Barrel inspection criteria: What to Look for and Why | Practical Winery & Vineyard Magazine

May/June 2002

BY Henry Work

When you bought your first car, you drove it home, parked it in the driveway, and gave it a good once-over, even though you had inspected it several times before your purchase. After all, you wanted to know that you’d spent your money wisely because this new vehicle was going to be an important part of your life. Think of your barrels the same way — you pay good money, and they play a critical role in your winemaking life.

Since it is a product so important to your wines, you should inspect the inside of every new and used barrel you purchase. Even though the cooperage industry has made huge improvements in quality control and the general quality of barrels has probably never been higher, there are many things that can go wrong between the cooperage floor and your cellar.

Using a good barrel light inserted into the bung hole, you can check for mold and debris, while at the same time, your nose can detect any off-aromas. At several hundred dollars for each barrel and hundreds of dollars for the wine that is put into it, the labor cost of a visual and olfactory inspection to detect barrel problems is infinitesimal compared to the risk of damaged or spoiled wine.

In addition to these initial inspections, you should undertake a comprehensive physical inspection of at least 20% of the barrels you receive. Procedures of this inspection are described below.

Should you encounter any of the problems listed, contact your cooperage salesperson, distributor, or the cooperage to alert them of the situation and discuss the remedies. The feedback you provide to the cooperage greatly assists them in crafting their barrels to your needs and specifications.

Inspection ABCs
For the physical inspection, you will need a good barrel light, non-probe moisture meter, tape measure, a set of the cooperage manufacturer’s specifications, and the full attention of your eyes and nose. Begin by randomly selecting at least 20% of the barrel lot — 5% from the beginning, 10% from the middle, and 5% from the end. Mark each of them with a sample number and keep the inspection data for future reference in case of problems. Major problems in any of the areas below may require inspection of additional barrels.

This total inspection should begin with a visual examination of the barrel exterior, including the wrapping, as it may give a clue to hidden damage. Look for broken chimes, heads dented or displaced from the croze, and misaligned staves. Also look for scrapes and gouges, and especially any torn or burred hoops, which can wreak havoc on the cellar people’s hands.

Using a non-probe moisture meter (available from Tramex or Warner Electronics, among others), check to see that the wood moisture is within an acceptable range (European oaks usually contain 15% moisture +/–2%; American oaks are usually 13%, +/–2%). Too much moisture may indicate incomplete drying, resulting in a green or woody taste, and/or wood shrinkage that leads to leakage. Too little moisture can result in excessive swelling, causing the hoops to break or heads to warp.

Signs of dryness on the outside of the barrel (loose hoops, gaps between staves or headboards, and looseness in the heads) could be the result of a long, hot container ride or storage too long in a warehouse. Neither is a cause for concern, but requires a little more time and water soaking up prior to use.

Because of the excellent quality of today’s cooperage, you will rarely see the following problems, but even with the best quality control, something slips by occasionally. You need to be aware of these problems and why they are of concern.

Preventing leakage
Hairline cracks in the bilge of the staves are generally not a problem, but if they are numerous it could indicate insufficient heating of the barrel. Large cracks can be caused the same way, or from the barrel being dropped; both are a cause for concern because of the potential for leakage.

A few plugs (wedges or spiles) in the wood are normal; but several in one spot or throughout a stave or head board indicate attempts at repairing porosity or insect damage. They suggest a piece of wood with the potential for leakage. Small, tight knots, no larger than 0.5 cm in diameter, are acceptable.

Divots (hollows or gouges in the wood created during the splitting and milling processes) on either the staves or head boards are acceptable within the following parameters: they should be no deeper than one-third the wood thickness; around the chime they should not be deep enough to impact the seal of the head at the croze; and they should follow the grain pattern to indicate that they are a natural result of splitting the wood, as opposed to cut or split divots caused by dull blades when machining the wood. In excess, these last types of divots may indicate poor jointing, leading to leakage. There should also be no sapwood in the joints, as it will eventually leak.

Tale of the tape
Carefully inspect the metal hoops; watch for tears or burrs as noted above. Look also for stretched or sheared rivets, which indicate that the hoops have been put on too tight and may burst if the barrel expands. Using the manufacturer’s specifications, measure the hoop placement. Hoops more than 1 cm off, different from barrel end to barrel end, or different from barrel to barrel could indicate variation in capacities, with the potential to frustrate stacking and or racking from barrel to barrel.

While your tape measure is out, measure the barrel dimensions and compare to the manufacturer’s specs — all dimensions should be within 2%. In addition to problems caused by different capacities, large discrepancies in the length or bilge diameter could also indicate barrels made at different times or at different locations — which could be a problem if variations in capacity become an issue.

