Racking is a pretty simple procedure: Moving wine from one vessel to another. However, depending on when you rack and how you do it, you can help ensure a clean and happy wine, as well as fine-tune a style. Racking can be done to expose a wine to oxygen, during or after fermentation, both with different aims. It can be done to soften and open a wine, and to reduce or remove reduction. It can be done to remove some or all of the lees. It’s a versatile tool, though if timed improperly or done too much, can damage a wine, so strategy — both with timing and execution — is important.
The most gentle way to rack wine, employed by most home winemakers, and the way without a pump, is by gravity. Siphoning wine with a tube from one vessel, placed higher up, into another, placed below. For wine to flow, the “in” end of the tube must be higher up than the “out” end, the second they are level, or reversed heights, flow will cease or reverse.
The bigger the height difference between each end, the faster the wine will flow. Also, the wider the inner diameter of tube used, the faster the racking will go. Remember also that A = πr2 so that doubling the tubing’s diameter doesn’t simply double the rate of wine flowing through the tubing, rather flow rate rises exponentially based on the tubing’s radius. Also, choose food-grade plastic hose for your racking tube. To stop flow temporarily, you can crimp the hose toward the “out” end of the hose with your fist (there are simple plastic crimp devices found at most homebrew shops that can be used as well), releasing when you wish for flow to begin again. This is a great way to stop flow between bottles while you are bottling. There are also various manual bottle filler rods that close when they are lifted off the bottom of the bottle.
Racking can be done to expose a wine to oxygen, during or after fermentation, both with different aims.
In the receiving vessel, you can minimize oxygen exposure by putting the “out” end of the hose below the surface of the wine (once there is enough wine in the vessel to do so) while discharging the wine. Alternatively, you can encourage oxygen exposure by “splash racking,” which is splashing the wine against the side of the vessel as it discharges. The difference in oxygen pick up by the wine between these two techniques is huge, 12 fold or more (Jackson, 555). These two techniques each have their own places in winemaking, which will be explained below.
For most white wines, the goal is to keep rackings to a minimum, keeping oxygen exposure to a minimum. For the most part, you always want to rack with the “out” end of the hose submerged to minimize oxygenation, as white wines cannot absorb oxygen without oxidizing as reds can.
After fermentation has finished, most choose to rack off the gross lees. Although aging on the gross lees can add an interesting character, it is risky — they’re heavier and more prone to reduction, as well as potentially harboring more spoilage bacteria — and this unique character is not to everyone’s taste. If you want to keep your fine lees in the wine for aging, rack a day or two after fermentation has totally stopped (for the gross lees to settle), then rack. If you want to minimize the amount of lees you take with you after fermentation, wait about 5 days post-fermentation, as long as the wine smells clean. A rule with racking is that gross lees, being heavier than fine lees, settles about 24 hours post agitation (from fermentation ending or bâtonnage), whereas fine lees slowly settles over 5 or so days. You can also rack soon after fermentation, and again after the lees have settled, but with whites, it’s best to minimize the racking’s oxygen exposure.
If fining later in the wine’s life, rack off the lees (if you have kept them), adding in your fining agent little by little as the wine fills the receiving vessel (to evenly distribute the fining agent). I recommend cold stabilizing at this time as well, as precipitated tartrates will settle on top of the spent fining agent, compacting it more. A more compact lees means less wine loss when racking off of the fining agent. Of course the timing of when you fine will vary depending on your stylistic and practical goals. Once racked off the fining agent, the wine is ready for filtering and/or bottling.
If you’ve had to carry out multiple rackings with a white wine, or are concerned that it has seen too much oxygen in its life, you can always purge the receiving vessel with inert gas (CO2 and argon are preferred over nitrogen here, as they are heavier than oxygen). You could even sparge the vessel you are racking from as headspace opens up or apply a slight amount of pressure on the headspace (1–2 psi) if you’re especially concerned.
Reds offer a bit more flexibility, as they can happily absorb oxygen, especially early on in life, and as they don’t need to be fined. There are really only two times a red wine needs be racked, but more may be beneficial for a particular wine. The first is after pressing when most winemakers let a red settle for a day or two to let the gross lees settle before racking into the aging vessel. The second is racking off of any lees/sediment before bottling.
Many winemakers will rack off the lees (if they choose to at all) once malolactic fermentation (MLF) has finished, sometime in the winter following harvest. Lees both feed ML bacteria (lowering the need for nutrient addition) and help maintain a reductive environment (they can absorb a lot of oxygen), which ML bacteria prefer. ML bacteria create their own lees, as well.
However, in absorbing oxygen in this early stage of a red wine’s life (the first 6 or so months), they inhibit oxidative polymerization of tannins and color (the latter of which lees also adsorb), which may not be ideal for wine softness and longevity. So their removal soon after fermentation has ceased may be advisable, especially in lower color varieties, tannic/potentially astringent varieties, or wines made being to age as long as possible. Letting the wine settle longer after fermentation/pressing will likely take care of removing the vast majority of lees.
Although lees can have the benefits we’re familiar with (mouthfeel, lees aromatics, coating/softening tannins), another potential danger of them is that they harbor spoilage microbiota, which could potentially harm a wine. So many winemakers, especially natural winemakers whose wine may be more biologically diverse, may want to remove the lees for that reason as well.
