Uluru, Northern Territory, Australia

NuKorc Technical Information


The dimensions below are for closures designed for insertion into CETIE finish bottle bores with a diameter of 18.0mm - 19.0mm, controlled at 3.0mm down and 20.0mm down. For closures to suit other bottle bores, please contact us.

37mm Closure 40mm Closure
Length (mm) 37 40
Diameter (mm): 22 22
Weight (gm): 6.3 6.8
Density (gm/cc): 0.45 0.45
Peak Extraction Force (kg): 20 - 40 20 - 40
Coating FDA - EU Compliant, food-grade silicone

The dimensions below are for bottle bores 17.0mm-18.0mm diameter controlled at 3.0mm down and 20.0mm down. For other bottle bores please contact us.

37mm Closure 40mm Closure
Length (mm) -0,+0.4 -0,+0.4
Diameter (mm): 20.6 - 21.4 20.6 - 21.4
Weight (gm): 5.5 - 6.1 5.9 - 6.4
Density (gm/cc): 0.44 ± 0.03 0.44 ± 0.03
Peak Extraction Force (kg): 20 - 40 20 - 40
Coating FDA - EU Compliant, food-grade silicone

Oxygen Transmission

The NuKorc closure has been tested by an independent laboratory using a MOCON test instrument. Full length samples were inserted into wine bottles and tested until a steady state was reached. According to the laboratory, the NuKorc closure was found to have "extremely high barrier properties".

  37mm Closure 40mm Closure
Oxygen transmission rate
(cc/pKg*day*atm O2)
0.012 0.012

* Oxygen transmission rate testing was conducted at 23°C with the test gas at 40% relative humidity (RH). Pure oxygen was used as the test gas. Air at 21% oxygen was used as the test gas.


Functional Comparison of Natural Cork and NuKorc: Samples of NuKorc and a commercial Ref. 2 natural wine cork were inserted into standard CETIE bore bottles using a standard four jaw Bertolaso corking machine. Extraction forces and off cork screw measurements were taken after twelve months. Results are expressed below:

NuKorc Natural Cork Ref. 2
Low Average High Low Average High
Peak Extraction Force (kg) 27.0 33.0 36.0 23.7 33.4 37.3
Cork Screw Removal (Nm) 0.45 0.45 0.65 0.43 0.54 0.71

Recovery Properties Following Compression

In order to understand the recovery properties of NuKorc compared to natural cork bark, samples of each closure type were passed through a four jaw Bertalaso corking head set at 16.0 mm. Measurements were then taken at intervals to establish how quickly each closure recovered to its starting dimensions.

NuKorc Natural Cork Ref. 3
% recovery % recovery
Initial diameter (mm) 22.1 100.0 24.1 100.0
5 seconds after compression (mm) 21.9 99.0 23.1 95.8
30 seconds after compression (mm) 22.0 99.5 23.3 96.6
60 seconds after compression (mm) 22.1 99.7 23.4 97.0
10 minutes after compression (mm) 22.1 100 23.4 97.0

Recovery Properties of Closures Inserted into CETIE Bottles

NuKorc began research into the recovery properties of its closures in 1996. The pressure exerted by the closure against the bottleneck is critical to long-term performance. NuKorc demonstrates excellent sealing pressure, even after a lengthy time in the bottle. This can be seen from bottles of wine sealed with NuKorc closures over a period of time*. Once extracted, the rate of expansion of the closure can be measured, as in the testing above. Closures inserted into bottles four years ago are still recovering at the same rate as our currently produced closures.

*Insertion of closure with a Bertolaso four jaw corking machine with a headspace pressure of -20KPA. Test results are available

Bottling Protocol

Corking Machine

  • A four segment sliding jaw assembly is recommended (hand corkers are not recommended).
  • NuKorc compression diameter no less than 16.0mm for bottles with 18.5mm neck.
  • Corker to be maintained to manufacturer's specification.
  • Central alignment of cork plunger to jaws.
  • Corker jaws to be thoroughly cleaned daily and at changeover.
  • Natural cork dust should be vacuum cleaned from all parts of the line.
  • Check 10th NuKorc to pass through each set of jaws for creasing, cutting or crushing.
  • The use of heated corker jaws is not recommended.
  • Please leave bottles standing upright for 24 hours following NuKorc insertion.

Ullage Space - Head Space - Air Space

  • Should not be less than 15mm at 20°C (if wine is less than 20°C fill height should be adjusted to compensate for wine expansion at ambient temperature).


Adjust the vacuum pump to give -10 to -25 kPa internal pressure after closure insertion. Do not exceed atmospheric pressure.

Post Bottling

Use a pressure gauge attached to a fine hollow needle to measure headspace pressure in the bottle five minutes after closure insertion. The pressure should be between -10 and -25 kPa.

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