Two of the tools we use to do this are the Saccharometer Hydrometer and the Alcometer/Alcoholometer/Proof and Tralle Hydrometer. Saccharometers measure the amount of sugar in a solution. Alcoholometers measure the amount of alcohol in a solution. How are the different, how are they the same? https://en.wikipedia.org/wiki/Hydrometer" onclick="window.open(this.href);return false;" rel="nofollow
https://en.wikipedia.org/wiki/Specific_gravitySpecific gravity is the ratio of the density of a substance to the density of a reference substance; equivalently, it is the ratio of the mass of a substance to the mass of a reference substance for the same given volume.
In our case, the reference liquid is water.
Sugar has a Specific Gravity of 1.59 at 20c.
Water has a Specific Gravity of 1.00 at 20c.
Alcohol has a Specific Gravity of 0.787 at 20c.
Temperature greatly effects the density (gravity). If you are not at the reference temperature your readings will be off. Temp correction for Saccharometer Hydrometer: https://www.brewersfriend.com/hydrometer-temp/" onclick="window.open(this.href);return false;" rel="nofollow
The key to understanding is this:
- When you mix water and sugar it is more dense than water alone.
- When you mix water and alcohol it is less dense than water alone.
If you have a device that is set to have the same density as water you can tell if your mixture is pure water or not. If you add a scale you can measure the difference to figure out how much of the secondary substance there is in the mix. If you have contaminates (anything that is is not sugar/water/alcohol) it will effect the SG reading so that it will not be accurate. AG mashes can have some contaminates but not generally enough to throw the hydrometer off by too much. Molasses is notorious for having tons of contaminates in the mixture. This is why the hydrometer will almost always show molasses washes as having much higher SG than the true level of sugar in the wash. Low wines and finished white spirits that have not had anything added to them should have no contaminates.
During fermentation alcohol is produced and sugar is decreased. The overall density of the wash will decrease. Once alcohol is present the Saccharometer will no longer accurately measure the amount of sugar in the wash. Gravity readings will read low once once fermentation starts. The more alcohol is produced the more the readings will be off. Without super expensive equipment there is no accurate way of measuring SG/ABV in a wash aside from obfuscation proofing. Luckily for the home distiller the true SG isn't meaningful. Apparent SG readings are fine to manage the fermentation process.
What's the biggest difference between the two?
The top of the Saccharometer is set the SG of water (1.000). This is why it rises as the amount of sugar goes up. By adding sugar you are increasing the density of the water/sugar mixture. If you put a Saccharometer in a mixture of water and alcohol it will sink. This is why at the end of ferments you can read the SG as being less than 1.000.
The bottom of the Alcoholometer is set to the SG of water. This is why it sinks as the ABV goes up. By adding alcohol you are decreasing the density of the water/alcohol mixture. If you put a Alcoholometer in a mixture of water and sugar it will float.
While they weigh the same or nearly the same, physically the Alcoholometer will have a larger bulb at the bottom.
Measuring Potential and apparent ABV
The Potential Alcohol (PA) of a wash can be estimated by a formula. It is an estimate and has many variables. Many calculators exist on the internet, just google it. The Apparent ABV of a wash pre-distillation can be calculated by calculating the OG PA - Apparent Gravity PA. This won't be accurate but for the home distiller it's close enough.
From our parent site: https://homedistiller.org/calcs/alcohol_content" onclick="window.open(this.href);return false;" rel="nofollow
Terminology:
Specific Gravity: See above for definition. For us, it's the measurement of an amount of water/sugar/alcohol in a liquid.
Apparent Gravity: Any uncorrected SG reading.
Starting or Original Gravity (OG): The gravity of a wash before fermentation starts.
Ending or Finish Gravity (FG): The gravity of a wash when fermentation is finished or when it is stopped.
Using Hydrometers:
https://52brews.com/how-to-use-a-hydrometer" onclick="window.open(this.href);return false;" rel="nofollow
https://www.essentialdistilling.com/res ... hydrometer" onclick="window.open(this.href);return false;" rel="nofollow
http://howtobrew.com/book/appendices/ap ... ydrometers" onclick="window.open(this.href);return false;" rel="nofollow
https://www.ttb.gov/spirits/proofing.shtml" onclick="window.open(this.href);return false;" rel="nofollow <-- TTB website on Proofing (including videos)
https://www.youtube.com/watch?v=inUwzYxoGUQ" onclick="window.open(this.href);return false;" rel="nofollow <- (Youtube) Still It: Hydrometers : Tips Tricks Traps
https://www.youtube.com/watch?v=dN0jkvynM9Y" onclick="window.open(this.href);return false;" rel="nofollow <- (Youtube) Barley and Hops: Hydrometer 101 Part 1: Saccharometer
https://www.youtube.com/watch?v=9pVJQDkBBlk" onclick="window.open(this.href);return false;" rel="nofollow <- (Youtube) Barley and Hops: Hydrometer 101 Part 2: Saccharometer
https://www.youtube.com/watch?v=U4rgCtw5TUs" onclick="window.open(this.href);return false;" rel="nofollow <- (Youtube) Barley and Hops: Hydrometer 101 Part 3: Alcoholometer