Hand Sanitizer Hydrometer Reading offset?

[Jedd Haas]

FDA states that the alcohol content should be verified and that a hydrometer reading is one of the acceptable methods.

In the WHO guide, they show a hydrometer apparently reading 80% ABV, then state further that for "an isopropanol solution, a 75% solution will show 77% (± 1%) on the scale at 25°C."

The WHO guide does not state a temperature for the (apparent) 80% ABV reading.

For the ethanol formula, do the additional ingredients, particularly the glycerine, affect the hydrometer reading? If so, how much of an offset is there?

Or should the hydrometer simply be read as-is and temperature-corrected to 60F per normal procedure?

 

[CalwiseSpirits]

My interpretation is that it is meant to be read as-is. We have a + or - 5% tolerance which is pretty wide anyway.

[John Bassett]

8 hours ago, Jedd Haas said:

FDA states that the alcohol content should be verified and that a hydrometer reading is one of the acceptable methods.

In the WHO guide, they show a hydrometer apparently reading 80% ABV, then state further that for "an isopropanol solution, a 75% solution will show 77% (± 1%) on the scale at 25°C."

The WHO guide does not state a temperature for the (apparent) 80% ABV reading.

For the ethanol formula, do the additional ingredients, particularly the glycerine, affect the hydrometer reading? If so, how much of an offset is there?

Or should the hydrometer simply be read as-is and temperature-corrected to 60F per normal procedure?

 

I have been proofing as usual.   I too wonder what effect glycerin, hydrogen peroxide, denaturants, etc. have on actual proof.   The labs are behind 20+ days

[DrDistillation]

Just follow the recipe PER FDA if in the USA as given checking it when they tell you to and you'll be fine.

[SCLabGuy]

On 4/6/2020 at 6:29 AM, John Bassett said:

I have been proofing as usual.   I too wonder what effect glycerin, hydrogen peroxide, denaturants, etc. have on actual proof.   The labs are behind 20+ days

Here's my guesses
- If you use 5% Isopropanol as your denaturant you will have a hard time proofing accurately using normal methods because Iso has a much lower density than ethyl and you've made a mixture. This renders traditionally-calibrated instruments like hydrometers and density meters pretty much useless without a fudge factor of some kind.

- If you use formula 40A/40B with denatonium benzoate the application rate is so low (1.7 grams per 100 gallons) that its effect on proof can be ignored safely

- Glycerine being much denser than ethyl will have an obscuring effect on the proof (just like sugar syrup or molasses would)

- H2O2 is in such a small quantity that I think it will have a very small effect on proof, if any

 

We'll be making a number of large batches in succession and I will test product at each step of the process in a density meter w/ refractometer.  If warranted, I will even bench distill a sample.  I'll share my findings.

FDA told us on the phone (but refused to go on record) that they chose the 80% ABV level because it is thought to be the most effective against COVID-19.  That motivates me to get the proof right, even though we do have a rather large window (+/- 5% ABV) as a practical matter.

[DrDistillation]

You're making this to complicated. No fudge factor required or wanted.  You're denaturing at 20:1 and using it as is as measured after denaturing.

Pick batch total volume target you will make.  Calculate the Glycerin & Hydrogen peroxide needed per batch size per FDA (usa) for that size batch.

Glycerin (glycerol) needs to be 1.45% v/v for the total batch size

Hydrogen peroxide at 3% needs to be 0.125% v/v of volume size

Calculate Ethanol needed for batch size depending on your ABV.

Add water to achieve 80% after all ingredients are mixed well and rested.

----

If you're having an issue trying to calculate this shoot me a PM with your measured ABV after mixing in the 5% Isopropanol to your Ethanol.  Just give me the ABV of the mixture and % of Hydrogen peroxide you have on hand.

Tell me the batch size you're targeting (in liters) and I'll send you back the amount of each ingredient you need to hit your batch size at 80%.

[SCLabGuy]

The firm uses the most accurate method of analysis available at the site for verification of alcohol content in samples of the finished drug product before each batch is released for distribution.Methods can include gas chromatography (GC), alcoholmeter, hydrometer, or other chemical analysis of at least equivalent accuracy. The sample tested can be performed on in-process material before filling into the final containers to be distributed.

FDA wants you to proof batches before bottling.  This discussion is about that.  Designing a batch to land at 80% ABV as you describe, and objectively verifying the alcohol content, are two separate things.  Anyone can use hoochware or letsmakesomesanitizer.com and get a formula - that's the easy part.

[meerkat]

Hi @Jedd Haas  - please can you point me to the FDA recommendation that the alcohol content should be verified with a hydrometer.  I have not been following the sanitizer threads closely and am not up to speed on the regulations.

Using a hydrometer to check the final product will indicate if there are gross mistakes, but it is not sufficient to truly verify the composition of the product. It will tell you if your formulation is wrong, but will not confirm if it is correct.

Here are a few of my observations that may help you good people helping us all out by providing the much-needed sanitizers.

Isopropanol has a very similar density to ethanol. My estimate is that if you substitute 5 parts by volume of the ethanol in a 160 proof spirit with 5 parts of isopropanol then the apparent proof would increase to 160.16. In a non-potable product I would guess this is negligible.

The glycerol and peroxide are both heavier than ethanol or water, so they will definitely obscure the ethanol. Unfortunately both are lighter than sugar, so I can't push my blending calculator here!

