Tank & Barrel Management
We cellar the wine in stainless steel tanks, oak barrels and glass or plastic (polyethene) containers. We use:
- Steel tanks and steel barrels for mixing and transferring wine: They are easy to clean and maintain and they last forever.
- Oak and steel barrels for maturing wine: Oak barrels, up to 3-4 years old, add desirable flavours and tannins to the wine. After 4 years, they are called neutral. The advantage of oak barrels, in addition to adding flavours, is that they breathe: they allow very slow oxidation from air that enters through the wood staves. As air enters, liquids evaporate through the wood. Consequently, the barrels need to be topped up every 1-2 months. A similar effect can be achieved in steel tanks by inserting oak staves or chips and by injecting oxygen at an extremely slow and controlled rate (micro-oxidation).
- Speciality steel tanks and glass containers for keeping odd lots and top-up wine. They are easy to clean and come in various sizes (glass carboys) or have adjustable volume (steel tanks with variable tops or pressurised inert gas covers).
We currently don’t use plastic containers (they are easy to clean and very versatile) or micro-oxidation systems (too expensive).
Economics of oak barrels
For large wineries, stainless steel tanks are hands-down the most economical solution because they come in enormous sizes and are easy to clean and maintain. Only commercial wineries which can charge over $40 retail per bottle tend to use new oak barrels. A new 60-gallon oak barrels costs between $600 (for American and East European varieties) and $1200 (for French varieties) and they add desirable flavours to the wine for 3-4 years; after that, they are called neutral and trade for $150-$300 in the secondary market. Neutral barrels, when properly maintained can last for over a decade. New 60-gallon stainless steel barrels cost $500-700 and last forever. So, using new French oak barrels for every vintage would cost around $20/gallon or $3.50/bottle. We use a mixture of mostly French, and some American oak barrels 50% new and 50% neutral. Our average cost for using French barrels is below $2/bottle or less than the combined subsequent cost of the glass bottle, cork and label.
Choosing Oak Barrels
At trade shows, barrel makers have the fanciest booths and spend the most on brand marketing. That is because the characteristics of barrels are hard to measure and much depends on individual taste and image. On top of the difficulty to quantify qualities, research studies indicate that characteristics of the same type of barrels from the same manufacturer vary widely.
We buy maximum two new barrels a year. Consequently, we have no opportunity to test a wide range. So we decided, somewhat arbitrarily, to concentrate on buying our barrels from Radoux, one of the large, well regarded French “Tonneliers”. We tried a couple of barrels from Seguin Moreau but found them to impart too intense flavours. American oak, as compared to French oak, imparts different flavours and has a slightly higher oxygen transfer rate (see the page on Elevage). As these comments indicate, we conservatively end up buying from an established large supplier – not much analysis or research involved here.
Choosing Stainless Steel Tanks, Barrels & Kegs
Stainless steel containers are made to individual specifications by speciality manufacturers or bought from catalogues according to standard sizes and specifications. We are using 4 types of stainless steel containers:
Mixing and settling tanks can hold the contents of multiple barrels and are used to mix different barrels or hold young wine for a short period to settle out suspended particles. We prevent the wine from coming in contact with oxygen by a floating blanket of a “heavier than air” inert gas; we use Argon or CO2. These tanks have large openings on top and the side for easy cleaning. We use a round stationary 200-gallon mixing tank (made to order by Santa Rosa Stainless Steel) and another square 200-gallon mixing tank (ordered from Metalcraft ) which can be raised with a hydraulic forklift.
Storage & transfer barrels can hold 30 or 60 gallons of wine and are used to hold wine while a barrel is cleaned, or for ageing without exposure to oak and oxygen (unless oak chips or staves are used, or oxygen is infused with micro-ox equipment). We bought our 30 & 60-gallon steel transfer barrels from Transtore.
