Wood Barrel Cask Care
By: Thomas J. Payette, Winemaking Consultant
Premium oak barrels can be one of the best places to store certain wines and some of the worst.? This is mostly subject to what style of wine one wants to produce, how one cares for the full barrels and how one stores barrels that are empty.? The best rule of thumb for many is: A full barrel is a “happy” or “safe” barrel.
? Water will be mentioned multiple times in this article.? It is assumed the water is always chlorine free water.? Do not use chlorinated water on barrels or in wineries in general.
When?
? Every winemaker has his own way of taking care of his barrels.? In essence, there is no right way to take care of a barrel, just many wrong ways.? Neglecting the timely applications of just a few simple processes may result in spoilage bacteria becoming established in the porous grain of the wood that will be a cumbersome battle for the future.? If we are timely and diligent in our barrel care, we save ourselves time, work and dollars keeping sound oak barrels for up to a decade or more.?
Golden Rule of Thumb: Visit each barrel once a month.? Full or empty.
New Barrels
? Most winemakers have several diverse ways to prepare their barrels for their first fill.? This can range from no treatment (not recommended), quick rinse, head soaking to full fill.? Visually inspect and smell every barrel before filling just to know what your hard-earned juice/wine is about to go into and extract.? Always remember it is better to find a leaky barrel with water.? Not wine or juice!
No Treatment: Some winemakers will simply receive the barrel and fill the barrel up with juice or wine.? However, there are few cases where the barrel will leak, so most winemakers at larger premium wineries generally do not recommend this. (Not recommended)
Quick Rinse: Acceptable in some cases if the barrel is allowed to soak up the water to swell beyond the leaking point if that may be an issue.? The author still finds risk with this process unless potentially using a form of pressure test to know that the barrel will not leak. (Not recommended)
Head Swell: There are winemakers that fill their barrels with about 10-15 gallons of water and allow them to sit on one head for 12-24 hours and then roll them over to allow the opposite head to have contact with the water.? This, in my opinion, is still better than the above solutions because of the time needed for the wood to swell is taken properly before placing juice or wine in the barrel. (still not recommended)
Full Fill: Either using cold or hot (120 degrees F) water to completely fill a barrel (roughly) 12-24 hours prior to needing the barrel.? This time can be shortened if all looks well and leaks are not discovered.? Cold water can be used also. (Recommended)
? Do keep in mind not to extend the time longer since the water can turn smelly and certain slims/films may develop [from the water].? If more time is needed freshen the water or make a solution of citric acid water (pH to near 3.5 or lower) and SO2 (near 60-70 PPM).? This solution will allow longer contact time with the wood if that is desired.
? I, depending on the cooperage used, prefer to fill barrels with fresh water at 120 F, bung solid and allow to cool overnight before emptying the water the next day, allowing draining completely for one hour (bung hole facing downward) then righting, doing another visual and smell check, then filling.
Freshly Emptied Barrels
? Barrels that have been freshly emptied of wine are often overlooked too long.? A barrel that is empty will start to dry reasonably rapidly so we must take the bull by the horns, even though we may be tired or distracted, to manage these empty barrels as soon as possible.? As with any clean up, if one can get to the dirt before it dries the clean up goes much easier.? Try to at least give the barrels a good solid rinse as soon after emptying as possible.?
? A good solid rinse may be a reasonably high-pressure rinse to loosen and rinse the sediment from the barrel.? Then start any other cleaning regimens from then on or perhaps if re-filling one may be fully prepared for this action at this time.
? If further cleaning is needed this can also be a time to start a more serious high pressure washing regimen, ozone or any other sought after method to address a specific need.
? Be sure to take the time to clean the bung area of the barrel both inside and out.? The bung area can be a place for solids to dry and for large numbers of bacteria to proliferate, if uncared for.
Storing of Empty Barrels
? Many readers are perhaps scanning this article for answers just to this issue.? Wide-ranging experiences have winemakers storing empty barrels in various fashions.? The author prefers to rinse a freshly emptied barrel as described above, allow the barrel to drain overnight bung downward and then re-right the barrel – with bung facing skyward.?
Liquid Sulfur Dioxide: Fresh pure liquid sulfur dioxide can be the best choice, in my opinion, yet care must be taken when using this liquid gas.? Please follow all MSDS and handling instructions.? Another common-sense helpful task is to only do this outdoors, upwind from the barrels and away from others.? The author typically will meter 10 grams of pure liquid sulfur dioxide per 60-gallon (225 liter) barrel for the initial dose and then re-dose at 5 grams every month thereafter.? If the author has ever been in doubt what may be too much pure sulfur dioxide, he always leans toward more in the empty barrel scenario because he has not seen any literature suggesting the negatives of slightly higher use.? This is not to say to go higher than recommended or to become excessive.? Please be careful here.
