Calculating Sugar Additions For Boosting Beer Gravity

In brewing, specific gravity is a measurement used to determine the density or weight of a liquid compared to water. It is useful for understanding the sugar content of a liquid, which can be taken before, during, and after fermentation. Pure water has a specific gravity of 1.000, so a reading greater than this indicates that the liquid is heavier or denser than water, while a reading lower than 1.000 means the fluid is lighter. In the context of beer, the specific gravity after the addition of sugar but before fermentation is known as the Original Gravity. To increase the specific gravity of beer, you can add table sugar, corn sugar, invert sugar, or rice syrup. The amount of sugar needed can be calculated by taking an initial gravity reading and subtracting that from the specific gravity you wish to achieve.

How to Calculate Sugar Addition to Increase Gravity in Beer

Calculating the post-boil OG

Calculating the post-boil original gravity (OG) is a crucial step in brewing beer, as it allows brewers to make any necessary adjustments to their recipe. By using a refractometer to measure pre-boil and post-boil specific gravity (SG), brewers can estimate their post-boil OG with reasonable accuracy. This calculation is done using the formula: Post-boil gravity points = (Pre-boil volume x pre-boil gravity points) / Post-boil volume.

To illustrate, let's consider an example. Suppose a brewer has a pre-boil volume of 7.5 gallons with a pre-boil specific gravity of 1.036. To calculate the projected post-boil OG, they would use the formula: (7.5 gallons x 36 gravity points) / 5.5 gallons = 49 gravity points. This calculation indicates that the post-boil OG is approximately 1.049.

It is essential to perform this calculation at the beginning of the boil, as it is the easiest stage to make adjustments. If the calculated OG deviates from the desired recipe target, the brewer can add additional extract or water to correct it. For instance, to increase the gravity of a 5-gallon batch by approximately 1 gravity point at the end of the boil, the brewer would add 2.5 ounces of light dried malt extract at the start of the boil. Conversely, to decrease the gravity of the same batch by about 1 gravity point, they would add 24 fluid ounces of water before boiling.

Additionally, brewers can adjust the specific gravity of their wort by adding sugar or dry malt extract (DME). To increase the specific gravity, corn sugar, invert sugar, or rice syrup can be added. The amount of sugar needed is calculated by taking the initial gravity reading and subtracting it from the desired specific gravity. The difference indicates how much sugar should be added. For example, if the current gravity is 1.075, and the brewer wants to achieve a gravity of 1.095, they would calculate: 31.0 (desired gravity) – 24.5 (current gravity) = 6.5, indicating that 6.5 ounces of sugar per gallon should be added.

Using a refractometer

A refractometer is a useful tool for measuring the specific gravity of unfermented wort. It can also be used to obtain information about fermented worts, such as the alcohol level in your beer and the original gravity from a finished beer.

Calibration:

First, calibrate the refractometer by cleaning the window and placing a drop of distilled or RO water on the glass. Close the cover and ensure that the glass has no dry spots or air bubbles. Wait for about 30 seconds.

Temperature Calibration:

Hold the refractometer level with the window facing a light source and look into the eyepiece. If you are using a model with automatic temperature compensation (ATC), you can skip this step. The meter will show a line between blue and clear, which corresponds to a scale on the side of the viewing screen. If you do not have ATC, use a temperature compensation chart to adjust the reading.

Taking a Reading:

Place a drop or two of your beer sample on the window and close the clear plate. Wait for about 30 seconds to allow the refractometer to become thermally stable and for the sample to spread uniformly. Then, look into the eyepiece to read the value.

Converting the Reading:

Most refractometers give a reading in Brix, which can be converted to specific gravity (SG) using the following formula:

SG = 1 + (0.004 x Brix)

Alternatively, you can use the "multiply by four" rule, where you take the Brix reading, multiply it by 4, and get the specific gravity in "gravity points." For example, if your Brix reading is 11, multiplying it by 4 gives you 44, which corresponds to a specific gravity of 1.044.

A more accurate conversion formula is:

SG = 1.000019 + [0.003865613(Brix) + 0.00001296425(Brix) + 0.00000005701128(Brix)]

Using this formula, a Brix reading of 11 would give a specific gravity of 1.043.

Understanding the Reading:

If your sample is just sucrose and water, you can take the refractometer reading directly. However, if you are testing wort, which is mostly maltose, you need to make a correction. Beers with very dark colours or high starting gravities may also require a different correction factor.

To calculate your correction value, first measure the specific gravity with the refractometer. Then, chill a sample of your wort and measure the gravity with a hydrometer. Convert the hydrometer reading to Brix using the equation:

Brix = (SG-1)/0.004

Next, divide the refractometer reading by your actual hydrometer reading. This number, which should be between 1.02 and 1.06, is your correction factor. Divide all your subsequent refractometer readings by this number to get the actual reading.

Software and Calculators:

While the math involved in using a refractometer can be challenging, there are software programs and calculators available to assist with the conversions, such as ProMash or the refractometer calculator provided by Northern Brewer.

Using a hydrometer

A hydrometer is a tool used to measure specific gravity using buoyancy to determine the density of a liquid. It is a straightforward device that measures the density of a liquid by comparing it to water. It usually comes with a thin plastic case to help protect it and uses a scale called specific gravity or just gravity for short.

