Image of the Month: January 2014
Celebrating the New Year – Champagne Cork
Actual Champagne Cork
Grayscale Axial slice of Champagne Cork
Virtual 3D model of Champagne Cork in
CTVox
Colored Slice of Champagne Cork
As a celebration of the New Year many of us opened a bottle of champagne. The unmistakable
popping of the cork starts the New Year with a bang! So we decided to place the cork into a
Micro-CT scanner and investigate what makes this stopper so great.
Cork comes from the Cork Oak, Quercus suber and is found near the western Mediterranean
Sea. There are various countries that produce cork such as Spain, Italy, Morocco and others but
the largest producer is Portugal with 55 percent of the market. Total production of cork is
approximately 3,075,000 tons worldwide of which 70% is used for bottle stoppers. That is a lot
of cork especially since its density is only 0.12 to 0.25 g/cm3.
The cork comes from the outer bark called the cork cambium. Removing this layer from the tree
does not harm it but takes time to regrow. The first stripping of the bark happens when the tree
is 15 to 30 years old with a trunk diameter of 70 centimeters. Initial stripping is known as virgin
bark and is not useful for cork stoppers because of its irregularity. After 9 years, a second
stripping is done, again this still is not useable. The third and any subsequent strippings are
useable for cork stoppers because of its uniform texture. The best cork is when the tree is
between 50 to 100 years old although in the total lifetime of the tree (160-180 years) there will
be about 15 strippings (once every 9 years). Click on the link below to see a short video of how
cork is harvested from the tree.
http://www.youtube.com/watch?v=ztr-RP0XYd8
This cork cambium consists of many cells that are 0.03mm in diameter with 15-42 million of
these cells per cubic centimeter of cork tissue. These cells are filled with air giving cork its
useful characteristics for champagne stoppers such as compressibility, elasticity, and
impermeability to liquids. As the cork is squeezed into a glass bottle, the air inside the cells
compresses, exerting pressure to create the seal. Over time, the gases in the cells diffuses out,
losing its elasticity. This happens 10 to 15 years after storage.
Now, you are probably wondering how cork is made. One way is to punch the cork directly out
of dried cork slabs. The other is to ground the cork board that was left after punching and create
an agglomerate cork that is bound with glue or food grade silicone. Champagne corks are
actually a combination of both. The upper portion of the cork is an agglomerate and the lower
portion consists of glued cork discs. Champagne corks are unique in that they must be made to
withstand pressure of 6 times atmosphere. In order to achieve this, the diameter is set to 31mm
compared to 24mm for regular wine corks. These diameters are then compressed into a wine
bottle with a diameter of about 18mm.
Taking a look at our scanned champagne cork you can notice the agglomerate section and the
cork disc sections (Figure 1).
Agglomerate Section
Disc Section
Figure 1. Agglomerate and disc sections of the scanned Champagne Cork
Looking at an axial slice of the agglomerate you will notice the light areas around the edges of
the agglomerate sections where glue is used to hold the cork together (Figure 2). The axial slice
of the disc section is quite different (Figure 3). The disc section, which is punched out, is more
uniform with the only defects being the pores or higher density cork. A coronal view of the cork
shows clearly the agglomerate and disc sections (Figure 4).
Glued Edges
Figure 2. Axial slice of glued cork agglomerate
Figure 3. Axial slice of disc section of cork
Agglomerate Section
Disc Section with lines
showing glued areas
between discs
Figure 4. Coronal slice of cork showing both glued agglomerate and disc slice sections
The champagne cork was scanned twice, both with our SkyScan 1173 µ-CT. One scan was
done at 46 µm pixel size at 40kV and no filter. The second scan was performed at 14 µm size in
order to see the glue in the agglomerate more clearly. The rotation step for agglomerate clarity
was reduced to 0.2 degrees. The images were reconstructed in NRecon, axial slices viewed in
DataViewer, and the 3D model and movie was created in CTVox. Below is the video for the
cork.
System
SkyScan 1173 High Energy Micro-CT
Voltage
40kV
Current
200µA
Pixel Sizes
46.32µm, 13.89µm
Rotation Steps
0.4, 0.2
Scan Times:
00:32:25, 03:44:45
Software
NRecon, DataViewer, and CTVox
Location
Micro Photonics Imaging Laboratory, Allentown, PA
Courtesy of
Brandon Walters, Laboratory Technician, Micro Photonics
Date
1/7/2014
References
http://www.nytimes.com/2012/12/23/magazine/who-made-that-champagne-cork.html?_r=0
http://www.extension.iastate.edu/NR/rdonlyres/173729E4-C734-486A-AD16778678B3E1CF/73964/WineCorks.pdf
http://www.wwf.org.uk/filelibrary/pdf/corkscrewed.pdf