The bung hole is of prime importance, since it is the gateway not only for your wine, but for microorganisms as well. The bung hole should arrive covered, either by a bung, whether the flat wooden shipping type or silicone which should be intact, or by plastic wrapping. Plastic wrap around the barrel will seal the bung hole during shipping. The hole should be the size you have specified, not what the cooperage wants to give you. It should be centered on the bung stave, round, and evenly and thoroughly cauterized to seal the bung well and prevent wicking around the bung.

The bung stave should be wide enough to support a hole without cracking, usually 10 cm (four inches) or more. Look carefully in the hole to the inside of the stave; there should be no great cavities or cracks to capture and hold wine. Since this is a prime evaporation area, it is a location extremely susceptible to spoilage.

Going inside
You are now ready to inspect the inside of the barrel. Be cautious of excess sulfur exposure as you place your face near the bung hole. Take small, shallow breaths through your nose as you slowly edge closer. If you do find a strong smell of sulfur, allow the barrel to air out before proceeding. Barrels made a month or two prior to delivery at the winery should have little sulfur smell. A large dose of sulfur could indicate an attempt to hide a problem, so air the barrel out and look closely.

Cooperages generally use sulfur as a precaution against mold growth when water has been used while testing barrels for leaks. Barrels shipped over the ocean are most susceptible to mold problems due to condensation within the shipping container. While most cooperages are shipping barrels that have been sulfur gassed, some may still use wicks, or used barrels, shipped from some wineries, may have been wicked. If wicks have been used, look for sulfur drips which could cause hydrogen sulfide upon introduction of a wine.

The point of this inspection is to look for mold and to smell for off-odors due to mold or other bacterial spoilage, but you are also checking to see that the barrel is clean and free of sawdust, strips of flagging hanging into the barrel, wood chips, and trash. I experienced the latter once, I am ashamed to say, when a customer returned a small piece of sandpaper, that had been found in the barrel.

The inside of the barrel should be dry. Look for mold, particularly near the croze where the heads meet the staves. This is the most likely spot to contain some standing water from the testing process, or from the flour paste that is used in the croze, which is an excellent medium for mold if the area was too moist.

The barrel aroma should be clean, fresh, oaky, and/or toasty. Other than sulfur, there should be no chemical odors. Be aware of possible smells from such things as preservatives or paints, which can be introduced during transit in a shipping container, especially if a bung is missing.

A new or newly refurbished shipping container may have a high residual paint aroma or vapors from the preservative applied to the floorboards. There is some evidence that links these preservatives to trichloranisol (TCA) taint in the wood of the barrel. Should any of these aromas be detected, contact the cooperage, as well as a wine laboratory, to check for TCA or other contamination.

The toast color should be within your specifications, and should be fairly uniform throughout the body of the barrel, and from barrel to barrel. The ends of the staves normally have little toast color, especially in light or medium toasted barrels. It is also normal to have some variation stave to stave. Color that is “too uniform” indicates some manipulation with the toasting fire, such as a cover being used which can produce an undesirable smoky taste.

Unfortunately, color is only an approximate indicator of time on the fire, but a rich, uniform, non-smoky color without excess blisters is normally the only indicator a winemaker has of sufficient time on the bending and toasting fires. If toasted heads have been requested, they should also be of uniform color and of equal shade on both heads.

There is much debate over blisters, especially regarding whether they have a tendency to induce wine spoilage. Some winemakers believe that blisters become a collection point for wine, which can then spoil when the barrel is empty. But others assume that given the porosity of the wood and in combination with good cleaning procedures, blisters pose no more potential for spoilage than do any other nooks and crannies of a barrel.

Regardless of the correct answers to that continuing debate, while some blisters are normal, excessive blistering or very large blisters (2 to 3 cm deep and 4 to 5 cm long) indicate rapid heating of the wood, or the use of oak with an excessive moisture level. Both of these are signs of shortcuts taken during the coopering process, and are cause for real concern for the eventual taste of the wine.

Summary
The three most serious problems for new barrels are: 1) indicators that the barrel will leak, 2) mold or off-aromas inside the barrel, and 3) too much or too little toast on the inside. In the first case, ask the cooperage to repair the barrel; in the second and third cases, reject it.

For the past 10 years, Henry Work has been general manager of Canton Cooperage in Kentucky. He and his staff have transformed Canton from a bourbon barrel producer to a premium American oak wine barrel cooperage. Before working at Canton, Work was a partner in Barrel Builders in Napa Valley. There he learned the art of coopering without hitting his thumb too many times.