Splash Racking vs Submerged Hose
What’s better? This depends on timing, variety, and style.
For whites, you almost always want to submerge the hose to avoid oxygen exposure. If the wine gets reduced, you can splash a bit at your own risk — but only while the wine still has a lot of CO2 left in it from fermentation.
The first 6 or so months of a red’s life, as tannins and color polymerize, it is able to absorb (some would argue eager to absorb) much more oxygen than later in its life — the older the wine gets, the less oxygen it can handle without oxidation problems arising. A good, oxidative racking early in a wine’s life may benefit polymerization, open a wine up, and aid development. Depending on the variety you might want to splash rack early in a red wine’s life and submerge the hose later.
A good, oxidative racking early in a wine’s life may benefit polymerization, open a wine up, and aid development.
Some red varieties are more prone to oxidation — think less structured varieties like Pinot Noir and Grenache — and in this case, especially in lighter wines from this class of grapes, you may always want to submerge the hose. Structured grapes like Syrah and Cabernet Sauvignon may need to have a good splash racking (or a few) to ward off reductive (hydrogen sulfide) odors.
Finally, stylistically: If you want an open, softer wine, more oxidative racking (splashing) would guide the wine in that direction. If you want a more reductive, angular, lean wine, more reductive (submerged hose) racking may be for you — although after pressing or early in life, all but the lightest red wines can usually use a good splash racking.
Racking and Reduction
What to do when reduction (hydrogen sulfide or H2S) rears its (potentially) ugly head? Don’t reach for your copper immediately! Copper sulfate is probably unnecessary, and may be subtly damaging to a wine’s structure and longevity, obviously damaging to aromatics, not to mention not being great for the human digestive tract at higher levels. Especially if you catch a wine getting reduced early on, a good splash racking will often blow off that stink.
Before discussing further, keep in mind that a little H2S may not be a bad thing, especially if your fermentation was clean. It can add complexity and will slowly dissipate with time in the bottle. In other words, there is a time and place for reduction, so if you smell a touch of reductive funk, it’s not necessary to do anything — only if you don’t like it, or it seems to be increasing and you are concerned. Some winemakers actively seek reduction, employing practices in the vineyard (late season sulfur spraying) and cellar (reductive winemaking) to create reduction.
If you do want to keep your wine reduction-free, early detection is key as H2S can turn into mono-mercaptans, and later di-mercaptans (the two mercaptans require copper sulfate for their removal). How do you know when a wine has crossed the line from H2S to mercaptans? Take a bit of wine and get a lot of air into it, let it sit for a few hours or overnight, then compare it to another glass of the wine just out of the vessel—if the aerated glass has lost its stink, you should be good to go with a splash racking. The same goes for reductive ferments, getting a lot of air into them usually solves the issue
Another option is the “penny trick.” Take two small glasses of the stinky wine in question, and toss a penny into one glass (a normal, copper coated penny is fine). Swirl it around for a bit and compare the two glasses by smell. If the glass with the penny quickly cleans up, you either have H2S or mono-mercaptans. If the stink remains you have di-mercaptans. Although oxygen exposure won’t fix the mono-mercaptans, a splash racking will likely clean up what H2S still remains and could lead to further mercaptans. With a low level of mercaptans, it may not be worth going the copper sulfate route unless they bother you. If the stink remains after the penny trick, you have di-mercaptans, which require a more complex approach of ascorbic acid and then copper sulfate to fix.
Tips and Tricks
Pumps can make life much easier during racking. But be sure to get a pump that is self-priming and food-grade. If you’re racking via gravity, there are a few concepts that you need to keep in mind. Gravity racking requires the receiving vessel be placed low, which often means on the floor. To start suction, it may seem like you have to squat and get your face near the ground to do this, and this is a bit of a pain. A back-sparing approach is to suck wine to near the end of the hose, and crimp or cover the out hole with your thumb. Then, lower the out end of the hose into your receiving vessel (and below the level of the in end of the hose) and release. Flow should start, and you haven’t had to contort yourself onto the ground to achieve this. Purchasing an auto siphon is another easy to get racking started, but just note that the seals on this can wear out so replacement every few years may be recommended. As mentioned earlier, applying a very light pressure of an inert gas like CO2 can also be used to start the racking process.
If racking off the lees, even being careful not to disturb them when getting your vessels into place, some lees will be resuspended into the wine. If you stage your racking the night before, this will give the disturbed lees time to settle back down, so you will not risk sucking them up when racking.
This would also be a good time to tilt your vessel by placing a small object under one end (be sure to do so in a way that leaves the vessel stable). Having the vessel at an angle will cause the wine to pool to one side once the wine level gets low, and you will be able to rack more clean wine off the lees, and lose less wine, than if the vessel was laying flat.
Racking is one of the basic parts of winemaking, but one with diverse uses and approaches. While watching liquid move from one tank to another is rarely very entertaining, doing so in a way which helps you achieve your style goals can make it a lot more satisfying.
Jackson, Ron. Wine Science: Principles and applications. Academic Press (555).