Hydrometer readings.

[FranklinNewhart]

I brew Apple Cider and I also brew a Freezer jacked Rum. I have a question concerning hydrometers. Start with the water. Both a brewing hydrometer and an Alcohol hydrometer will read at 0. Add sugar to the water to make a potential of 20% and add turbo yeast. The brewing hydrometer tells me the truth. Of course the alcohol one rides high in the liquid. So far so good.

Ferment until done. Both hydrometers are now back to reading 0 but there is now 20% by volume in the brew. So now I stick it in the freezer and jack it. After taking 50% of the water out of the mix through freezing it should now be 40%. Simple math. But the Alcohol Hydrometer is lucky if it says there is 10% there. I know the Hydrometer is accurate because I measured a bottle of purchased whiskey and it read 40% just like the label tells me.

Now my question. What is going on?

 

[dsniegocki]

Hydrometers do not measure alcohol, they measure density of liquid. This measurement is also affected by temperature. They can be used to approximate alcohol content by measure the density (specific gravity) of a fermentable liquid by performing a hydrometer reading both before (OG) and after (FG) fermentation, and then performing a calculation involving the difference of the two such as:

ABV = (OG - FG)/.75

 

[TheMadKing]

Hydrometers do not measure alcohol, they measure density of liquid. This measurement is also affected by temperature. They can be used to approximate alcohol content by measure the density (specific gravity) of a fermentable liquid by performing a hydrometer reading both before (OG) and after (FG) fermentation, and then performing a calculation involving the difference of the two such as:

ABV = (OG - FG)/.75

There are distillation hydrometers that measure "proof" of alcohol directly.

OP in answer to your question, 1 of 2 things is happening:

Either your yeast isn't making as much alcohol as you thought (likely)

Or you are removing alcohol along with the frozen water to some extent.

I would make sure you are measuring them all at the correct temperature though. My guess is that your distilling hydrometer is being thrown off by something, they don't work well unless its high proof alcohol ime

 

[ajdelange]

But the Alcohol Hydrometer is lucky if it says there is 10% there.
What is going on?

The brewing hydrometer is calibrated to read the specific gravity of the solution. If it has a Plato scale on it that is calibrated to read the percentage by weight of a binary mixture of sucrose and water.

The Tralle hydrometer is calibrated to read percentage of alcohol by volume (or double that if it is calibrated in proof) in a binary mixture of ethanol and water.

Neither a fermented cider nor one that has been frozen to remove a portion of the water is a binary mixture of water and sucrose or a binary mixture of water and ethanol. Thus neither instrument is suitable for determining the alcohol content of the jack or the cider. Alcohol is less dense than water and sugar and thus drives the SG down while the residual sugar drives the SG up. The two effects cancel and the specific gravity (which the brewing hydrometer does read correctly) goes down close to 1.000 or below. The SG is correct. You just can't derive alcohol content information from it.

I know the Hydrometer is accurate because I measured a bottle of purchased whiskey and it read 40% just like the label tells me.

That's because whisky is very close to a binary mixture of water and ethanol (the amounts of coloring and flavoring compounds in it are not significant compared to the amounts of water and alcohol). Check a bottle of anisette or limoncielo or sambucco. Those all contain things (dissolved sugar, lemon oil in the case of limonciello) that lead to 'proof obscuration'. Same with cider.

To get the ABV one must distill 100 mL of the beverage collecting nearly 100 mL of distillate and making up to 100 mL with DI water. The ABV of that distillate is then the same as the ABV of the sample. The ABV of the volume corrected distillate is determined with a digital density meter, a hydrometer or pycnometer. This makes 'proofing' a big PITA for any booze that contains more than 100 mg/L other stuff (other than alcohol and water that is).

 

[FranklinNewhart]

This is really helpful because it gives me the answer to my question. I will have to try doing the experiment. After I had froze the cider for the third time I did a shake test and it looks like it might be around 120 proof. By my calculation of how much water I had removed it also give me the impression of 60% by volume. On the third freeze I took into consideration the fact that Alcohol and Water will metastasize so I melted off two thirds instead of half to get all the alcohol I could.

 

[dsniegocki]

There are distillation hydrometers that measure "proof" of alcohol directly.

Wow, learn something new every day, haven't gotten around to distilling. Thx.

(quietly backs away from the thread...)

 

[TheMadKing]

Wow, learn something new every day, haven't gotten around to distilling. Thx.

(quietly backs away from the thread...)

I don't distill alcohol, nor to I advocate it or any other illegal activity. I'm just aware that the technology exists, and it is perfectly legal and acceptable to buy and own a hydrometer calibrated to measure the alcohol content of a water/alcohol solution.

