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 youd 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.
For the physical inspection, you will need a good barrel light, non-probe
moisture meter, tape measure, a set of the cooperage manufacturers
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 peoples 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
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 todays 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.
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
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 manufacturers 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
While your tape measure is out, measure the barrel dimensions and
compare to the manufacturers 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.
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.
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,
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.