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Correcting ABV by adding GNS


Brothers Vilgalys Spirits

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Stupid n00b question from a relative first-timer (We just got our COLA! Time to bottle some spirits!)

I make a liqueur with a target of 40% ABV. So far I've made 4 batches, all of which are a little bit less than that. First batch, for example tests at 36.75% ABV after re-distilling a sample. I went a little bit under on purpose with the plan of testing the proof and adding a bit more GNS to get the liqueur to the right bottling strength.

And now that I'm attempting to calculate how much GNS-190 to add, I'm realizing this may have been much easier the other way around. The dilution calculators and examples that I see out there are geared towards diluting barrel-proof or high-proof spirits with water, not adding GNS to bump up an under-proof batch. I would see what AlcoDens can do for me, but I've got a mac.

I was once good at chemistry (like in high school) but evidently I profoundly overestimated how much of that I've retained.

Can anyone help me get me in the right direction?

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Using the amount of alcohol you currently have in solution, calculate the total volume that would make 40%. Calculate what that volume would weigh. Now weigh your underproofed volume. The difference in the 2 weights is how much excess water you have in your underproofed volume. Now, you know how much water you have by weight and you can look up the gallons per pound of water, 190pf and 80pf. From there its pretty straight forward to calculate how many pounds of 190 proof to combine with the water to get a 40% solution.

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Just to make sure we are on the right track here, I assume when you say "liqueur", you have an alcohol solution that you have added sugar and flavours to.

To test the ABV you appear to have run a sample through a bench still to leave the sugar etc behind. Am I correct?

For anyone reading this who is new to distilling, a hydrometer is useless when trying to measure alcohol content of spirits containing sugar.

JarHead, would you mind posting the calculations, assume we start with say 100 lbs of liqueur. I think the calculations are not quite as straight forward as you suggest.

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I suspect that JarHead's procedure comes unstuck at the point where he says "Calculate what that volume would weigh". I do not know of any data available to give the density as a function of sugar and alcohol content. If anybody knows if that data does exist somewhere I would very much like to get hold of it.

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BV, did you know you can run a PC emulator on your Mac? Or you can get a cheap PC just for AlcoDens. You can probably get on one Craigslist for less than the cost of the AlcoDens license.

Now with that said, I think your idea of aiming higher than the target proof is probably better than adding neutral. Why don't you distill another batch to a higher proof and add that back in as needed? I suspect the flavor would be better that way too.

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Pete, thanks for confirming that. I am using a lab still to distill out the alcohol, then diluting back to the original volume with distilled water before testing with a hydrometer.

I do know the current density of the product as-is, which should get me started, correct? I'm making this on a pretty small scale (30 gallon batches) right now, would alcohol-water contraction be a major factor at this level? To cause more difficulty with simply 'calculating' this, I'm using honey (not just sugar) which can have a variable water content of a few % depending on season, storage, extraction, etc.

Will have to try both methods (adding GNS to balance, and adding water / extra strength liqueur), and apparently run a bunch of sample distillations till I get this right. I'm thinking things should be easier once I've worked out the ideal weight of all the ingredients in each batch.

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Although I am usually quick to point out the disadvantages of the Pearson Square for blending spirits, in this case I would give it a try. Your current strength of 36.75% ABV is so close to the target of 40% that you should not be too far out. Pearson gives a value of 5.9 volumes of 95% ABV for each 100 volumes of 36.75% base. Using AlcoDens and taking the honey and water solution as just water gives 5.7 volumes.

When Pearson is used to calculate the quantity of water required to dilute a spirit it underestimates the quantity needed. Here we are coming from the other side, so it over estimates.

I think the important thing is to keep good records of what you do and what happens, and build up your own graphs or tables. I would try adding 5.7 volumes for each 100 volumes you have, and then re-measure (and record the results). I don't think you will be far out. Although the sugar content is high, it is not changing much between where you are now and the final target, so hopefully it won't have too much influence on the dilution calculations. Of course any reading taken with an hydrometer will be way out - I guess your current spirit is showing an ABV close to zero on the hydrometer?

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Mr Vilgalys, If you give me a bit more information I will have a play with some calculations to see if I can sort this problem. I think it will be a bit too complicated to work from the current density. I am pretty sure there is volume contraction with a honey water mix.

If it is not a trade secret, how many lbs of honey are you adding to your spirit?

What was the ABV of the spirit before you added the honey?

If it was 40% then the water in the honey is what caused the dilution.

Honey is about 18% water so if I know original ABV and lbs honey I can check. It should then be quite easy to work out how much more 190 pr to add.

IF that all works then I should be able to show you how to calculate amounts for future batches.

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Pete that would be awesome. Saturday I'll be back at Bros V HQ and take a look at the batch notes, then I'll message you with the info.

Looking forward to a bit of brain excersise

I have been sent some density tables of various honey sugars dissolved in water. With a few random calculations it appears as if there is very little volume change when mixing, in some cases a very slight expansion but not enough to worry about.

