Ullage Calculations -
Leaking wine bottles are often erroneously blamed on poorly performing closures, but unless the closure has serious physical defects, the reason for leakage is usually due to improper bottling practices and excess bottle pressure after bottling.
The throat diameter of a standard, American 750ml bottle will vary slightly in the ullage area. On average, however, it is fair to say that the ullage with a 49mm cork and a 64mm fill height will average 4.8 ml. in volume. For a 45mm cork the correct volume would be 6.5 ml.
If the winery bottles at legal fill heights and with adequate vacuum to assure that there will be no more than 2 pounds relative pressure in the bottle at 68°F, it is very unlikely that the customer will ever complain about leaking corks.
- Bottle wine at 68ºF and fill to the level designated by the bottle manufacturer and confirmed by the winery.
- Adjust the fill level to compensate for temperature differences. A good rule of thumb is to adjust the fill level by 0.55mm for every degree Fahrenheit above or below 68ºF.
- Adjust vacuum levels to compensate for temperature differences. This method seems less reliable than adjusting fill levels because it places so much responsibility on the performance of bottling equipment. Internal bottle pressure needs to be equivalent to less than 2psi (relative) at 68ºF.
Fill Chart by Temperature*
Wine
Temperature |
Fill Level
from Top |
Ullage*
|
|
45mm Cork
|
49mm Cork
|
||
72ºF
|
61.3mm
|
15.3mm
|
11.3mm
|
71ºF
|
61.8mm
|
15.8mm
|
11.8mm
|
70ºF
|
62.4mm
|
16.4mm
|
12.4mm
|
69ºF
|
62.9mm
|
16.9mm
|
12.9mm
|
68ºF
|
63.5mm
|
17.5mm
|
13.5mm
|
67ºF
|
64.1mm
|
18.1mm
|
14.1mm
|
66ºF
|
64.6mm
|
18.6mm
|
14.6mm
|
65ºF
|
65.2mm
|
19.2mm
|
15.2mm
|
64ºF
|
65.7mm
|
19.7mm
|
15.7mm
|
63ºF
|
66.3mm
|
20.3mm
|
16.3mm
|
62ºF
|
66.8mm
|
20.8mm
|
16.8mm
|
61ºF
|
67.4mm
|
21.4mm
|
17.4mm
|
60ºF
|
67.9mm
|
21.9mm
|
17.9mm
|
59ºF
|
68.5mm
|
22.5mm
|
18.5mm
|
58ºF
|
69.0mm
|
23.0mm
|
19.0mm
|
57ºF
|
69.6mm
|
23.6mm
|
19.6mm
|
*Assumes cork recessed 1mm below bottle top |
Bottle Pressure by Temperature*
Wine
Temperature |
Fill Level
from Top |
Max Pressure*
|
|
45mm Cork
|
49mm Cork
|
||
72ºF
|
63.5mm
|
4.6 psi
|
5.4 psi
|
71ºF
|
63.5mm
|
3.9 psi
|
4.5 psi
|
70ºF
|
63.5mm
|
3.2 psi
|
3.6 psi
|
69ºF
|
63.5mm
|
2.6 psi
|
2.8 psi
|
68ºF
|
63.5mm
|
2.0 psi
|
2.0 psi
|
67ºF
|
63.5mm
|
1.5 psi
|
1.3 psi
|
66ºF
|
63.5mm
|
1.0 psi
|
0.7 psi
|
65ºF
|
63.5mm
|
0.5 psi
|
0 psi
|
64ºF
|
63.5mm
|
0 psi
|
-0.5 psi
|
63ºF
|
63.5mm
|
-0.4 psi
|
-1.0 psi
|
62ºF
|
63.5mm
|
-0.8 psi
|
-1.5 psi
|
61ºF
|
63.5mm
|
-1.2 psi
|
-1.9 psi
|
60ºF
|
63.5mm
|
-1.6 psi
|
-2.3 psi
|
59ºF
|
63.5mm
|
-1.9 psi
|
-2.7 psi
|
58ºF
|
63.5mm
|
-2.2 psi
|
-3.1 psi
|
57ºF
|
63.5mm
|
-2.6 psi
|
-3.4 psi
|
*Assumes relative pressure - base of 16.2 psi |
Calculations are based on specific dimensions for Bottle Type:
750ml Claret Premier (Cal Glass / Owens Brockway) - other bottles may differ.
Management Suggestions
One way of dealing with ullage calculations is for bottling managers to chart out target fill heights and internal bottle pressures by bottle type in advance of bottling. Though this will not eliminate their responsibility for a "legal fill'', it will provide an excellent guideline for good bottling.
It is also critical that wineries keep good ongoing records during the bottling day. At a minimum, the following protocols should be observed.
- Freshly corked wines from each corker head should be checked at a minimum every hour for internal pressure [suggested interval is every 30 min].
- Quality control should not rely on the temperature gauge at the filler. A thermometer should be dropped into one bottle ex-filler every half hour.
- If bottling line Q.C. tests bottles that are out of spec for fill or vacuum at a specific temperature, the associated product should be quarantined, [preferably] flipped upright and checked out. Only when the problem is resolved, should cases be returned to regular inventory.
- Q.C. should always check out the readings on cork probe gauges against one another in the morning and again at noon.
- These gauges should also be used to check the functioning of the corker gauge [not vise versa].
- If there is a problem with the vacuum on one or more of the corker heads, the line should be stopped until it is cleared. This should not be done "on the fly".
Maintaining Legal Volume
Legal fill levels are an important requirement. We recommend the following process:
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Large Format Bottles
The ullage tables in this bulletin are designed for 750ml bottles, and calculations need to be adjusted for different bottle sizes. In particular, large format bottles can exhibit tremendous expansion under high temperatures. For bottling conducted at 68ºF, the CQC suggests allowing 8ml of ullage for every Liter of wine. For a 3L bottle—that is 24ml. This target would be adjusted for different temperatures. To determine the volume, place a mark (A) where the bottom of the cork is expected. Fill the bottle with water. Subtract 18ml and mark the fill height (B). |
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