How Long to Bulk Age Wine

“How long to bulk age wine?” is a common discussion / area of disagreement in home winemaking. Ask 10 winemakers, you’ll get at least 11 opinions.

Note: In October 2018 I published a post regarding bulk aging, which delves more deeply into the technical aspects of bulk aging. This post is more about the “why” than the “how”.

What is bulk aging?

Bulk aging is letting the post-fermentation wine rest in containers ranging from 1 US gallon jugs to 60 gallon barrels. During this time 3 things occur:

Degassing. Fermentation produces a lot of CO2, much of which is dissolved in the wine. The wine degasses naturally over time, although kit wines introduced the concept of manual degassing, e.g., stirring the wine to expel the CO2 quickly.

Clearing. When fermentation completes, the wine has a varying amount of solids (grape pulp and yeast cells) suspended in it. The grape solids drop relatively quickly and form a sediment layer known as “gross lees”. Later the yeast cells drop and are referred to as “fine lees”. The wine is racked off the lees in several stages, producing clear wine. Note: Clearing will not complete until the wine is degassed, as the CO2 will hold some solids in suspension.

Chemical Changes. As wine ages, it goes through numerous chemical changes, which produce a (hopefully) more palatable wine. Harshness diminishes, flavors and aromas improve, etc. Note: depending on many factors (red vs white wine, tannin, acid, sugar, etc.) each wine has a finite lifespan which is normally measured in years. At some point the chemical changes will produce a decline in the quality of the wine, eventually rendering it undrinkable.

Degassing and clearing must be completed before bottling, otherwise the CO2 will push out the corks and produce a mess, and the sediment will drop in the bottle, which is aesthetically displeasing and may produce off-flavors and aromas.

As indicated above, the chemical changes will continue throughout the lifespan of the wine, hopefully producing positive changes early on, but eventually the wine will decline.

In general, fermentation typically takes 1 week, and within 3 additional weeks the gross lees has mostly dropped. At this point the wine is ready for bulk aging, where it is put in containers topped with either an airlock or vented bung. The container should be filled to within 1″ to 2″ of the stopper, depending on the shape of the container.

Degassing

Manual degassing  by stirring is a controversial topic. Kit instructions say to stir the wine up to 10 minutes, changing direction every 30 seconds. I use a drill-mounted stirring rod and stir for 2 to 3 minutes — this has proved sufficient. The wine foams up and expels significant amounts of CO2.

If I’m using a fining agent (kits typically include kieselsol & chitosan), I add it at this point and rack the wine into carboys to clear. The wine will continue to emit CO2 for a few days so a bit more headspace than normal doesn’t hurt.

Note: Folks claim that stirring introduces O2 into the wine and causes oxidation. My practical experience is that the wine is emitting so much CO2 that O2 is not a problem during stirring, and I’ve had wines last 5 to 7 years with no problems. Additionally, I’ve not seen any published papers that discuss O2 problems because of stirring.

I like manually degassing the wine as without dissolved CO2, the wine clears faster.

Bulk Aging vs. Bottle Aging

I generally get wine into the bottle as soon as is feasible. Wine is safer from contaminants in a corked bottle, and any problems are more likely to affect only 1 bottle rather than the entire batch. Also, there is solid evidence that wine ages faster in smaller quantities, so wine may be drinkable sooner when bottled sooner.

Please note that “feasible” doesn’t mean “as quickly as possible”. There are good reasons for extended bulk aging.

Certain adjuncts, such as oak products such as spirals and staves, cannot be put in a bottle and can only be used in bulk aging. Other flavorings, including spices such as cinnamon, also must be applied during bulk aging.

Bulk aging helps ensure the wine will be more consistent, from bottle-to-bottle, as a lot of the chemical changes are well underway by the time bottling occurs. I cannot recall experiencing significant differences between bottles of the same batch, but some home winemakers state they have.

Another advantage of bulk aging is the wine is much harder to drink, so it helps the home winemaker avoid drinking wines too young.

Follow is my description of how I bulk age, by wine type. Please note these time frames are not set in stone — each wine is different so I may choose to bottle sooner or later than the indicated periods.

The total duration listed in the fermentation + clearing time (typically 1 month) plus the amount of bulk aging.

Kit Wines

Kit wines are designed to bottle in 4 to 8 weeks from the start, depending on the quality of the kit. This is accomplished by manual degassing and use of fermentation fining with bentonite and post-fermentation fining with kieselsol and chitosan. The wines can be cleared and stable within 1 to 2 months.

I typically bulk age kits from 1 to 5 months. Whites and lighter reds typically age 1 to 2 months. If I add aging oak, the duration is 3 to 5 months.

Total duration: 2 to 6 months.

White Wines and Fruit Wines

I generally bulk age whites and light colored fruits for 3 months, up to 5 months if I add aging oak. Whites and light colored fruits often have a shorter lifespan and are drinkable sooner, so I get them in the bottle sooner.

Darker fruit wines are more likely to age up to 5 months, especially if I’ve added adjuncts such as oak.

Total duration: 4 to 6 months.

Red Wines

Red wines vary the most, from 3 to 12 months. I typically age basic red wines for 3 or 4 months.

If I add aging oak, the duration is often 3 to 7 months. If the wine is in a barrel, it stays there for 11 or 12 months, which is when the following year’s wine is ready to go into the barrel.

Note: My barrels are currently all “neutral”, meaning they are old enough that the wines get no oak character from the barrel itself. I add oak adjuncts (typically cubes) for oak flavoring. The barrels provide a concentrating effect as water and alcohol evaporate through the wood.

If I purchase a new barrel, the wine may remain in the barrel only 1 or 2 months, else it will extract too much oak essence and unbalance the wine.

Total duration: 4 to 13 months.

Other Factors

As I stated above, each wine is different so bulk aging is decided on a batch-by-batch basis. Especially with aging ok, the taste and aroma will affect the duration. Although I haven’t had a problem in a long time, wines that fail to clear will bulk age longer.