The alcohol content expressed as alcohol by volume (ABV) is a crucial metric in the world of spirits, indicating the alcoholic strength of a liquid. Expressed as a percentage, ABV shows the proportion of alcohol in a drink. For example, a spirit with 40% ABV contains 40% alcohol and 60% water or other components. This standard measurement is how companies let you know just how potent their beverages are.
What is an Alcometer?
An alcometer is a specialised tool used to measure the alcohol content in a spirit. Due to the difference in density between alcohol and water, the higher the alcohol concentration, the deeper the alcometer sinks. This device is indispensable for anyone making their own spirits, as it provides accurate readings essential for quality control and safety.
Why You Need an Alcometer
Alcometers are not just for hobbyists; they're vital for ensuring the correct dilution and filtering of spirits. When preparing a distillate, you’ll often need to dilute it with water. This step is crucial, especially before filtering or ageing, as different processes require different ABV levels. For filtering, aim for an ABV between 40-50%, following your specific filter's guidelines.
When it comes to ageing spirits like whisky, dark rum, and brandy, the optimal range is typically between 50-70% ABV. However, personal preference can dictate a lower ABV. Using an alcometer ensures that you achieve the desired strength, enhancing both flavour and safety.
For a comprehensive guide on diluting and filtering, check out our article Dilution & Filtering: Mastering the Art of Spirit Refinement.
How to Use an Alcometer Effectively
To use an alcometer, you'll need a test jar for accurate readings. Begin by thoroughly cleaning both the alcometer and the test jar with warm water, then dry them well. Hold the alcometer by the thin part above the scale and fill the test jar to about three-quarters full with the spirit.
Place the alcometer in the jar and give it a gentle spin to release any gas bubbles that may cling to it, which could skew the reading. The ABV is read at the point where the surface of the liquid meets the scale on the alcometer, specifically at the bottom of the meniscus.
For more detailed information on taking cuts during your spirit run, refer to our article Spirited Separation: How Distillers Make Cuts.
Calculating Final ABV When Using Flavourings
When adding flavourings, the calculation of the final ABV becomes crucial. Here's a simple formula to follow:
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Determine the Volume of Alcohol Required: Subtract the volumes of flavouring and water from the total final beverage volume.
Example for Still Spirits Top Shelf Select Liqueur Rhubarb and Ginger Gin:
Final beverage volume: 1000 ml
Flavouring volume: 330 ml
Water volume: 170 ml
Calculation:
Volume of alcohol required = 1000 ml - 330 ml - 170 ml = 500 ml
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Calculate the Final ABV: Use the formula:
% ABV of made-up liqueur = % ABV of alcohol called for in recipe X (volume of alcohol in recipe / final finished beverage volume)
Example: If the alcohol used is 40% ABV, the final ABV for the made-up liqueur would be:
% ABV = 40% X (500 ml / 1000 ml) = 20% ABV
Key Considerations
When using additives like flavourings or liquid glucose, be aware that they can alter the readings of your alcometer. Always measure your ABV before adding these components. Additionally, the temperature can impact accuracy; alcometers are calibrated for use at 20°C. If your sample's temperature deviates more than 3°C from this, your readings may be off.
For continuous ABV monitoring during distillation, consider using a parrot head. This device allows for real-time measurement without needing to take samples, making it easier to make precise cuts.
Lastly, for your safety and enjoyment, it's best to avoid consuming spirits with an alcohol content exceeding 65% ABV.
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