About Us News & Events Contact Us Site Map
Rakuto Kasai Ltd
About Us
Home  >  Wine Technology  >  Natural and Synthetic Corks > Handling of corks

Handling of corks

Handling/Processing Advice


Storage of Corks

Natural corks should be stored in a well-aired odor free area at about 18-20 degrees C.

  • If stored below 15 degrees C, natural corks can become hard and brittle resulting in imperfect sealing.
  • If stored above 25 degrees C, natural corks can become too soft.

This could result in the corks coming out of the bottleneck.

Storage / Utilization of Corks before bottling

Natural corks should be stored at least 24 hours before being used at 18/20 degrees C.
The corks should be used within 6 months from date of delivery.



Use only bottles whose neck has an inside diameter that corresponds
to the DIN proposed standard dated March 31, 1988:
Inside diameter at bottle rim: 18.3 mm +/- 0.4 mm
Inside diameter at 40- 47 mm down: 20 mm +/-1 mm


Corking Jaws

The corking jaws should be regularly examined for damage before and during use. Damaged jaws may cause creases and other irregularities to the cork; leakers and increased cork dust may result. When fully compressed, jaws should not close to more than 16 mm.



In order to avoid cork dust, the following parts of the corker should be carefully examined before use:

  •  Hopper, or any moving parts of the hopper: to determine if any sharp edges are detected.
  • Cork shoot or tube: to determine if any sharp edges are detected.
  • Corking jaws: (see above #3)
  • Heated jaws should not exceed 80 degrees C
  • Star wheel should be appropriate for the bottle diameter

The centering cone and plunger should be examined for exact placement above the bottle resulting in an optimum seating of the cork in the bottleneck.


Filling Height

The filling height depends on the type of bottle, the cork length and the temperature of the wine at bottling: For a standard claret bottle with a 44 mm long cork at 20 degrees C, there should be 55 mm of space between the lip of the bottle and the wine itself; this would be about 11 mm head space. With a cooler wine, the filling height is correspondingly lower; with a warmer one, correspondingly higher. (Please refer to our bottling fill level chart.)


Internal Pressure

The internal pressure of the bottle should be examined at regular intervals. For vacuum corkers, once per hour is advised. The needed resting time after corking depends on the internal bottle pressure.


Bottles neck up
or laid down

About three hours after corking, the natural cork regains 95 % of its original diameter; after 24 hours 99 % of its original diameter. (Depending on the cork’s moisture, these times may vary slightly). Ideally, to avoid leakers due to positive head pressure in the bottleneck, bottles should remain upright for 24 hours. In the case of pressure reducing devices such as CO2 injection or vacuum corkers, maintaining bottles upright for 5 minutes is adequate.


Storage and
Transport of
Bottled Wines

Great variations in temperature during the storage and transport of finished wine should be avoided. The changes in volume causes by temperature variations may result in corks moving up or down the bottleneck resulting in leakers.