Measuring Specific Gravity
The main purpose of measuring the specific gravity of your beer is to have a clear picture of how much sugar remains it it. Once wort is transfered to the fermenter you will take a sample of it and record its original gravity (OG) reading. From this point on a gravity reading should be recorded daily to measure changes in the sugars being consumed by yeast cells. Once the targeted Final Gravity (FG) is met you will be confident that the yeast has done its job and completed fermentation. By following a simple calculation you may now determine what the alcohol percentage of your beer is.
Alcohol By Volume = ((1.05 (OG – FG))/FG)/0.79 X 100
However many home brewers use the following formula
ABV = (OG – FG) X 131
This is a hydrometer (we sell them for between $7.99 & $9.99)……….
Here is an example of obtaining an OG. (FYI spinning the hydrometer in the test flask will eliminate bubbles)…
Another example, this time of a FG
Another tool for obtaining specific gravity measurements is a Refractometer. Refractometer’s take a brix reading that will need to be converted to specific gravity by doing some math or by plugging it into a computer program. The iphone has an app called the refractool which makes calculating your specific gravity from brix very simple. We also put a link on our homepage to an online brix converting formula for your convenience. In case you really want to do it on paper here is the formula…….
SG = (Brix / (258.6-((Brix / 258.2)*227.1))) + 1
This is a Refractometer (We sell for $79.99 in the shop)
An advantage to the refractometer over the hydrometer is that it only requires 3 drops of beer vs filling up a whole test flask.
Here is what you will see through the viewfinder. The ones we sell will automatically adjust for temperature.