The easiest way to use a hydrometer is to collect a sample of the wort (beer) using a sterilised and rinsed wine thief (pipette) and a trial jar. The trial jar is a specific jar used with the hydrometer for this purpose. A plastic jar is better than a glass one as the latter can break easily. The jar is 20cm long and has a diameter of approximately 3.5cm, with measurements on the side. This enables you to fill the right amount of liquid, leaving space at the top for the hydrometer to test the results.

• Using the trial jar with the hydrometer: Take the first measurement before pitching your yeasts once the wort has cooled down to the optimum temperature required for the yeast. This is commonly 20°C/68ºF for beer or wine and 15°C /59°F for lagers. This allows you to obtain the OG (Original Gravity). Many people say you can drop the hydrometer into the bucket containing the wort, but this is not recommended as it increases the risk of contamination and makes it harder to take an accurate reading. Instead, use a wine thief with a trial jar to draw the wort or must into the trial jar. Half-fill the jar to avoid spillage, then fully suspend the hydrometer into the liquid. Place the jar on a flat surface and carefully place the hydrometer into it.
• Obtain the Original Gravity Reading: You will notice that the surface of the liquid in the trial jar is slightly concave (U-shaped) - this is called the meniscus. Take the reading at the centre/base of the curve. This reading will enable you to work out how strong your fermented beer or wine is later in the process. It will depend on the beer or wine kit used, how much you diluted it, and how much sugar you added. A typical beer wort OG will be between 1.035 and 1.060.
• Calculate with Temperature: Knowing the temperature of the wort is critical for reading the original gravity (OG). The best practice is to use the hydrometer when the wort or must temperature is 15°C - 59°F for lager or 20ºC - 68ºF for beer or wine. Use a stick-on thermometer to measure the temperature of the main batch, avoiding the risk of ruining your brew by adding bacteria. If the temperature reading is different, you can use a table to work out the accurate reading.
• Obtaining the final gravity reading (FG): When the fermentation process is nearing completion or has completed, another hydrometer reading is needed to obtain the final gravity (FG). Be careful not to take this reading too soon, as it is recommended to only do two readings—one to obtain the original gravity and one to get the final gravity. At the final gravity stage, your wort is now officially a beer, and the final gravity reading should be close to the FG reading in the instructions of the home brew beer kit used. A typical beer's FG is between 1.015 and 1.005 and should be about 1/4th or 1/5th of the beer's OG.

By knowing the original gravity (OG) and final gravity (GF), you can determine how much alcohol has been produced and, therefore, the alcohol content of your beer. The ABV can be worked out by taking the start gravity from the final gravity and dividing this figure by 7.362.

Adjusting gravity by adding sugar

In brewing and fermentation, specific gravity is a measurement used for the density, or weight, of a liquid compared to water. Pure water has a specific gravity of 1.000, so a reading greater than this means the liquid is denser than water, and a reading lower than 1.000 means the fluid is lighter. In the context of fermentation, the specific gravity scale used ranges from 0.985-1.160.

The specific gravity of a liquid can be increased by adding sugar. This is because, as sugar is added to water, it increases the liquid's weight, which in turn increases its specific gravity.

To increase the specific gravity of wort, you can add corn sugar, invert sugar, or rice syrup. The amount of sugar needed can be calculated by taking an initial gravity reading and then subtracting that from the specific gravity you wish to achieve. The difference will determine how much sugar to add. For example, if your current gravity is 1.075 (24.5 oz. sugar per gal), and the desired gravity is 1.095 (31.0 oz. sugar per gal), then you would need to add 6.5 oz. of sugar per gallon [6.5 = 31.0 – 24.5].

It's important to note that the type of sugar you add can depend on the style of beer you are making. Additionally, you can also adjust gravity by adding dry malt extract (DME) or by diluting with water.

When it comes to beer-making, the specific gravity that is achieved after the addition of sugar but before the fermentation begins is known as the Original Gravity. This is a common term in beer brewing. The general idea is that the fermentation process will turn all of the sugar into alcohol, which results in a reduction in the specific gravity. This reduction in specific gravity can then be used to determine the alcohol by volume (ABV) of the beer.

Adjusting gravity by adding DME

If you've missed your original gravity (OG) target, don't worry—it's not hard to adjust the OG of wort as it goes into the fermenter. You can do this by adding water or dry malt extract (DME).

If your gravity is too low, you can add DME using the following calculation:

• Calculate the difference between your target and actual OG, then multiply by 1000. For example, if your target is 1.056, but you've got 1.048, this would give us (1.056-1.048) x 1000 = 8 points.
• Now, you need to raise your gravity by the number of points you calculated in step one per gallon of dry malt extract (DME) equivalent. Assuming a 5-gallon batch size, we need a total of 40 points of DME.
• DME has a potential of 1.046, which means it contributes 46 points per pound added. So, take the number of points you need and divide it by 46 to get the number of pounds of DME to add.

For example, if you need to raise your gravity by 8 points and are brewing a 5-gallon batch, you'll need to add 0.9 pounds of DME to your wort.

It's important to use a high-quality DME so that the flavour of your beer is not adversely affected. You can also use a refractometer to make these calculations easier and more accurate.

There are two distinct opportunities in the brew-day process to add the DME: near the end of the boil or before the boil. If you want more flexibility to correct your gravity, it's preferable to add the DME before the boil. However, if you add the DME near the end of the boil, you can extend the boil, which could result in a slightly more bitter beer.

Frequently asked questions