Looking for something between hydrometer and alcoholmeter to measure final gravity of wash.

Any hardware used for mashing, fermenting or aging.

Moderator: Site Moderator

potatofish
Novice
Posts: 8
Joined: Fri Apr 03, 2020 12:28 pm

Re: Looking for something between hydrometer and alcoholmeter to measure final gravity of wash.

Post by potatofish » Fri Jun 19, 2020 11:51 pm

You can always use a milligram scale.

Specific gravity is just density which is related to the weight of a volume of water on earth at sea level at a certain temperature. 1mL of water is 1 cubic centimeter of water and weighs one gram at 4C, or 0.99802g at 21C/70F. Check here for a table:

* https://blog.prepscholar.com/what-is-th ... y-of-water

Measure out a portion of liquid using a syringe (remember CC is cubic centimeter or 1mL) or a graduated cylinder of 1 - 5mL and weigh it. Divide the weight by the mL and multiply by the water density at your temp you have the specific gravity. For instance 5mL at 4.96g at 70F/21C is:

4.96 (weight of solution) / 5 (number of mL or CC) == 0.992 (call this D1)

0.992 (D1) * 0.99802 (density of 1mL or 1cc of water at 21C) = 0.9903548 (density of solution compared to density of water which is specific gravity).

As long as you can measure accurately and have a good scale this is an almost foolproof method and requires a trivial amount of solution and time.

Postscript: to measure the accuracy of your scale you can weigh coins. A new US penny is exactly 2.500g and a nickle is 5.000g (https://www.usmint.gov/learn/coin-and-m ... ifications).

User avatar
RedwoodHillBilly
Site Donor
Site Donor
Posts: 990
Joined: Tue Sep 01, 2015 7:30 pm

Re: Looking for something between hydrometer and alcoholmeter to measure final gravity of wash.

Post by RedwoodHillBilly » Sat Jun 20, 2020 12:12 am

That's all well and good, but can you get micro liter accuracy in your volume measurement?
John Barleycorn must die.
"and little Sir John in the nut brown bowl proved the strongest man at last.
The huntsman he can't hunt the fox, nor so loudly to blow his horn
and the tinker he can't mend kettle nor pots without a little barleycorn."

potatofish
Novice
Posts: 8
Joined: Fri Apr 03, 2020 12:28 pm

Re: Looking for something between hydrometer and alcoholmeter to measure final gravity of wash.

Post by potatofish » Sat Jun 20, 2020 12:58 am

You can get as accurate as your measurement tool allows. A volumetric pipette for example will be extremely accurate. Other pipettes (glass graduated, variable volume) are accurate enough for laboratory use. A syringe (you can buy them without poky needles and they are legal) is pretty accurate when used correctly and often accurate enough for lab use as well. A graduated cylinder can be good or it can be crap; if it is accurately marked it is as good as your use of it.

Can't really account for poor measuring practices or shoddy measuring equipment. However I would trust it more than the piece of paper inside of a blown glass tube used by most people to measure density in brewing solutions.

The real question though is: why does one need that much accuracy for hobby fermentation purposes? If the accuracy is that important you would have checked and calibrated gear and trained operators in controlled conditions, IMHO.

Hügelwilli
Novice
Posts: 86
Joined: Fri Feb 15, 2019 5:52 am

Re: Looking for something between hydrometer and alcoholmeter to measure final gravity of wash.

Post by Hügelwilli » Tue Jun 23, 2020 1:02 pm

RedwoodHillBilly wrote:
Sat Jun 20, 2020 12:12 am
That's all well and good, but can you get micro liter accuracy in your volume measurement?
With a pycnometer.
potatofish wrote:
Sat Jun 20, 2020 12:58 am
However I would trust it more than the piece of paper inside of a blown glass tube used by most people to measure density in brewing solutions.
This is true unfortunately.

A pycnometer and a fine balance is totally independent from something like an abv-scale. You don't even need a good calibration weight. But you need a 50 or 100g scale with a resolution of 1mg at least. Then you have something much more precise than normal alcoholmeters, hydrometers or refractometers.

Post Reply