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Sorry guys, I was a little brief. Here is how I do it. All this assumes that you know how much alcohol you started with, preferably by weight, and you determined the proof by distilling a known volume of the liqueur, collecting all the alcohol, replacing the missing volume with water, keeping temp constant, etc and then measuring the proof. The key is to take the sugar content out of the equation. It’s irrelevant when you calculate the proof, so just assume that you’re working with alcohol and water. If you have significant alcohol loss from the maceration then it isnt this straight forward, but I always make a syrup by weight and measure its density so I can make weight corrections easily. Also, by weighing the pre-proofed sample and the proofed result gives you a relative density of the two so you can take out the dissolved solid component of weight. It also helps to have a laboratory still, a precision bench scale and a water bath.

Lets assume that the proof you got was 74. And you started with 100 lbs of 190 proof.

Then 100lbs *.14718 lbs/gal (table 4) = 14.718gal @ 190pf => 13.98gal @100% => 37.78 gal @ 74 pf

=> 37.78 gal / .12557lbs/gal = 300.87 lbs = W1 (this is what it would have weighed if you just were using water and alcohol.)

Now, 13.98 gal @ 100% => 34.95 gal @ 40% abv (80pf)

=> 34.95 gal / .12616 lbs/gal = 277.03 lbs = W2

W1 – W2 = 23.84 lbs excess water

So, how much 190pf to add (lbs) to get to 80pf when you have 23.84lbs of water?

Total Weight (T) = Weight(190) + Weight(H2O) = W(190) + 23.84

Total weight is also equal to: T = 190/80 * (.14718/.12616) * W(190) (here is where the magic happens)

W(190) + 23.84 = 2.375 * 1.1666 * W(190) = 2.77 * W(190)

=> 23.84 = 2.77 * W(190) – W(190) => 23.84/1.77 = W(190)

=> W(190) = 13.47 lbs

(Sorry for those of you who didn’t want an algebra lesson.)

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JarHead, where were you when Will issued a challenge of a similar nature see http://adiforums.com...topic=769&st=40

No one had worked it out after a couple of years. I stumbled across it and posted several ways of solving the problem.

Your approach is slightly different again, but still using algebra.

I checked your answers with Alcodens and your algebra is quite correct :D 10/10

Firstly I have no practical experience with adding sugars to spirits so I am just trying to learn.

If I understand your post just above, you assume that 1 volume of sugar (calculated by density) + 1 volume of water + 1 volume of pure alcohol will give you the same total volume as 2 volumes of water + 1 volume of alcohol !!

By referring to density tables, when adding sugar to water there is very little total volume change, (sometimes a very silght increase) so for practical purposes that takes one complication out of the equation.

But I am still suspicious that a sugar/water solution will not have the same contraction as a pure water when alcohol is added. (especially with high sugar content)

Brothers Vilgalys PM'd me their exact quantities (I won't post them here without their permission) and I did the calculations several ways. When I assumed there was normal volume contraction with the efhanol+water but no contraction with the honey, I came up with almost the exact ABV they found in their test sample.

OK, one batch made by a noobie doesn't "prove" anything but it is enough to make me ask questions

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  • 2 weeks later...

Pete, thanks for confirming that. I am using a lab still to distill out the alcohol, then diluting back to the original volume with distilled water before testing with a hydrometer.

I do know the current density of the product as-is, which should get me started, correct? I'm making this on a pretty small scale (30 gallon batches) right now, would alcohol-water contraction be a major factor at this level? To cause more difficulty with simply 'calculating' this, I'm using honey (not just sugar) which can have a variable water content of a few % depending on season, storage, extraction, etc.

Will have to try both methods (adding GNS to balance, and adding water / extra strength liqueur), and apparently run a bunch of sample distillations till I get this right. I'm thinking things should be easier once I've worked out the ideal weight of all the ingredients in each batch.

The Obscuration method of proofing is a tedious process..... Are you doing the volume measuring at 60f ?
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I still haven't had any replies to my question

Does a sugar/water solution have the same contraction as a pure water when alcohol is added. (especially with high sugar content)?

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  • 1 month later...

To take 80 proof down to 40 proof it is not nearly accurate enough to add equal volumes.

You need to take 1 volume of 80 and add syrup until you have exactly 2 volumes. That allows for volume contraction, if any, of the syrup

The problem starts when you try to measure volumes very accurately.

Firstly the temperature needs to be at the temp of the calibrated measuring vessels.

A calibrated glass measuring cylinder is not accurate enough for TTB

A certified volumetric flask (they have a large body with a narrow neck) at 60F (or 20C) would probably get close enough, but you would need two, one with twice the volume of the other just to do a 50% reduction. Then you would have to wait some time until the temperature of the mix dropped back to 60F (diluting produces heat) and hope you haven't overshot. etc..etc.

As has been said before, diluting by mass is much easier to get it accurate.

But in this case I am not sure if the TTB tables can be used to calculate the weights because I am unsure if high sugar syrups contract the same as pure water.

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Thanks Pete. I had figured that the simplicity of a 1 to 1 ratio would be complicated by density (and of course temperature), but had no idea how much. A place in Portland Oregon has a wide variety of fruit liqueurs all at 40 proof. I don't know how they hit that round number easily and repeatedly, or how the TTB polices it.

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