The hydrometer is one of the most critical pieces of equipment for wine making. It measures the sugar content in the "must" - the pressed grape due prior to fermentation - allowing the wine maker to predict and if necessary influence the level of alcohol in the final product.
When I originally used the internet to look up information sources on the hydrometer, I found that many different scales of measurement are used. On top of this, descriptions of wine-making in English often use Imperial measurements - and obviously in Hungary we don't! So although the basic principle of the hydrometer is very simple, it took a bit more reading than I expected to get a full understanding of its usage.
When I originally used the internet to look up information sources on the hydrometer, I found that many different scales of measurement are used. On top of this, descriptions of wine-making in English often use Imperial measurements - and obviously in Hungary we don't! So although the basic principle of the hydrometer is very simple, it took a bit more reading than I expected to get a full understanding of its usage.
This most excellent page gave me quite useful information on how to use the hydrometer, although since this page is based on imperial measurements and specific gravity, neither of which our hydrometer uses, I had to do some mental adjustments to take it all in. Luckily there is a conversion table.
Our hydrometer is shown below, after we pressed the white grapes and then the red. It shows a sugar level of about 18 for the white must, and 19 or so for the red must. An ideal level for the fermentation process is around 20 to 21. The reason grapes are left as long as possible on the vine before picking is to naturally maximize the sugar level. This summer was very sunny so most people picked the grapes a little earlier than last year.
Now a bit of technical stuff...
The Hydrometer works on the Archimedes principle that a solid suspended in a fluid will be buoyed up by a force equal to the weight of the fluid displaced. Thus, the lower the density of the substance, the further the hydrometer will sink.
Hydrometers are used in fields other than wine-making, with varying measurement scales. In wine-making alone, there are at least 3 scales used. In English-language information sources, "specific gravity" is most commonly used. Our hydrometer - apparently the common type in Hungary at least in amateur wine-making - is based on the Brix scale. Degrees Brix (°Bx) is a measurement of the dissolved sugar-to-water mass ratio of a liquid. A 20°Bx solution is 20%, with 20 grams of sugar per 100 grams of liquid. Or, to put it another way, a measurement of 20°Bx means 20 grams of sucrose and 80 grams of water in 100 grams of must.
The Hydrometer works on the Archimedes principle that a solid suspended in a fluid will be buoyed up by a force equal to the weight of the fluid displaced. Thus, the lower the density of the substance, the further the hydrometer will sink.
Hydrometers are used in fields other than wine-making, with varying measurement scales. In wine-making alone, there are at least 3 scales used. In English-language information sources, "specific gravity" is most commonly used. Our hydrometer - apparently the common type in Hungary at least in amateur wine-making - is based on the Brix scale. Degrees Brix (°Bx) is a measurement of the dissolved sugar-to-water mass ratio of a liquid. A 20°Bx solution is 20%, with 20 grams of sugar per 100 grams of liquid. Or, to put it another way, a measurement of 20°Bx means 20 grams of sucrose and 80 grams of water in 100 grams of must.
Applying this in practice, the measurement we collected from the white must was 18 degrees. We added sugar to bring it up to an optimal level of 20-21 degrees for making this white wine. In the above-mentioned page about the hydrometer - which uses Specific Gravity rather than Brix scale - 18 degrees brix corresponds to 1.075sg, and 21.4 degrees brix corresponds to 1.090sg. That source says that fermentation ideally starts around the 1.090sg level.
A factor to consider is "potential alcohol", meaning the potential alcohol level of the finished wine after the yeasts convert all the sugar to alcohol. 18 degrees brix corresponds to a potential alcohol level of 10.2%, 21.4 degrees brix corresponds to 12.2% alcohol. This is a desirable level for a white wine. For contrast, a dessert wine would target something more like 16%.
Since in both cases our sugar levels were good, but too low, sugar (just regular table sugar) was added to bring it up to the ideal level of about 20 to 21 for the fermentation process.
One final thing. In the pictures of the hydrometer above, you can see "20°" written on it. To confuse matters further this is nothing to do with the sugar level but rather the optimal temperature of the must when the hydrometer is used. That is, the hydrometer is calibrated based on a must temperature of 20° - so if the temperature is significantly different, then one needs to make manual calculations to determine the actual sugar level. It's unlikely that our must was 20° when we measured the sugar levels, but no-one seemed to care. In any case, the amount of added sugar was also based on quick mental calculations - so for an amateur wine it seems not to matter too much. I guess the pros take it more seriously!
A factor to consider is "potential alcohol", meaning the potential alcohol level of the finished wine after the yeasts convert all the sugar to alcohol. 18 degrees brix corresponds to a potential alcohol level of 10.2%, 21.4 degrees brix corresponds to 12.2% alcohol. This is a desirable level for a white wine. For contrast, a dessert wine would target something more like 16%.
Since in both cases our sugar levels were good, but too low, sugar (just regular table sugar) was added to bring it up to the ideal level of about 20 to 21 for the fermentation process.
One final thing. In the pictures of the hydrometer above, you can see "20°" written on it. To confuse matters further this is nothing to do with the sugar level but rather the optimal temperature of the must when the hydrometer is used. That is, the hydrometer is calibrated based on a must temperature of 20° - so if the temperature is significantly different, then one needs to make manual calculations to determine the actual sugar level. It's unlikely that our must was 20° when we measured the sugar levels, but no-one seemed to care. In any case, the amount of added sugar was also based on quick mental calculations - so for an amateur wine it seems not to matter too much. I guess the pros take it more seriously!
