There is a bit of confusion out there as to what the difference is between primary and secondary fermentation. Sometimes secondary fermentation is confused with a second fermentation and other times malolactic fermentation. Let’s set the record straight.

Primary Fermentation

The beginning stages of primary fermentation.

A Primary Fermentation Bucket

Before we talk about secondary fermentation lets start at the beginning with primary fermentation. 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 like crazy.

Why? The yeast population growing really fast because of the huge supply of sugar, nutrients, and oxygen they lucked into. It’s like a party in there. Everyone is hopped up on sugar and bouncing off the walls.

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.

Secondary Fermentation

After a while things start to slow down. The oxygen has been depleted and the bulk of the sugar has been used up. Because of this the yeast population is no longer expanding. In fact life is getting hard for the yeast.

Secondary fermentation often takes place in glass carboys.

A Secondary Fermentation Carboy

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. This is one of the reasons we have to rack the wine after primary fermentation is over. We don’t want to pick up any off flavors from the dead yeast.

Secondary fermentation lasts between a week to two weeks. Obviously this is a much slower stage in the process. Primary fermentation took three to five days and produced 70% of our alcohol while secondary fermentation takes up to two weeks just to get the 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.

There is no identifying event that separates the primary stage from the secondary stage. When it happens depends on the grape varietal, sugar content, yeast strain, fermentation temperature, etc. In other words you just have to watch your airlock or the level of activity at the surface.

Secondary Fermentation is not a Second Fermentation

This is where it gets confusing. A second fermentation is where excess sugar not previously consumed by the yeast restarts alcoholic fermentation. Commonly this happens when a wine is back sweetened before all the yeast have died.

Some people mistakenly refer to malolactic fermentation as a second fermentation. I think it makes sense to differentiate between the two so that we’re speaking a common language. Malolactic fermentation is malolactic fermentation.

Second fermentations usually happen by accident except when making sparkling wines. Sparkling wines are bottled before the yeast is dead and a little unfermented grape must is added to give the yeast something to eat. In so doing the carbon dioxide produced is trapped in the bottle and we have bubbly. That’s the short version.

  • Maria

    Good morning Matt

    From what I understand (so far) the primary fermentation is done in an open bucket (without the lid) since the air plays an important role in the multiplication of yeast cells, it is an aerobic process; after 3-5 days you rack it into a carboy and place the airlock, the process becomes anaerobic, in this phase air exposure should be kept to a minimum. I got this information from


    • Hello Maria!

      You are correct, oxygen plays a very important role in the fermentation process up until the yeast has reached a healthy population. Once that has been achieved if we do not restrict yeasts access to oxygen it will not produce the alcohol we are looking for.

      Primary fermentations tend to be quite vigorous so as the yeast population grows and the volumes of carbon dioxide produced increase you reach a point where the carbon dioxide produces a protective blanket over the wine thus limiting its exposure to oxygen.

      Check out The Epic Rise and Tragic Fall of a Yeast Empire for more information on the yeast life cycle. This goes into the role of oxygen, why we use airlocks, and more. Understanding how the population grows, struggles, and then dies is very important to making great wines. Everything we do in the beginning is to facilitate this process.



  • willowbel .

    Hi matt Im a first time wine maker here and have just batched my first mulberry wine..firstly I did my primary fermentation with a lid and airlock as I had learned that the airlock can help determine when the primary fermentation is finished and ready for the second phase. So I did a SG reading on day two of fermentating and it read at 1.090 the second reading I did was at day 5 at that read 1.020 so I racked of the wine mashed the berries and added in the extra liquid into a new barrel and placed the lid back on with the airlock the instructions said to leave it like this for 6 months and racking 2 times in between, after this you can bottle the wine where it has to be left for a futher 6 months to allow the wine to if I do a sg reading after the 6 months before I go to bottle it and my sg reading is at 1.000 what will this mean, does it mean the fermentation is complete and how will the wine go clear as it is still cloudy?

    • Hello willowbel! First of all, congrats on starting your wine making journey. I really hope you enjoy this first batch.

      As for your question, an isolated specific gravity reading of 1.000 won’t tell you much except how much. What is more useful is comparing two specific gravity readings to each other.

      Two identical readings taken a couple weeks apart means fermentation is over. If there is any difference between the two readings your wine is still fermenting. Make sure you’re correcting your specific gravity readings for temperature differences though or you could get a false indication that things are still fermenting.