 

[dsniegocki]

I don't distill alcohol, nor to I advocate it or any other illegal activity. I'm just aware that the technology exists, and it is perfectly legal and acceptable to buy and own a hydrometer calibrated to measure the alcohol content of a water/alcohol solution.

FWIW, I was only backing away from the thread because I obviously had no business rambling on about something I know nothing about.

 

[TheMadKing]

FWIW, I was only backing away from the thread because I obviously had no business rambling on about something I know nothing about.

Ha, I just didn't want you to be worried. I would be surprised if mods shut this thread down, since it's fairly innocent

 

[DevilNuts]

I saw a proofing hydrometer during a tour of a microdistillery. Unless they come in different sizes, the one I saw couldn't possibly have been mistaken for a brewing hydrometer. It was the size of my arm.

 

[TheMadKing]

I saw a proofing hydrometer during a tour of a microdistillery. Unless they come in different sizes, the one I saw couldn't possibly have been mistaken for a brewing hydrometer. It was the size of my arm.

They can be any size, the only thing that matters is that the scale is properly calibrated to the displacement of the tube.

They can be the same size as a SG hydrometer

 

[ajdelange]

Hydrometers can be made in any size you want as long as you adhere to the design equation. The important parameters are the ratio of the volume of the bulb to the cross sectional area of the stem and the ratio of the mass of the instrument to cross sectional area of the stem. If you want to double the sensitivity of a hydrometer you must double the mass or halve the cross sectional area of the stem. Clearly the stem will have to be twice as long (assuming you want the same range). If you double the mass you will also have to double the buoyancy of the bulb (by increasing its diameter and/or length).

 

[Morrey]

The brewing hydrometer is calibrated to read the specific gravity of the solution. If it has a Plato scale on it that is calibrated to read the percentage by weight of a binary mixture of sucrose and water.

The Tralle hydrometer is calibrated to read percentage of alcohol by volume (or double that if it is calibrated in proof) in a binary mixture of ethanol and water.

Neither a fermented cider nor one that has been frozen to remove a portion of the water is a binary mixture of water and sucrose or a binary mixture of water and ethanol. Thus neither instrument is suitable for determining the alcohol content of the jack or the cider. Alcohol is less dense than water and sugar and thus drives the SG down while the residual sugar drives the SG up. The two effects cancel and the specific gravity (which the brewing hydrometer does read correctly) goes down close to 1.000 or below. The SG is correct. You just can't derive alcohol content information from it.



That's because whisky is very close to a binary mixture of water and ethanol (the amounts of coloring and flavoring compounds in it are not significant compared to the amounts of water and alcohol). Check a bottle of anisette or limoncielo or sambucco. Those all contain things (dissolved sugar, lemon oil in the case of limonciello) that lead to 'proof obscuration'. Same with cider.

To get the ABV one must distill 100 mL of the beverage collecting nearly 100 mL of distillate and making up to 100 mL with DI water. The ABV of that distillate is then the same as the ABV of the sample. The ABV of the volume corrected distillate is determined with a digital density meter, a hydrometer or pycnometer. This makes 'proofing' a big PITA for any booze that contains more than 100 mg/L other stuff (other than alcohol and water that is).

Great information, AJ, and thank you for sharing. I use a distilling hydrometer to read ABV when I am distilling and making cuts. I never questioned the science of Tralle hydrometers until you made this post.

 

[Morrey]

They can be any size, the only thing that matters is that the scale is properly calibrated to the displacement of the tube.

They can be the same size as a SG hydrometer

Absolutely. My proofing hydrometer is the same size (almost identical) to the size of my brewing hydrometer.

 

[FranklinNewhart]

I don't distill alcohol, nor to I advocate it or any other illegal activity. I'm just aware that the technology exists, and it is perfectly legal and acceptable to buy and own a hydrometer calibrated to measure the alcohol content of a water/alcohol solution.

The type of distillation you are talking about here is in the realm of a laboratory experiment and it would be done in a glass lab distillation apparatus and not a moonshine still. A lab still is perfectly legal to own and use in a lab environment. To do it properly the globe flask would have to be suspended in an open beaker with the boil water in it. That way the entire 100 ml sample could be distilled without destroying the globe flask. That would give a more accurate reading.

 

[FranklinNewhart]

Absolutely. My proofing hydrometer is the same size (almost identical) to the size of my brewing hydrometer.

That is the problem with different Hydrometers. I have both in my kit and I used to have the one for making beer with the red and green colours on the scale but I broke it. The new one I bought looks almost like the Alcohol one and I have to look close to make sure I have the right one when I need to use them.

 

[Morrey]

Wow, learn something new every day, haven't gotten around to distilling. Thx.

(quietly backs away from the thread...)