Wicks and Disks: This is another form of introducing sulfur dioxide into the barrel.? Most sulfur wicks contain roughly 5 grams of sulfur dioxide in them and yield this upon burning.? This is another terrific way to take care of your barrels when empty.? Please remember to re-burn a wick/disc in the barrel every month.? Visit each barrel, full or empty, once a month.
Storage Conditions: Do your absolute best to store barrels, full or empty, in the best conditions possible.? One should strive to store barrels full or empty at or near 50 degrees F, out of direct sunlight, avoiding excessive temperature swings and in a mold-free environment.
Dixie cup, Styrofoam, or Bung?
? There are winemakers who allow barrels to be stored unbunged after treatment with sulfur dioxide.? These winemakers are few.? Others use different methods of sealing the barrels to keep the risk of insects and small animals out of the barrels.? The most popular methods are:
Dixie? Cups:? These fit nicely in most 50 mm bung whole openings and do an excellent job at sealing the barrel just enough to keep the gas inside the barrel.? They do tend to pop out as some like to store the empty barrel bung down while empty. (Not recommended)
Styrofoam? Cups: These are like the Dixie? cup above with essentially the same function. (Not recommended)
Bungs:? The author prefers this seal to the barrel to best keep the gas in.? It is also recommended to wrap these bungs in Seran? wrap to protect the bung silicone from the harsh sulfur dioxide environment.? This is functional and the clear wrapping is a wonderful way to identify empty wine barrels in your cellar from a distance visually.? (Recommended)
? I have little experience with glass bungs or other forms of barrel closures for this purpose. These may need further review in your own cellar.
Types of Rinse
Water: All types of rinse generally use water.? Please keep in mind this should be Chlorine free and have enough pressure to rinse the back and top of the vessel in question.? This can be difficult with larger barrels such as puncheons.
High Pressure: Nice to have but not essential with overall good cellar practices.? This will aid in tartrate removal and it has much more logical mechanical pressure removal than just typical water pressure in a winery.
Ozone: Increasingly popular but this process must be used with caution and in well-ventilated areas.? With best cellar practices these machines should not be needed but they are a great tool to fight back when bad spoilage bacteria become troublesome.
Hot Water vs. Cold
? I feel it best to rinse barrels with hot water after emptying.? 150–170-degree Fahrenheit water is preferred for this step and the rinse is generally about 1- 2 minutes to complete the task of mostly clear water coming from the barrel. Please note hot water would not be used with ozone.
Monthly Management
? Whether full or empty, each barrel needs monthly attention.? Try to store full and empty barrels at or as near 50 degrees F when possible.
When Full: One will need to taste and check the free Sulfur Dioxide and pHs of these wines monthly at a minimum. After this check, additions can be made to the wines in the barrel and then they can be topped.? Topping is one of the keys to keeping a barrel safe from bacteria spoilage.? The wines used must be of sound chemistry and microbe free to make this a successful statement. The topping wine must be “clean.”? I will often use a dry wine from a tank that has been tightly filtered and nearing bottling to be certain the bacteria load is greatly reduced, or absent, from that vessel.
When Empty: Once again, we will need to visit each barrel monthly.? In all cases the barrel will have been rinsed and sulfured prior.? We should return to these same barrels and retreat with Sulfur Dioxide by gas or wick (see above) to ensure the barrels’ integrity will continue to be sound.
Where
? Most work with empty barrels will happen outside on a crush pad or strung out in caves and warehouses.? When possible, try to have more than ample space and ventilated air moving through the workspace if using liquid Sulfur dioxide or wicks/discs.?? When possible, the author prefers to unstack the barrels, remove the bungs, look inside the barrel with a flashlight and then smell the barrels at each visit.
? If the barrels must stay in place, one can easily work with them also but some of the more critical reviews of sight and smell become more cumbersome.
Rain
? At certain times at certain winery locations the author likes to use Mother Nature.? It is common to plan a day’s barrel work around the weather.? If the weather forecast is for rain the author finds advantages, with uncovered crush pad areas, to do a days barrel work, rinse the interior and then allow the barrels to remain on racks, bung down, in the rain to get a nice soaking cleaning on the exterior as well.? This can also apply in conjunction to the swelling procedure above but with barrels full of water and bung upward.? Please try this experiment first on a small batch of barrels since wood discoloration may take place and not be visually to one’s liking.
? Always clean the bung opening area and when needed one can cauterize / burn that area again.? This process may be needed about every 5 years or so at the maximum and a special tool is needed for this process.
Tartrate Removal
? Tartrate removal can be a nuisance for those that focus on it.? In general, it should not be a huge issue.? Do note that winemakers may care to cold stabilize their wines before placing them in barrel for this reason.? Most do not, however.? Also note that when one looks inside the barrel one will see more tartrates because they typically “fall out” and go to the bottom.? In the case of sur lie wines in the barrel the yeast layer does a wonderful job of protecting the bottom of the barrel from tartrate adhesion to the wood.?
