This is the most active and productive phase of fermentation.
• In fact up to 70% of the total amount of alcohol is produced during
this stage which only lasts about three to five days.
• After that we move into secondary fermentation.

4. Secondary Fermentation

5. • After a while things start to slow down.
• The oxygen has been depleted and the bulk of the sugar has been used up.
• Alcohol levels have risen to the point that it is affecting the yeasts ability to
reproduce and even survive.
• Many cells are dying off and collecting at the bottom of the fermenter.

6. • Secondary fermentation lasts between a week to two weeks.
• Obviously this is a much slower stage in the process.
• Primary fermentation – 3-5 days; 70% of our alcohol
• Secondary fermentation - >2 weeks; last 30%.
• The foam will disappear and you will see tiny bubbles breaking at the
surface of your wine.
• Your airlock will now be bubbling every 30 seconds or so.