      Here’s an article on temperature correction that you may find useful <a href="; target="_blank"Specific Gravity Temperature Correction Calculator.

      Wines can and do clear on their own. It takes longer than using a clarifier. Most wines clear in three to six months though if you have the patience 🙂

      I hope this helps. Keep those questions coming if you’ve got any!

  • Crash

    Hi folks. Should I rack my wine now that it’s been 7 days since I added the must to my demijohns? I bought my juice already pressed. The company adds the proper yeast to it when they press it. The bubbling has stopped almost completely with my reds and is still going a tiny bit with the white.

    • Hi Crash! I believe it is best to rack a wine when the specific gravity has dropped to between 1.030 and 1.010. If the SG is higher I’ll wait longer. If the SG dips below 1.010 in the primary fermenter I’ll wait it out and let fermentation complete where it is.

      Racking a wine at less than 1.010 SG can cause the yeast to go into shock and possible lead to a stuck fermentation.

      I hope this helps! -Matt

  • Margaret S

    Help. I have made wine once before and it turned out great. I am making apple wine from both fresh apples that I juiced and apple juice I bought. Everything was still perking really great on day three after yeast was added with a generous head on the yeast. Before adding the yeast my sg was 1.100. I didn’t check the sg until day 5 now when it quit bubbling and the sg is down to 1.00. This is bad isn’t it. I don’t know whether to rack it into the carboys now or if there is something else I should do before doing that. That is too low of a reading, right? I should have tested it on day 4 when the bubbling slowed down. I still have it in a 6 gallon bucket covered with a light towel. Please help. (5 gallons of juice)

    • Hi Margaret! I recommend getting your wine into a smaller container at this point. A 5 gallon carboy sounds like it would hold your wine nicely and keep the head space to a minimum.

      You may or may not see any further fermentation. That is dependent upon how tolerant your yeast strain is to alcohol. You’re currently at about 13.6% which is pretty good. It may go further but it may not. Give it some time in the carboy and see how it goes.

      If you take two specific gravity readings a week a part and compare them you’ll know if it is still fermenting. Two readings that are the same taken a week a part is a good indication that fermentation is over.

      Thanks for the question Margaret I hope this helps. -Matt

  • Hi Dileep! Great question. I would keep your wine in the container it is in until fermentation slows down noticeably or if it stops all together. How long that takes depends on your yeast straing, amount of nutrients, and the temperature of the wine. So it’s hard to predict.

    In general you’ll want to rack (siphon) the wine to a different container if the sediment gets to be 1″ deep or so. You didn’t mention if there was pineapple fruit in your must or not, if there is you only want to stay on the fruit for a maximum of seven days.

    I hope this helps! -Matt

  • Hi Walker, this is an interesting thing to happen. I’ve had the same thing happen when making a strawberry wine. I recommend you go ahead and rack the wine and start the clarification and degassing processes.

    Once primary fermentation is over you definitely want to get your wine out of the primary fermenter and into a carboy in order to reduce the head space and therefore oxygen exposure.

    I hope this helps Walker! -Matt

    • StuK

      Hello, I am new to making wine. I have my first batch in progress as I type. I went through the primary stage and have racked the in a 5 gallon carboy for secondary. However when I racked from the primary to the secondary my instruction did not mention topping off and have roughly 1/2 gallon of headspace. The wine fermented(bubbled for roughly 2 months in the carboy so I think its fine in regards to oxidation) but as I say “I think”. My instructions are supposed to make 5 gallons and right now I have 4 1/2. The wine is blackberry so I can’t just go and buy blackberry juice or blackberry wine to top off with. Should I top off with water at this point and should I rack it into another carboy, add to the current carboy or is it a lost cause at this point. Any advice is greatly appreciated. Thank you.

      • Hi StuK, I don’t recommend topping up with water. Only inert gases or a like wine that has been finished already.

        In a pinch I have been known to agitate the wine in the carboy with the airlock in place in order to release some suspended carbon dioxide from the wine. Using that as my inert “topping” gas I’ve displaced the oxygen in the head space.

        I do recommend bottling sooner than later though to minimize future risks of oxygen exposure.

  • Hi Mary! A specific gravity of 0.990 is not unheard of but it is at the bottom of the typical specific gravity ranges one expects to see.

    What was your original specific gravity? Knowing the original and final specific gravity readings can help paint a more complete picture of what you’ve got on your hands.

    How does the wine taste at this stage?

