Nearly every wine kit and wine making recipe has a different recommendation on how long primary and secondary fermentations are supposed to last. It turns out that there are a lot of variables that can affect how long each of these last. This means that there’s a good chance your wine will behave differently than what the instructions or recipe you’re following say should happen.
Primary fermentation is the more vigorous portion of the fermentation process during which time approximately 70% of your total amount of alcohol is produced. It will generally go by much more quickly than secondary fermentation. For more information on the differences between these two check out Primary Vs Secondary Fermentation.
So how long should each of these take? Let’s find out.
Primary fermentation usually takes between three to seven days to complete. It goes by much more quickly than secondary fermentation because wine must is a much more fertile environment for the yeast.
Sugar and oxygen levels are high during primary fermentation and there are plenty of nutrients. A happy and healthy yeast population can really consume some sugar at a rapid rate in an environment like this.
As fermentation progresses though the oxygen runs out, the sugar and nutrient levels drop, and alcohol starts to build up. This slows fermentation down. Listen this for more information on the yeast life cycle.
There is no definite sign or event that separates primary and secondary fermentation. So how long primary fermentation lasts has more to do with when you rack to a secondary fermenter than it does with some specific event taking place.
In general prmary fermentation is said to be over once your specific gravity has dropped to below 1.030. This is just a rule of thumb though. I consider my wine to be in secondary fermentation when it is ready to be racked to the secondary fermenter. This might be after three days or after two weeks, it depends on how fermentation is going.
If you make wine with fresh fruit, be it grapes or something else, you don’t want your wine to sit on that fruit any longer than five to seven days unless you really know what you’re doing with extended macerations. So regardless of where your specific gravity is you want to be off of that fruit lees before your wine begins picking up off flavors.
Suppose you’re making wine from a concentrate or from honey and you don’t have that fruit lees to worry about. At this point you can use the general rule of racking into a secondary fermenter when your specific gravity has dropped below 1.030.
How long secondary fermentation lasts depends on a handful of things. Not only does it depend on when you rack to a secondary container, it also depends on how agressive your yeast strain is as well as the wine’s temperature.
An aggressive yeast will power through a fermentation pretty steadily to the very end. This is especially true if you are making a dry wine. If, on the other hand you are using a yeast strain that has a 13% alcohol tolerance and you started with enough sugar to create a wine that is 13% ABV or higher it may take the yeast a few weeks or more to finish things up.
As I mentioned earlier once the oxygen has been depleted along with most of the sugar the yeast are going to be struggling quite a bit. Alcohol is toxic to yeast (it is their waste product after all) and as it rises it further challenges the yeast.
How to Tell When Fermentation is Over
This is a question that comes up quite a bit. The absolute best way to determine when fermentation is over and when you can move on to stabilizing, clarifying, and bottling is by using your hydrometer (here’s a video on how to get accurate readings: Using a Hydrometer for Making Wine).
As you know hydrometer readings drop throughout fermentation. Typically you’ll start with a gravity reading somewhere above 1.0 and wind up somehwere around 0.996 or so.
To see if fermentation is over you simply take two specific gravity readings a few days (or a week) a part and compare the readings. Of course you’ll need to correct your readings for variations in temperature (here’s how: Specific Gravity Temperature Correction Calculator), however, if you get two readings taken at two different times and the specific gravity has not changed during that time then you know nothing is going on and fermentaiton is over.
This is the only way to know for sure that fermentation is over. Some may suggest that you just wait a certain amount of time before bottling, however, your wine could still be sluggishly fermenting along. Don’t risk exploding wine bottles, use specific gravity measurements to gage your fermentations!
An Interesting Story
When I was making my strawberry melomel something strange happened. I mixed all the ingredients in (including real strawberries), pitched the yeast, and things started fermenting.
According to the recipe I was supposed to rack when my wine reached a specific gravity of 1.030 or less. Being that this was a melomel (sweetened with honey instead of wine) I assumed that the fermentation was going to take a little while. I decided to check my specific gravity after three days instead of doing it every day.
When I finally did check my specific gravity I was blown away as my reading was somewhere around 1.013 (see photo). I asked a fellow wine maker what he thought about racking and he suggested that I just wait it out and rack after fermentation ended.
What worried me was not that I missed a racking, that’s not a big deal. What bothered me was that I didn’t know if fermentation was going to complete before I needed to get off of those strawberries to avoid unwanted flavors of decaying fruit. If you rack your wine and the specific gravity is around or below 1.010 you can send the yeast into shock and you’ll wind up with a stuck fermentation.
Well, my yeast finished strong and by the seventh day my specific gravity was indeed below 1.000. Even if fermentation stuck it tasted fine with the sugars that were left in there so I went ahead and racked off of that fruit.
It was just really interesting to see a yeast blow through primary and secondary fermentation in a mere seven days! So this wine fermented completely in the primary fermenter and I racked into a secondary fermenter just to get off the fruit and let it clearn on its own. I’m sure I got a little more fermentation action out of that yeast but by in large the wine was 99% finished when I racked it.
My other meads have been the exact opposite. I usually let primary fermentation go on for two or three weeks and secondary fermentation can linger on for another month after that in the carboy. Not this time I guess.
The key points to take away from all this to realize that there is no clear demarcation between primary and secondary fermentations. When you switch from one to the other should be governed first by the need to rack if you have fresh fruit present and if not then use specific gravity measurements to determine when to move.
And again, fermentation is only over when your hydrometer says it’s over (two subsequent readings that are the same). This is true provided your fermentation didn’t get stuck which is also determined by using your hydrometer.
What About You?
Do you have any strange fermentation stories? Please share them in the comments if you do. We could all learn from your adventures!