Variable top tanks are designed to hold variable amounts of wine. Their top floats on the surface of the wine in the container and is sealed with an inflatable gasket to prevent exposure to air. We use them for small batch fermentations and, in the past, to hold odd amounts of young wine set aside for topping-up barrels. We bought our 100 & 200-liter variable-top tanks from Fermentation Solutions.
Pressurized kegs are designed to hold variable amounts of wine (usually 5-15 gallons) under slight pressure of an inert gas (e.g. Argon). We use them to hold young wine set aside for topping up barrels. We bought our two 15 gallon kegs and associated piping from GW Kent.
All of our tanks and barrels are on dollies so they can be moved around easily and they are designed so they can be lifted (by hoists or forklift) to move the contents by gravity instead of pumps.
Carboys are glass containers that usually come in 4, 5, 6 & 7-gallon sizes. We use them to hold odd lots of excess wines. They always need to be filled to the top to prevent the contents to be exposed to air.
Barrels need proper maintenance. They must be adequately humidified to tighten up before first use, they must be cleaned regularly of sediments and wine spoilage organisms, and they must be stored properly when not full of wine.
Cleaning is about removing sediments settling at the bottom of the barrel and about killing wine spoilage microorganisms (bacteria and fungi, mostly hiding in crevices and near the top of the barrel). There are for primary methods of cleaning:
- Water: spraying the inside of barrels with cold or warm/hot water is the most common method of washing out crud and sediments, but it is not very effective in removing spoilage microorganisms
- Sulfur Dioxide: Barrels can be washed out with a solution of SO2 or KMBS (potassium metabisulfite which when dissolved in water creates molecular SO2, a dissolved gas) or they can be gassed by burning a pure elemental sulfur wick. Sulfur is cheap and pretty effective against wine spoilage microorganisms, but it is toxic when inhaled.
- Steam: Barrels can be steamed to wash out and kill microorganisms. Steam is very effective to clean, but it is expensive to apply (equipment), and it only works for a short time while hot – as soon as the steam cools down, new microorganisms can resettle
- Ozone: Barrels can be washed out with water containing Ozone molecules O3 which are very useful in killing all kinds of harmful microorganisms (bacteria, fungi and biofilms). This requires an ozone generator and diffuser. The disadvantages of Ozone are: it deactivates fairly quickly, it is pretty harsh on anything containing rubber (gaskets, seals etc.) and should only be used in well-ventilated areas as it can be toxic when inhaled in quantities above 0.2 milligram ozone per cubic meter of air.
What we do when
Here is our current barrel maintenance practice:
- Initialization: before we use new barrels we fill them with filtered warm water (stripped of chlorine and contaminants found in regular drinking water) and let the stave soak up and tighten. This takes a few days. Then they are rinsed out with the barrel washer (see below) and immediately filled with new wine.
- Regular cleaning between uses, at racking: We wash barrels with a specially built washing apparatus. It first removes residues with a sprayer applying warm water until the water runs clear. Then we spray out the barrel with cold ozonated water, and we clean around the bung-hole with KMBS spray. To conserve water, a basin under the barrel catches the outflow, and a pump circulates the water back through a prayer inside the barrel. For the ozone treatment, a bubbler fed by the ozone generator is placed inside the barrel.
- Storing used barrels: if a barrel is not refilled with wine after washing, we burn a sulfur pill inside and close it, so the trapped SO2 prevents the growth of new microorganisms. The burning pill is held in the centre of the barrel in a small stainless steel basket suspended from the bunghole.The burning is repeated every 4-6 months if barrel storage is extended. Before the barrel is reused, it is washed inside with the barrel washer (see above) and outside with a steam power washer used for general cleaning of the steel tanks, destemmer and the press.
The pictures show the barrel washer, the steam pressure washer and sulfur pill holder.
The database has a table dedicated to describing the tanks and barrels. Each new vessel is entered into the database with the following layout. The key items are a unique name and dimensions to calculate the usable volume.
The following screenshot shows the current set of vessels: