Current Baume'

Testing Baume' 

Each week, after veraison, I test the grapes to determine their ripeness.  Picking will start once the grapes reach 13 Baume. This should translate into wine with a little more than 13% alcohol. The table below shows the progressive ripening of the grapes, expected yield and picking date. The grapes are have gone backwards with the recent heavy rains, if we can string together 3-4 days of good weather they should return to expectations.. The readings below are those of the most advanced block of grapes, other blocks will ripen at different rates, so fruit should be available over 3 to 4 weeks. The graph shows the variation between samples taken 12 rows apart throughout the vineyard.

 The graph below suggests we could be on track for a late February start. The logarithmic projections are essentially straight lines, but when compared with the 2009 data, you can see that the ripening process is not always linear.

The Process

1.  I collect the
grape samples.  I ride down the rows of vines stopping every 30 metres or so, and collecting 3 grapes from 3 different bunches (east side, west side, shade, sun), from 3 different canes and from 3 different parts of the bunch (top, middle, bottom). I put these in a jar to take back the the shed (laboratory sounds too grand) for testing.

2.  I crush the grapes
to allow the juice to mix as a single sample.

3.  I use a refractometer to read the sugar levels. Sugar levels are measured using either the Brix scale (which gives % sugar) or the Baume' scale which gives the approximate alcohol in the made wine. My refractometer measures Brix, which I translate into Baume'.

The refactometer works by putting a sample of the grape juice on the slide, closing the cover and looking through the eyepiece. Light bends (travels slower) through dense matter. The more sugar in the juice, the more the light bends. The refractometer focusses the light onto a scale for reading.