Wort Gravity

SG/Plato/Brix and Temperature

Measuring the Wort Gravity

How to use the hydrometer correctly

The specific mass densimeter , better known by brewers as simply densimeter, is an essential instrument for home brewers, as it is with it that you will measure the density of your wort and usually has a graduation between 1,000 kg/m³ (which is the density of pure water) and 1,100 kg/m³.

With it you will measure the concentration of sugars in your wort , allowing you to know the original density (Original Gravity – OG) of your wort, as well as the attenuation of sugars in your wort by yeasts, measuring final density (Final Gravity – FG) at the end of its fermentation.

There is no mystery about how to use the hydrometer, as it is a very simple activity .

You will only need a beaker (a 250 ml is fine), a thermometer (to measure the wort temperature and then you will know why this is essential) and a small sample of your wort.

After placing your wort sample in the beaker, you will insert the hydrometer into the beaker with the wort and give the hydrometer a slight twist with your fingertips.

TIP: The turn on the hydrometer is so that it doesn't touch the walls of the beaker and, thus, you can get the correct density reading of your wort. Remember to measure the wort temperature also when taking the density reading.

How to take a density reading?

To read the density of your wort , you need to align your eyes with the level of the liquid and see which graduation line the liquid is “touching”. So you can visualize the correct density.

TIP: Put always your hydrometer on a flat surface and preferably leveled before reading. Do not attempt to read holding the beaker in your hand, as the chances of you recording an incorrect density are considerable.

Correcting the reading according to the wort temperature

Hydrometers are calibrated at the factory normally at a temperature of 20°C , so it is necessary to correct the reading you have measured if your wort temperature is above or below 20°C. The difference between your measurement and the corrected density can be considerable!

To correct the reading, the table below can used, there are also applications for your cell phone (BrewMath is an example), Beer Smith brewer software or other software that also do this conversion.

Just check the temperature of your wort, check the correction value from the table and add it to your reading.

If you, for example, measure a density of 1,050 kg/m³ and a temperature of 73°C, your corrected density will be 1,072 kg/m³, it means 1,050 + 0,022 = 1,072.

One suggestion is that you separate at least one sample , lower the temperature to 20°C and take the measurement to confirm that your corrected density reading is correct.

For example, if your wort is at 60°C, you will measure the density, make the correction using the application on your cell phone or brewery software or even the correction table and you will have the value of what the density would be at 20 °C.
Then you leave this beaker with your wort to cool while you continue the brewing process.
When it has reached 20°C you take the reading again and check if it is the same as what you found by making the correction . Sometimes there may be something between one or two units and you can correct for your future readings.

TIP: Do not put the wort you used to measure the density back into your fermenter, as you may have contamination issues with your beer.

Conversion Table - Brix / Plato /SG (Specific Gravity)

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