What is Sur Lie Aging?

Sur lie aging in a barrel with a glass end.

Notice the thin layer of fine lees on the bottom of the barrel.

Sur lie aging is the process of allowing a finished wine to continue to sit on the lees in order to extract flavors. Recently we explored the fact that there are two different types of lees. There are the grape lees (coming from the fruit) and the yeast lees (you guessed it, from the yeast). Each of these can be used in sur lie aging and each will produce different results.

Aging wine on the grape lees is something to be undertaken with extreme care as this lees can easily spoil a wine if not done properly. When done correctly though it can lead to a wonderfully complex wine.

Yeast lees on the other hand is the more common lees to perform sur lie aging with. As the yeast decomposes it can impart nut, bread, and yeast flavors to a wine. Different yeast cells can contribute different flavors too so you’re not guaranteed to get the same thing from all yeast strains. The remainder of this article pertains to aging on the fine lees only.

How does Sur Lie Aging Work?

During sur lie the lees cells break down (i.e. decompose) into simpler compounds. This releases sugars and proteins that interact with the wine chemistry. There are also flavor and aroma compounds that get released.

As the proteins are released they bind with tannins in the wine. This is good for a white wine as you don’t want tannins in a white. However, for a red wine this can be problematic as it is the tannins that go a long way in determining the aging potential of the wine.

For this reason red wines are usually not aged this way while white wines often are. The deciding factor depends upon the intentions of the wine maker.

If the lees are left undisturbed in the bottom of your aging vessel for too long they can start to form some nasty sulfur flavors and aromas. To keep this from happening you need to stir the lees regularly, a process called battonage.

Stirring the lees keeps hydrogen sulfide from forming as quickly and ensures that your wine gets maximum exposure to the cells and the compounds they’re decomposing into.

Things to Watch Out For

As you proceed through the sur lie process be sure to pay special attention to the flavor profiles of your wine. You can over do this and end up with off flavors.

If at any point you experience sulfur like flavors like rotten eggs, rack off the lees immediately. The sooner you take action the better your chances are of being able to deal with these off flavors. Taken too far and your wine won’t be drinkable.

When to Age on The Lees

Preparation for sur lie aging begins as fermentation is wrapping up. The lees should be stirred up every two to three days for the last bits of fermentation.

Once fermentation has ended continue to stir the lees once or twice each week for a period of six weeks or so. After that stir it up monthly.

Some wine makers prefer to perform malolactic fermentation after sur lie aging, however, there are no hard and fast rules when it comes to MLF and sur lie aging combined. It’s something that has to be experimented with.

How Long To Age It

Most resources recommend wine makers sur lie age for eight to ten months.The time spent on the lees, however, can vary greatly from a matter of weeks to upwards of 12 to 24 months. By in large you have to determine the sur lie aging time as you go based on how your wine tastes. Again, always be on the look out for any hints of sulfur flavors or aromas.

Some resources state that you can sur lie age wine on grape lees for years at a time if done correctly. Blackwood Canyon Vintners claim to have wine still on the lees after fourteen years (http://www.blackwoodwine.com/educate/surlies.html). This is, however, the exception from what I’ve found.

The Benefits of Sur Lie Aging

Beyond picking up additional flavors and aromas there are a couple other benefits to sur lie aging. First, the binding of proteins to tannins serves to remove tannins and shape the mouthfeel of the wine.

Second, the layers of lees in the bottom of your aging vessel absorb oxygen thus protecting it as it serves up new character. So not only are you adding complexity, removing unwanted tannins, and shaping your wine you’re also setting it up for maximum protection against oxidation.


Sur lie aging can be a really beneficial process to take your wine through if done carefully and with a lot of attention being paid to how the taste is progressing. As you taste your wine be aware that there is a limit to the positive effects of this process.

For your first try at sur lie aging consider racking a gallon or even just a bottle or so of wine, with the lees, and take it too far on purpose. Not that we want to ruin any of your wine but it would be helpful to understand what flavors and aromas develop as the process goes beyond the beneficial stages. This way you’ll have a better understanding of what to look for regarding off flavors and aromas.

Photography by: Arnaud 25

  • Brian Angell

    I am a bit confused. You say: “The lees should be stirred up every two to three days for the last bits of fermentation.” During fermentation there are gross lees there, right? At what point do you rack off gross lees and continue processing on fine lees. How long does it take for gross lees to settle for racking – you shouldn’t stir them if you want them settled, right?

    • Hi Brian, you’re quite right to be confused, that was not made clear in the article. The methods described above pertain to aging on the fine lees as this is the more common form of sur lie aging.

      A wine should be racked off the gross lees after five to seven days. You can push this further but it’s a delicate process and you need to be ready to rack at the first sign of off flavors.

      You are correct, in that you don’t really want to stir up the gross lees, especially if you plan on racking at the five to seven day mark as they likely won’t be settled out enough to get a clean racking.

      Gross lees can settle out at different rates depending on the fruit and carbon dioxide production. I can imagine a situation with a vigorous yeast producing a lot of carbon dioxide and keeping the lees pretty well churned up.

      In summary, I would sit on the gross lees for five to seven days, rack off of it, then proceed with the battonage schedule of stiring the fine lees.

      Thank you for the question! I went back and edited the article to make it more clear what I’m talking about.

      Cheers! -Matt