The Science of Sugary Water
In the world of brewing, winemaking, and distilling, we deal with "wort"—a liquid rich in sugars extracted from grain or fruit. The concentration of these sugars determines how much food is available for yeast, which in turn determines the eventual strength of the alcohol. Gravity is our map for this journey.
Gravity vs. Sugar Content
While **Specific Gravity (SG)** is the most common scale among homebrewers in the UK and USA, professional brewers often use the **Plato** scale, and winemakers typically use **Brix**. These scales measure the same thing: the percentage of sugar by weight in the liquid. For example, 10° Plato means that in every 100 grams of wort, there are 10 grams of dissolved sugar.
Why Monitoring Gravity Matters
Brewers measure the "Original Gravity" (OG) before fermentation starts and the "Final Gravity" (FG) once the yeast has finished its work. The difference between these two numbers reveals how much sugar was converted into alcohol and CO2. If your gravity stops changing but is still high, it may indicate a "stalled fermentation," requiring intervention to ensure the beer is shelf-stable and delicious.
Scale Conversion Table
| Specific Gravity (SG) | Plato (°P) | Brix (°Bx) |
|---|---|---|
| 1.000 | 0.00 | 0.00 |
| 1.040 | 9.99 | 10.00 |
| 1.080 | 19.34 | 19.37 |
| 1.120 | 28.06 | 28.14 |
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Frequently Asked Questions
What is Specific Gravity (SG) in brewing?
Specific Gravity is the ratio of the density of your wort or beer to the density of pure water. It indicates how much sugar is dissolved in the liquid.
How are Plato and Brix related?
For the purposes of brewing, Plato and Brix are virtually identical. Both measure the percentage of sucrose by weight in a solution.
What is the formula for converting SG to Plato?
A common approximation is Plato = (SG - 1) * 1000 / 4.