Properly licensed distilleries are becoming more and more popular. Junior Johnson is a pretty famous gent in your area and is a licensed moonshine distiller in NC. The word licensed means the government has a tap into your pocketbook. Not all moonshine is illegal as it sits on the shelves of most liquor stores I have been in.

 

[ajdelange]

A lab still is perfectly legal to own and use in a lab environment. To do it properly the globe flask would have to be suspended in an open beaker with the boil water in it. That way the entire 100 ml sample could be distilled without destroying the globe flask. That would give a more accurate reading.

When we do a distillation in the lab for determining alcohol content the distillation flask goes into an electric 'mantle' which looks sort of like a birds nest made out of fiberglass with, obviously, electric heating elements and a thermostat in it. The analyst tweaks the thermostat to control the rate of boiling which can be a problem with beer because of the protein in it. One hundred ml of sample is mixed with 50 mL of water and 95 - 96 mL of distillate are recovered which are made up to 100 mL for the alcohol determination. The residue remaining in the flask is made up to 100 mL and the true extract determined from that.

 

[FranklinNewhart]

There are more than one way of doing a lab distillation. It could also be done with a vacume in which case there is no heat added at all.

 

[ajdelange]

I guess I'm confused as to what point you are trying to make here. I responded in No. 18 with the correct (ASBC MOA) method for doing the distillation in brewing to your post of an incorrect method which was advertised as being correct.

Yes, there are other kinds of distillation such as vacuum distillation, steam distillation and flash distillation but there would be no reason to use any of them when the task is to determine the alcohol content of beer, wine, mead or spirits.

BTW heat is often applied during vacuum distillation.

 

[FranklinNewhart]

I guess I'm confused as to what point you are trying to make here. I responded in No. 18 with the correct (ASBC MOA) method for doing the distillation in brewing to your post of an incorrect method which was advertised as being correct.

Yes, there are other kinds of distillation such as vacuum distillation, steam distillation and flash distillation but there would be no reason to use any of them when the task is to determine the alcohol content of beer, wine, mead or spirits.

BTW heat is often applied during vacuum distillation.

Perhaps to make note of the fact that not all small home labs have all the equipment they need to do all the experiments they would like to do. I was pointing out that there are alternatives. Now I know most people who have themselves some lab equipment would not likely have a vacume distillation setup but they might also not have that bird nest thing you are talking about with heat control in it. But they would probably have a large pot that they can suspend the distillation globe in and boil off the contents with it suspended in that pot of boiling water.

 

[ajdelange]

I'm still confused as you stated that the operation "would be done in a glass lab distillation apparatus" which consists, of a 250 mL distilling flask, Kjeldahl adapter, column, bridge, condenser (Alihn) and receiver. It is unlikely that a home brewer will have any of this but given that he does he is very probably going to have a proper mantle as well. Of course a bunsen burner would do though perhaps readers will share my nervousness about that when alcohol vapor is present.

In any case, a boiling water bath isn't going to work as, in order to recover 99% of the alcohol in the sample we need to collect 95 mL of distillate (remember that the flask is charged with 100 mL of sample and 50 mL of DI water the latter being used to rinse the volumetric flask into which the sample was measured thus insuring that all the alcohol in the sample is transferred to the distilling flask. Once the majority of the alcohol is distilled over (first 25 mL or so) the residue's boiling point is close enough to that of water that ebullition will cease. I suppose one could add enough salt to the water bath to get its boiling point up high enough but given that you have all that other gear (plus a digital densitometer or pycnometer plus analytical balance) the cost of a proper mantel is in the noise ($75 https://www.amazon.com/dp/B01G51VVF0/?tag=skimlinks_replacement-20).

 

[FranklinNewhart]

Let us see. Lets put together a buck-shee lab rig that will work. Start with a double boiler from the kitchen. Drill a hole in the lid and attach a piece of copper pipe along with a 90 elbow and a 45 elbow. Cap it and solder in a small fitting to attach your condenser. Now wind up a condenser with some tubing in a plastic water glass so you can bring the coil out a hole in the bottom that you seal with J B Weld. Seal the lid of the double boiler with flour paste after you put in the measured amount you want to distille. Fill the bottom with salt water. Dissolve as much salt as you can at just below boiling. Now you can distill it all. Right dry and get an accurate measurement. No glass lab equipment required. Totally McGuiver.

 

[TheMadKing]

Aaaand now we have come full circle to illegal distillation in your kitchen

 

[FranklinNewhart]

Aaaand now we have come full circle to illegal distillation in your kitchen

Didn't say I was going to do it that. Just saying there are other ways. Just to note I brewed Choke Cherry Wine in the summer of 1958 when I was still seven years old. Me and my sisters got Ka-Ka faced on it. What the law don't know . . . !!!!!!