? A high-pressure rinse may remove these tartrates effectively.? A hot water rinse may help them “flake off” and dissolve more readily.
? There are winemakers who use a high pH (warm water helps here) soaked by a light citric acid soak.? This can be highly effective in tartrate removal.? Make sure the soda ash, the high pH solute, and citric acid, the low pH solute, dissolve completely before adding any one of them to a barrel.
? Some more European trained winemakers will insert a stainless-steel chain and have the less stipend “summer help” roll the barrels with the chain inside to knock the tartrates free – then rinse and Sulfur.? Be sure to devise a way to retrieve the chain from the barrel.?
? In most cases, however, the tartrate removal is not a huge focus for many winemakers due to practical applications.
Tools Needed
? The many tools for barrel care may be purchased at winery supply stores, cooperage houses and other specialty suppliers specific to these types of products.? Research your needs and then contact these companies to see what they offer.? In general, only a good barrel rinser, good to great water pressure (chlorine free) is needed and the way to introduce the SO2 – wick or gas.
Glass Head Barrels: A great tool to be able to see inside the barrel when performing certain tasks from burning sulfur wicks, filling, rinsing, lees stirring etc.? Watching fermentation and malo-lactic with these glass head barrels can be fascinating beyond the other features.? Every cellar should have at least one of these glass head barrels to better know what is happening inside their barrels with certain specific functions.?
Humidity
? Humidity is undoubtedly a factor when dealing with barrels.? The author prefers a less humid cellar to make sure the vacuum needed inside the barrel is fully established on barrels with wine in them.? If barrels are kept full and production practices to store few barrels empty for any length of time are employed, this can be the best way to use barrels to their fullest and best capacity.? There is some “angel’s breath” evaporation loss but that is a part of the process.? If a barrel is stored for less than three months empty most will have few to no issues with reswelling.
Spicing it Up!
? There are winemakers who prefer to cold stabilize their wines before placing them in barrels to prevent tartrate from building up in the barrels. (referenced above) This can be effective, but most winemakers do not do this in large practice.
? Burning a sulfur wick in a barrel (5-6 grams) does two things.? It puts sulfur dioxide into the barrel as well as displaces oxygen with carbon dioxide.? This practice may lend toward mimicking by the winemaker using a carbon dioxide flush on their barrels then using pure liquid sulfur dioxide.? There are large wineries who use liquid Sulfur Dioxide, and this may apply to their needs best.? These large wineries also could make dry ice on site, and this could be used as the Carbon Dioxide source.? This may be the way of the future to help combat spoilage bacteria growth in barrels.? This may well be the future established standard for proper barrel care.
Wrapping it up
? Tackling the barrel care issue is a trying one but an easy one.? There is only one way to do it right.? The way it works for your cellar.? There are multiple off branches and combinations of what has been described above.? Please take from this article anything you think may help with your current process and refine, for the better, what will work best for your winery and wines.? These are examples of must-do processes but most recommendations have some variation.
? In all, be diligent and respectful of the barrels in your cellar and they will provide many years of service to you, your cellar, and your wines.
Other Helpful Tips / Observations
??? Alcohol is less dense than water or juice.? It is not all too uncommon to fill a barrel with water to validate the barrel will not leak, only to find a barrel may develop a leak later.? These leaks can typically be fixed on site of the winery with little effort.
??? Do not fill a barrel with wine you know to be bacterially unsound.? This will only start the spread, further, of unwanted bacteria.
??? Smelling the barrel is one of the best ways to acknowledge its condition and readiness to potentially help or harm your wines in the cellar.
??? Whether full or empty, each barrel normally requires a form of monthly maintenance.
??? Topping and resulfuring on time is critical.?
??? Lower storage temperatures (50 degrees F) can be an especially useful tool and one more winemakers should try to strive to use.
??? Resist the temptation to store barrels outside.? There are wood-boring insects that may take fancy to this easy target leaving the winemaker with leaky barrels.? Small periods of time outside may be acceptable.
? Generally American oaks tend to need reswelling more than European woods.? I have also noticed American oak may develop more non-bacterial ethyl acetate type aromas when stored empty due to a chemical reaction of the wood, moisture, and Sulfur dioxide.? This is generally not a bacterially generated ethyl acetate aroma if sound procedures are followed and not a concern – just an observation winemakers may notice in their cellars and to be aware.
? Uprights and ovals beyond the 600-liter capacity are beyond the scope of this article and care should be taken to establish contact with appropriate sources to secure proper methods of working with these wood vessels.
References:?
Verbal discussion with Jacques Boissenot, Chris Johnson, and Jacques Recht.
Many thanks to Mark Heinemann (deceased) and all the Demptos Cooperage team for their help.