The refractometer is an essential tool in viticulture, particularly during the harvest. It allows winemakers to measure the sugar content of the juice, a crucial indicator of grape ripeness and the potential alcohol level of the future wines.

Operating principles of a refractometer

A refractometer uses light refraction to determine the concentration of dissolved sugars in a liquid—in this case, grape must. The sweeter the juice, the more the light is refracted and the higher the displayed value. Modern devices are compact and easy to use, offering quick and precise readings directly in the vineyard. In the past, instruments such as the gleucometer were used, which also worked by measuring sugar content to determine the precise harvest date and guide the fermentation process.

Practical tips for use

To obtain reliable results with a refractometer, several steps should be followed. Take a representative sample of berries across the plot. Gently crush them to extract the juice. Place a small drop of this juice onto the refractometer prism and close the cover plate. Look through the eyepiece to read the value indicated by the boundary line between the light and dark areas. It is advisable to take multiple readings across different parts of the plot to obtain a representative average and thereby fine-tune the decision on the optimal harvest date. Temperature can affect readings, so it is preferable to use a temperature-compensated refractometer or apply manual corrections.

At Château Cazebonne, we are committed to preserving and promoting Bordeaux's winemaking heritage, notably by replanting grape varieties that had disappeared from the region. This meticulous and passionate work is made possible thanks to the support of wine lovers who enjoy our wines. To learn more about our approach and the history of grape varieties, feel free to download our book “Bordeaux, une histoire de cépages”. Test your knowledge and discover the world of wine with our wine quizzes, and to complete your exploration of Bordeaux wines, come and discover our wines online.