A few months back we had a brief discussion on the rate of decrease in wine volume in barrels (ullage). At that time I decided to measure the topping up of my two barrels. One is a 60 liter French Limousin barrel containing a Cab Sauv/Merlot blend (Barrel #1) and the other is a 55 liter squat (burgundy styled) Hungarian barrel containing Chardonnay (Barrel #2).
Days from Total Wine Average Daily last filling Loss (mls) Loss (mls)
Barrel #1 12 375 31.3 Barrel #2 12 100 8.3
Barrel #1 9 100 11.1 Barrel #2 9 175 19.4
Barrel #1 21 375 17.9 Barrel #2 21 375 17.9
Barrel #1 13 150 11.5 Barrel #2 13 125 9.6
Barrel #1 17 150 8.8 Barrel #2 17 350 20.6
Barrel #1 11 125 11.4 Barrel #2 11 150 13.6
Barrel #1 20 250 12.5 Barrel #2 20 175 8.8
Since all measurements were taken on the same it is easy to directly compare the loss and it was surprising that there is quite a variation between the two barrels, in one case more than three times the volume. Also, the fact that both barrels behaved quite inconsistently ie neither required consistently more than the other. I will admit that my readings were taken from estimates in the wine I used from top-up bottles but I feel the accuracy was likely within 100 ml as I always use bottles or half bottles to top up. The highest rate of loss (barrel #1, first reading could have been an error) but there were also several higher readings between 17.9 and 20.6 ml/day.
I know there are several factors that influence ullage apart from the size, tightness of the barrel and other construction factors and probably the type of oak. I expect these other factors are primarily temperature and humidity and maybe even barometric pressure.
My primary learning is that I thought I was topping up more frequently than I was especially since I was doing the test I probably topped up even more frequently than usual. In the future I plan to record the date of topping up so that I can monitor my frequency a little better, expecially in the summer.
Any comments would be appreciated.
Cheers,
Glen Duff