I have tried to work out obscuration rules for glycerol and peroxide in the same format that the TTB uses for sugar. The TTB uses the units of 100 mg of sugar per 100 ml of spirit. This is equivalent to 1000 mg of sugar per 1000 ml of spirit or 1 gram per liter, which I find a much easier unit to work with, so I will quote everything in those terms, but the numbers are actually the same as what the TTB uses.

[Edit April 10: After doing more calculations together with @SCLabGuy we found that the numbers below were a bit too high.  My latest number for glycerol (the only bit that really counts) is 0.12 Proof per gram/L.  This makes it even more reasonable to use a hydrometer to check the final  product - as the FDA recommends.  End Edit]

For glycerol I come to 0.23 Proof per gram/L and for peroxide 0.29 Proof per gram/L. These would be specifically for an 80 % ABV alcohol content and would definitely vary with the alcohol strength. These numbers compare with the 0.4 Proof per gram/L the TTB gives for sugar in 80-100 proof spirits.

Glycerol at 1.45 v/v is equivalent to 18.3 gram/L so the obscuration would be 18.3 x 0.23 = 4.2 Proof. Peroxide at 0.125 v/v is equivalent to 0.181 gram/L, making the obscuration 0.181 x 0.29 = 0.05 proof and probably not worth worrying about.

So if we ignore the variance caused by the isopropanol and the peroxide we can say that the apparent proof should be 160 - 4.2 = 155.8 Proof. Some formulations recommend half the glycerol (i.e. 0.725 v/v) and then the apparent proof would be 160 - 2.1 = 157.9 Proof.

Please note that these are all theoretical calculations and you should verify everything with actual measurements.  I look forward to @SCLabGuy showing his lab results to see how close we can get with calculations.

If my numbers need to be expressed in different terms to make them more useful in practice please let me know and I can rework them.

Edited April 10, 2020 by meerkat
Error in calculation

[SCLabGuy]

4 hours ago, meerkat said:

For glycerol I come to 0.23 Proof per gram/L and for peroxide 0.29 Proof per gram/L. These would be specifically for an 80 % ABV alcohol content and would definitely vary with the alcohol strength. These numbers compare with the 0.4 Proof per gram/L the TTB gives for sugar in 80-100 proof spirits.

Glycerol at 1.45 v/v is equivalent to 18.3 gram/L so the obscuration would be 18.3 x 0.23 = 4.2 Proof. Peroxide at 0.125 v/v is equivalent to 0.181 gram/L, making the obscuration 0.181 x 0.29 = 0.05 proof and probably not worth worrying about.

Thanks for the very helpful shortcuts.

Two questions:

- Can you show your process for arriving at those obscuration numbers?

- Using that math, can you consider expanding AlcoDens LQ's "sugar syrup" functionality to be more flexible and allow the calculation of non-sugar obscuration for other ingredients like molasses & glycerine?

 

4 hours ago, meerkat said:

Hi @Jedd Haas  - please can you point me to the FDA recommendation that the alcohol content should be verified with a hydrometer.  I have not been following the sanitizer threads closely and am not up to speed on the regulations.

https://www.fda.gov/media/136289/download

Point #6 (I quoted it above)

[meerkat]

@SCLabGuy - I am happy to share the calculations for the obscuration numbers, but I doubt whether many would be interested to see them here.  They are hand-written and I will send you a scan if you write to me at the support address given in my software.

The calculations in AlcoDens LQ are based on hard data and not on theoretical calculations. This is important for the contraction calculations, which are totally neglected in the simple obscuration estimates I have done for the glycerol. I would be reluctant to add untested calculations into the software.  And I get too many people saying that the software needs to be simplified for me to go the other way and add in extra complications and options.

Thanks for the pointer to the FDA guidelines.

[Jedd Haas]

8 hours ago, meerkat said:

Glycerol at 1.45 v/v is equivalent to 18.3 gram/L so the obscuration would be 18.3 x 0.23 = 4.2 Proof. Peroxide at 0.125 v/v is equivalent to 0.181 gram/L, making the obscuration 0.181 x 0.29 = 0.05 proof and probably not worth worrying about.

So if we ignore the variance caused by the isopropanol and the peroxide we can say that the apparent proof should be 160 - 4.2 = 155.8 Proof.

@meerkat That is exactly the information I was looking for. Thank you. The FDA guidance also states that a 5% ABV tolerance is acceptable, so 4.2 proof would be 2.1% ABV and well within the acceptable tolerance.

@SCLabGuy quotes above the section of the FDA guidance I was referring to in the initial post.

I will be using Bitrex for denaturing, so the change to apparent proof caused by isopropanol will not be a concern for me.

[meerkat]

This post is just to pull this thread to the top again.  I have made an edit to the obscuration factor that I had calculated above for glycerol and I would like anyone who has used the old number to be aware of the change.

@John Bassett @CalwiseSpirits @Jedd Haas @DrDistillation @SCLabGuy

[John Bassett]

8 minutes ago, meerkat said:

This post is just to pull this thread to the top again.  I have made an edit to the obscuration factor that I had calculated above for glycerol and I would like anyone who has used the old number to be aware of the change.

@John Bassett @CalwiseSpirits @Jedd Haas @DrDistillation @SCLabGuy

So, we are looking at 18.3 x .12 = 2.196 proof versus 4.2 for glycerol?

[meerkat]

@John Bassett Yes, that is correct.  The final product should have an apparent proof of 157.8 if its true proof is 160.

[John Bassett]

Thanks @meerkat.  Once again, you come to the formula rescue.