A hydrometer is a measuring tool generally made from a heavy glass tube and used to analyze the density of a liquid. The idea behind the hydrometer is that suspending a solid object in a liquid will cause it to float as much as the weight of the fluid displaced. This means the tool will sink less in a less dense liquid. Brewers make use of the hydrometer to analyze the progress of their beers or other fermented beverages, as the density of the liquid decreases as the yeast converts sugar into alcohol.
Steps
Method 1 of 2: Taking a Reading
Step 1. Review the hydrometer temperature calibration
Hydrometers analyze the density of a liquid, but liquids expand and contract with changes in temperature. To get an accurate answer, you need to analyze liquids at the temperature for which the instrument is designed. This temperature should be listed on the label or package instructions.
- Most water meters for artisanal production are calibrated between 59 and 60 °C and most laboratory water meters are calibrated at 20 °C.
- Hydrometers can lose accuracy over time. If you're using an older tool, it might be helpful to try it out first.
Step 2. Measure the temperature of the liquid
If it differs by more than a degree or two from the intended temperature of the hydrometer, record the result. The measurement will be divergent, but it will be possible to correct it based on the temperature spreadsheet at the end of the article.
When testing craft beer, it is important not to contaminate it with an unsterilized thermometer. Use an adhesive strip thermometer that sticks to the side of the container or measure a sample rather than the entire batch
Step 3. Pour a sample into a clean container
Choose a clear pitcher or glass that is large enough for the hydrometer to float without touching the sides or base. Transfer a sample of the liquid into the container.
- Throughout production, test the beer after signs of fermentation are over, but before including the yeast. Transfer the sample using a sterilized siphon, wine scoop or dropper.
- If accuracy is critical, flush the container with a small amount of liquid before adding a complete sample.
Step 4. Insert the hydrometer into the liquid
Once it's completely dry, lower it into the liquid until it's below where it would naturally float. It is important that the hydrometer sensor does not touch the sides or base of the jug when installing.
Step 5. Gently rotate the hydrometer
This dislodges the air bubbles attached to the tool, which would disturb the measurements. Wait until the hydrometer and liquid stop moving and the bubbles dissipate.
Step 6. Read the hydrometer scale at the lowest point on the liquid surface
The surface of the fluid can cling to the hydrometer and the walls of the container, forming a curve called a meniscus. Look for the scale marking at the hydrometer level with the lowest point on the fluid surface. Do not use the mark where it touches the hydrometer.
Step 7. Understand the measurement
The most common scale in hydrometers is "specific gravity". This is the ratio between the density of liquid and the density of water. Pure water will give a reading equal to 1,000. A higher reading indicates the liquid is denser (heavier) and a lower reading indicates the liquid is lighter.
The specific gravity of beer (or gravity, for producers) varies immensely. The more sugar is present, the higher the specific gravity and the higher the alcohol content present in the final beer. Most values are between 1.030 and 1.070, but they may be significantly higher
Step 8. Interpret the Plato, Balling or Brix scales
The hydrometer may use one of these scales or you may have to convert measurements in order to prepare a certain recipe. Understand here how to measure density using these three units:
- The Plato scale analyzes the percentage of sucrose in beer, so 10 degrees on this scale indicates that 10% of the content is sucrose based on weight. Multiply Plato's measure by 0.004 and add 1 for an estimate of specific gravity that is close enough for artisanal production purposes. A 10-degree beer on the Plato scale, for example, has a specific gravity of 10 × 0.004 + 1 = 1.040 (the farther away from this number, the less accurate the conversion).
- The Balling and Brix scales analyze the concentration of sugar present in a solution, but the units are close enough to the Plato scale so that they can all be used in artisanal production. Commercial breweries adopt more accurate conversion formulas and carry out their own tests to calibrate the Brix scale based on different factors.
Step 9. Get a reading of the final mix
At the end of the production process, test additional samples every day with the hydrometer. If the reading is the same two days in a row, there are no sugars still being converted to alcohol, which indicates that fermentation is complete. The final reading at this point is "final gravity". The target value will depend on the type of beer you are brewing and, in some cases, additional ingredients that affect the hydrometer reading.
- With rare exceptions, most beers have a final gravity between 1.007 and 1.015.
- Craft brewers rarely achieve the final gravity predicted by the recipe, especially in early recipes. The most important thing is that the beer tastes good, but keep the records and keep studying the process for a more consistent result.
Step 10. Estimate alcohol by volume
The difference between the original gravity and the final gravity indicates how much sugar has been converted to alcohol. The formula 132, 715 × (GO - GF) represents a useful method for converting this value to alcohol content. Note that this is only an estimate and is more accurate for beers with a final gravity around 1.010.
If the original gravity equals 1.041 and the final gravity equals 1.011, for example, the alcohol content is approximately 132, 715 × (1, 041 - 1, 011) = 3.98%
Method 2 of 2: Testing the Hydrometer
Step 1. Fill a container with water
To test whether the hydrometer is accurate, use either distilled or reverse osmosis water. If you are in the habit of using tap or untreated water in production, test it instead. Mineral content alters the results, but this will tell you how to adjust the readings for specific water-based beers.
Step 2. Bring the water to the correct temperature
The calibrated temperature of the hydrometer must be indicated on the hydrometer label or in the package instructions.
Step 3. Measure the density of the water
Put the hydrometer in the water, rotate it gently to stir the air bubbles, and wait for it to stop moving. The hydrometer will read 1000 for pure water if it is perfectly calibrated.
- A hydrometer using the Plato or Balling scale will read 0.00°.
- Read the previous instructions for a more detailed guide on how to use the hydrometer.
Step 4. Note correction if hydrometer is inaccurate
If the result is different from 1,000, the hydrometer is out of calibration (or the water contains minerals). Note the amount that must be added or subtracted in future readings to correct this error.
- If the hydrometer reads 0.999 for pure water, for example, add 0.001 to all measurements.
- For another example, if the hydrometer reads 1.003 with respect to tap water, subtract 0.003 from all measurements of liquids produced with that specific water. Test the hydrometer again if you have changed water sources.
Step 5. Consider changing or calibrating the hydrometer
If it is significantly outside the expected margin, it would be best to buy a new one. The old one may have lost its accuracy over time, but it's still possible that the frugal producer will be able to correct it.
- If the measurement is too low, apply masking tape, nail polish or other material capable of increasing the weight until the measurement is correct.
- If the measurement is too high, smooth the edges to eliminate material. Seal the rough area with nail polish to protect it from glass dust or sharp edges.
temperature adjustment
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Set the temperature on a standard hydrometer. If yours is calibrated at 15.6 °C, use the following table when measuring various temperatures. Find the temperature of the liquid in the first or second column and add the value from the same row in the third column for the specific gravity:
(Temp. (F)Temp. (°C)Setting5010−0.695512.8−0.386015.60.006518.30.537021.11.057523.91.698026.72.398529.43.179032.24.01){displaystyle {begin{pmatrix}{text{Temp. (F)}}&{text{Temp. (°C)}}&{text{Adjustment}}\50&10&-0.69\55&12.8&-0.38\60&15.6&0.00\65&18.3&0.53\70&21.1&1.05\75&23.9&1.69\80&26.7&2.39\85&29.4&3.17\90&32.2&4.01\end{pmatrix}}}
Tips
- Craft beer brewers can sometimes indicate specific gravity as two-place numbers. Reading 1,072, for example, may be referred to as">
- Commercial producers frequently analyze density throughout production and keep detailed records to track inconsistencies or store results from different methods. Therefore, there is a risk of contamination whenever the lid is opened. In a homey environment, it's usually best to check the beer as little as possible during production.
