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Alcohol Determination By Specific Gravity -

• This method provides an approximation of the alcohol content only.
  
  
• The method assumes that the difference in Specific Gravity before and after fermentation is due solely to the conversion of sugars before fermentation into alcohol after fermentation.
  
  
• The method relies on -
  
  
  • all the wines measured, starting with the same sugar levels
    
    
  • all the sugars being fermented, with the wine finishing dry
    
    
  • the unfermentable sugars being the same for all wines
    
    
• Keeping the above in mind -
  
  %v/v alcohol = (SG₂ - SG₁) / 0.0074
  
  
  Where -
  
  SG₁ is the initial specific gravity measurement
  
  SG₂ is the final specific gravity measurement.
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  G30. HOW TO MEASURE ALCOHOL LEVELS IN YOUR WINE To calculate Alcohol by Volume: Subtract the last reading from the initial gravity and divide the result by 0.0074. This gives the approximate alcohol content in %. Ex.: S.G. = 1.070 F.G. = 0.995 1.070 - 0.995 = 0.075 0.075 / 0.0074 = 10.15% It does not matter what the first or last reading is, both mean little alone. The difference between the two does! Usually there is also an alcohol scale marked directly on a hydrometer; subtract initial potential alcohol reading from final, and the difference is the approximate alcohol content. Using the Brix scale, 1 degree Bx = 1 g/100 ml, or 10 g/liter. When you read a Bx of say 22, divide the 22 by 2 to get 11, and add 1, for a final alcohol of 12%. It is an extremely good rule of thumb.
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  On vinometers: What they measure is sort of a balance between specific gravity and surface tension. The implicit assumption is that the alcoholic fluid has been fermented dry. fine for dry wine, but for beer or sweet wine, it won't read correctly. Dry wine has a specific gravity in the range of .998 or so, while finished homebrew is often around 1.010 (and varies a lot). {Could someone tell me the principle of how a vinometer works?} Water's structure causes it to have a very high surface tension and exhibit marked capillary action. In other words if you stick a narrow tube in the water the water is pulled up the column. The more alcohol present the more the capillary action is affected thus the height of the column changes. Add graduations based on standard solutions of water and alcohol and you have a reasonably accurate method of determining the concentration of a water alcohol solution. Problem is that wine has lots of other things that can affect capillary action and surface tension. The most prominent of these are residual sugars. That's why the instructions that come with the device probably say to only use it on dry wines (wines with minimal residual sugar). G30. HOW TO MEASURE ALCOHOL LEVELS IN YOUR WINE To calculate Alcohol by Volume: Subtract the last reading from the initial gravity and divide the result by 0.0074. This gives the approximate alcohol content in %. Ex.: S.G. = 1.070 F.G. = 0.995 1.070 - 0.995 = 0.075 0.075 / 0.0074 = 10.15% It does not matter what the first or last reading is, both mean little alone. The difference between the two does! Usually there is also an alcohol scale marked directly on a hydrometer; subtract initial potential alcohol reading from final, and the difference is the approximate alcohol content. Using the Brix scale, 1 degree Bx = 1 g/100 ml, or 10 g/liter. When you read a Bx of say 22, divide the 22 by 2 to get 11, and add 1, for a final alcohol of 12%. It is an extremely good rule of thumb. Another method is the boiling method: - take 250 ml of wine - measure specific weight and temperature - boil the wine down to 125 ml - bring up to 250 ml using boiled water - cool to the same temperature as above - measure specific weight - the difference between the two is related to the alcohol level; use the following table: diff. alcohol s/w volume % 8 5,63 9 6,40 10 7,18 11 7.98 12 8,80 14 10,51 16 12,30 18 14,10 20 16,00 22 18,00 spec. weight is in gram/litre ALCOHOL Many people ask us how do I work out my alcohol levels? The best way is to take the starting specific gravity, from the finishing specific gravity and divide this by 7.36, ie 1080 - 990 = 90 ÷ 7.36 =12.23% ABV. The other option is to acquire a Ritchie Vinometer. This is a simple device you can pour a small sample of wine into which will give an ABV reading. It's simple and quite useful as a guide. Price is under £5. VinometerThe wine tester for quality and accuracy. Uses surface tension to measure alcohol content of wines. Only accurate for dry wines. Pour sample into top of vinometer and let it flow out the bottom. The amount remaining in the vinometer will show the alcohol content. It may be useful to add a drop of food colouring to white wines to get a visible reading. SKU 50140 Purchase Classic Vinometer Put in a few drops of wine, then turn it upside down. The tiny capillary tube drains down until surface tension holds some of the wine in place. This indicates alcohol percentage, like reading an oral thermometer. Won't work after wine is sweetened. Vinometer An inaccurate piece of equipment for measuring the alcohol content of wine. The accuracy is reasonable for totally dry wines, but for sweet wines it is inaccurate, since it works on the principles of surface tension and capillary action. As a sweet wine has a high surface tension due to the residual sugar, alcohol measurement with a vinometer will give a falsely low reading. #6896 High Precision Vinometer: this triangular shaped capillary tube, for some reason, gives a far higher degree of accuracy, to .5% abv. Also included is a handy backing read-out panel which makes reading results far easier.