    Cheers! -Matt

  • Monty

    Mr. Williams,

    First thanks for the great article. I was looking for information
    on the primary fermentation process and what the steps are for determining when
    to finish out the fermentation in a smaller container (carboy).

    I have started a 6 gallon batch of Blackberry and Raspberry
    wine 7 days ago. I am aiming for a higher alcohol content of around 14 percent.
    Starting SG was around the desired 1.108 ish. And I measured today (day 7) and
    found it to be 1.045. Fermentation is still very active and it seems the party
    is still a rockin. The yeast I used is rated for up to 20 percent alcohol

    My question is this. Most posting I have read state to move
    the primary fermentation off of the fruit around day 6-7 into a smaller
    container. But I have also seen as stated in one of your comments to rack it at
    1.030 ish. Is it bad to leave the primary fermentation in the bucket on fruit
    until I actually reach the 1.030? I have heard that you can pick up off- flavors
    by leaving it on the fruit to long. Some even say get it off the fruit on day
    3. I understand it is taking longer because of the higher potential alcohol
    (sugar) level at start-up. I am just trying to figure out if I should remove
    the fruit now or let it ride.

    This is only the second batch I have made. So I am learning
    as I go.



    • Hi Monty, great question! I recommend racking at 6-7 days if on the fruit or when you reach 1.030, whichever comes first. Staying on the fruit beyond 6-7 days can result in off flavors in some cases as the fruit begins to decay. Racking when your specific gravity is less than 1.030 can potentially put the yeast in shock and your fermentation will stop. So monitor the specific gravity and rack when you reach 6-7 days or sooner if the SG reaches 1.030. I hope this helps!

  • G-Pain

    Hello Matt, my primary fermentation began with an Sg of 1.090 and a lot of activity, after day 5 secondary fermentation with transfer into carboy and Sg of 0.998, had some activity for two days and now airlock only burps every 3 minutes after day 4 of secondary fermentation. Should I wait the additional 6 days as instructions state or move to stabilising and clearing now? Or is limited activity normal in the secondary stage?? Thanks from a first time wine guy!

    • Great question, Secondary fermentation is a lot slower than primary fermentation. It takes a while to get that last bit of alcohol fermented.

      I recommend waiting and going by the instructions. If you bottle too soon you could end up with trapped carbon dioxide which isn’t safe unless you’re using champagne bottles.

      Your specific gravity could go as low as 0.990. Time is the best thing to give a wine. Incidentally it’s also the toughest thing as well.

      I’m glad you’re giving winemaking a go! Let me know how it turns out.

      Cheers! -Matt

    • G-Pain

      Hello Matt, can I degass my wine multiple days until the process is complete in the stabilising stage? Will removing the airlock multiple times to degass hurt the process and can the airlock tell you if degass is complete?

      • Another great question! You can degas over multiple days. Just be careful about oxygen exposure. Also, only do this if you haven’t yet added your clarifier. Stirring up settled lees that has clarifier in it will lead to a cloudy mess and you’ll likely have to add another clarifier to get it to clear after you’ve finished degassing.

        Cheers! -Matt

  • Ellabella

    Hi, I am very new to home brewing etc and I have some questions…
    I have been experimenting with fermenting fresh fruit juices. I tried with some pink grapefruit juice but it tasted terrible and yeasty. I left it to ferment for a week like I read. The visible fermentation had stopped two days before I tasted it. It is sitting in a cupboard a week later. My question is, is it savable or have I really messed it up?
    Also I had a go at making some hard apple cider yesterday. It is fermenting well. I also have some pineapple juice and are there any tips for making sure they don’t go wrong?
    Finally, how long should I actually wait to drink it?

    • Hi Ellabella, great questions! My initial thoughts on the grapefruit wine is that there could be an odd acid balance. Citris fruit has a lot of citric acid and not much malic or tartaric acid. When the acid balance is off you can get strange flavors.

      One question, where did this juice come from? Did you use store bought juice or did you press grapefruit? The reason I ask is that store bought juices are processed and sometimes have stabilizers added to keep them from spoiling on the shelf. This can interfere with the yeast and create off flavors.

      Yeasty flavors are typical in young wines and certain yeast strains can give off more yeasty flavors than others. Did you use a wine yeast? If so, which one? Bread yeast generally doesn’t produce a very good wine so switching to a wine yeast for your next projects could help a lot.

