Cork Quality Council  Recommended Corking Practices for Wineries

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I. CORKER JAW TYPE  The 4 segment sliding roller or iris jaw type cork compression system is recommended. Roller or iris type jaws tend to cause wrinkles in the cork which can cause leaking.  II. CORKER MAINTENANCE  Corking machines are maintained to manufacturers recommended standards at all times.  Smooth action in compression stage.  No nicks or other damage to the jaw segments.  Good alignment and seal of bottle neck in centering bell.  Properly centered plunger.  Daily cleaning and sanitation of cork handling surfaces; i.e. hopper, feed tube, orienter, and jaws.  A 24mm cork should not be compressed to less than 16mm.  III. CORK HANDLING AND STORAGE  Do not open plastic cork bags until immediately before loading corks into the loading corking machine. No bags containing corks should be left open for any reason.  Corks recovered from the corking machine after the bottling is completed should be returned to the plastic bag or another closable container "dosed" with sulfur dioxide gas (vapor) and sealed tightly. CQC companies can provide this service.  Corks should be stored in a cool dry location, not in a bottling room, barrel storage area, or chemical storage area. The temperature should be 55 to 70 degrees Fahrenheit and the humidity 50 to 70 percent.  IV. MOISTURE CONTENT  New shipments of cork, as well as corks which have been stored for extended periods of time, should be checked for moisture content before use. Corks below 5% average moisture level should be discarded or returned to the supplier for rehydration and sterile packaging.  Corks with an average moisture content of over 8% should be regarded with suspicion as such moisture level could support mold growth.  V. INTERNAL BOTTLE PRESSURE  Wine temperature should be between 60-70 degrees F. If lower temperatures are used then the fill point should be adjusted down to compensate for expansion in the bottle when room temperature is reached. Be sure to maintain legal fill volume.  If the fill pint is too high, less vacuum can be achieved.  The vacuum system should be well controlled and maintained. Gauges which continuously display vacuum status at the corking head and request (each 1/2 hour) on line QC of corked bottles (pierce test) are highly recommended.    Bottles should remain upright for 24 hours after corking. It is recommended that the above elements be combined to produce a net effect of no more than 3 psi internal bottle pressure at 68 degrees