      Many fruit wines can be consumed within a couple months of bottling. They don’t tend to age for years at a time like grape wines can. I’d give the yeast flavors a few months and they’ll likely go down. As for what to do about the other flavors, I can’t really say without having tasted it myself. If the acid is too high you can lower it but without knowing the pH it’s hard to say if this is a problem. Some local wine making supply shops can test for basic chemistry and you may also get pointers from them if you stop by.

      As for pineapple and apple juices, again you want to make sure there are no stabilizers added so look for things like sorbic acid, potassium metabisulfite, etc on the ingredient list. Sorbic acid can prevent yeast from reproducing and they will struggle to ferment the juice. The stress on the yeast and the interaction with these chemicals can also cause off flavors and aromas to form.

      My best advice is to use wine yeast and ferment juices that are free of stabilizing chemicals. Please let me know if you have any more questions. Cheers!!! -Matt

  • Joe

    Hi I am new to wine making and am making a 1 gallon batch of strawberry wine. My question is I started with a sg of 1.085 and after 3 days in the primary fermentation I have a sg of 1.00. I used fresh fruit in a fruit bag. My question is should I let it finish in the primary or transfer to the carboy. I have read 10 different contordicting articles.

    • Hi Joe, when fermentations go that fast I tend to let them finish out. I will remove any fruit after 5-7 days or when I rack, usually when the specific gravity is between 1.020 and 1.000.

      I have had a strawberry melomel that did what you are describing and I let it ferment dry in the primary. I was using EC1118 and it was so aggressive that in 5 days the specific gravity was down around 0.995 or so.

  • Joey Raso

    Hi guys, I just pressed my grapes today and added them to the damijans, I left enough room so it can foam but I set aside extra juice to top it up. When should I add the extra juice?

    • Hi Joe, whatever juice you add is going to renew fermentation as you’re adding additional sugar. This is fine but expect an increase in activity after adding it. Since you’ll be in the carboy I would wait until the specific gravity is around 1.010 to add it.

  • winediva33

    hi so I started my process about a month ago and have a week ago poured into second fermenter and got the clear wine off of the sediment in the bottom and thinking about during the pout off process again cause there more sediment in the bottom again how sure wait to bottle it?

    • I recommend racking every two months or when you see 1/2″ of sediment in the bottom of the carboy. You can bottle once you no longer see sediment collecting in the carboy.

      Alternatively you could add a clarifier which will know out the sediment much more quickly. You have to be sure fermentation is over though as it will continue to throw sediment as long as it is fermenting.

  • Robert Saggese

    Morning Matt, bit of advice , all natural wine maker here Trebbiano white grapes no additives sugar water yeast nothing ! i pressed 60 lts on 13th , Brix 21 SG .090 temp 18 deg. started fermenting 16th tested it today 23rd 8th day fermenting and its sg .022 at 18 deg c, question is still very sweet, i prefer a dry wine at which stage do i need to pull this as per SG etc , to place in 54 ltr Demijohn and then will it need a water/air trap to continue second stage ferment or cap it complete free from air , don’t want that bitter taste, not confident on whites any advice bud, also got 250 ltrs Montepulciano red on the go but all ok at the mo fingers crossed ! cheers Rob

  • Patrick Williams

    Hi Matt! What a wonderful resource! Finally checking this (winemaking) off my list 🙂 I stumbled into 100lbs of fresh plums & spent two days washing, stoning, & prepping them for my inaugural batch. I wound up with 80 lb. of gorgeous Empress? or Damson? fruit. My wife & I ran it thru the manual juicer & kept the skin etc., Placed that in nylon hose to add to primary. I added 40 lb sugar, 10 tsp pectic enz., 20 tsp. Nutrient, and one other ingredient (Forgot) and put it all into a 32 gal Rubbermaid Brute PDHE Primary, & stirred heavily. 24 hr later I added 6 pkg of wine yeast recommended by fella @ supply store to 4 oz. of tap water @ 105 deg…. Turned by back for ten min & it promptly overflowed. I took that as a sign it was working. Added it to my 20-25? gal of yum & stirred again, squeezing the beegeesuz out of the nylon sacs.
    my questions…..
    1. Is 6 pkg yeast enough?
    2. I made a 3 ft. long stir tool for my hand drill similar to a paint stirrer. Almost emulsifies…is that bad or good?
    3. I set a 25 lb bag of sugar on the lid of the trash can. unlikely that it’s air tight. Should I remove the weight?
    4. My intent is to fill 5 gal carboys after 3-5 days. MUST they be glass?
    5. What range of hydrometer should I have?

    I confident this is a new addiction. Though my hands are shredded, the excitement of finally making some wonderful wine (PLUM for goodness sake!) made the 10 hr of stoning the plums no problem. I just want to get this right & can’t wait to run another batch. I’m DEFINITELY patient & willing to let this wine age out. 🙂 Thank you Thank you Thank you for your help.

    • Hi Patrick, thanks for reaching out with your questions! It sounds like you’ve got a pretty solid wine making process from what you describe there. Here’s my answers to your questions:

      1. Recently I looked into this for a D47 yeast but it should be comparable for other strains. By my math it required between 1.0-1.5 grams per gallon thus if you are fermenting 20-25 gallons the sweet spot is going to be between 20-40 grams. Six 5g packets puts you at 30 grams which is perfect. Well done!

      2. Your degassing tool sounds fine. The only two things you need are to be able to easily sanitize it and that it agitates the wine enough to release suspended CO2.
      3. Having the sugar on the lid isn’t a bad idea if you’re worried about pets or something messing with the lid. It may also hold it tight enough to keep flies out. It’s okay to keep your wine stored this way for about 5-7 days at which time I would expect it to slow down and move into secondary fermentation. At that point you’ll want to rack off the fruit (if there is any in there) and into a container such as carboys where you can attach an airlock.
      4. No, you can use PET plastic carboy as well. Just be careful not to scratch the plastic when you clean them out. The scratches can become great places for spoilage micro-organisms to hide out.
      5. My hydrometer goes from 0.982 up to 1.160 which envelopes the winemaking brix / SG range quite nicely.

      Winemaking is easy to get hooked on! I’ve come to find that an empty fermenter is a very sad sight. Patience is definitely the hardest part of winemaking but if you keep your fermenter busy it’s a lot easier to pass the time.

      I’m always happy to help Patrick. Cheers!


  • Matt

    Hi there! I am making a gallon of wine from concentrate. I started my primary fermentation in a bucket with an airlock. I racked it on day 4 – it had mostly stopped bubbling. After I racked it into a glass carboy it bubbled every 10 seconds or so then slowed down over the next few days. It’s only been 5 days and it’s stopped bubbling. I expected this would take more like 3 weeks. Should I rack it now or is it ok to wait? There isn’t much sediment on the bottom, maybe 1/8-1/4 inch.

    • Hi Matt, nice name 🙂

      From what you describe it sounds like your wine has fermented quite well. The true indication of whether fermentation is over or not is whether or not your specific gravity is still changing. Over time fermentation slows way down and, as you say, may take up to three weeks to complete.

      However, if you used an aggressive yeast and had lower sugar levels I could definitely see fermentation being completed after just five days. If you let me know what your original and current specific gravity readings are and what yeast you used I can help you determine if you had a fast ferment.

      Your wine should be fine in the carboy for up to a couple months provided the head space isn’t too much (you don’t want a bunch of oxygen in there).

      Even if you don’t have an original specific gravity reading you could pick up a hydrometer and take a reading now. That will tell us part of the story. Also, if you take two measurements a few days apart and they are the same then fermentation is definitely over.

      I hope this helps Matt! Let me know about the gravity readings and yeast strains and we can work out where you are in the winemaking process. Congrats on your first batch!

      Happy fermenting,


      • Matt

        Hi Matt! Thanks for the reply. The original SG was 1.085. Before the first rack(ing?) it was 1.010, and I just tested it and it was 0.990. There was about 1/4″ of sediment on the bottom.

        I used Red Starr yeast – I forget the type, but I believe it was for red wine. Red package I think.

        Oh, and I was a little grossed out to find a couple small gnats in the air lock. I’m not sure how bad that is… Thanks again!

        • Hey Matt, thanks for the update. With a current gravity of 0.990 I would say your wine has finished fermenting completely. You racked right on time at 1.010 too so well done.

          Red Star makes good strong yeasts so it’s no surprise that it would ferment your wine in that amount of time.

          Gnats in the airlock is no fun but at least the airlock was there to protect your wine from the gnats! They have been known to carry acetobacter which is a bacteria that turns wine into vinegar.

          From here you can sit on the lees for up to a couple months or you could rack into another container, degas it, and add a clarifier if you want to bottle sooner than later.

          Let me know how it goes or if there’s anything I can do to help.