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Determining PG from volume and proof


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I don't have a proper floor scale to weigh tote and I have a 264 gallon tote full of 192 proof alcohol. How would I go about determining proof gallons and total volume after proofed down to 80?

Correct me if I'm wrong, but here are my calculations...

264 x 96%=25,344

25,344 x 2 = 50,688

50,688/100 = 506.88 PG

From there, I then determined total pounds of 506.88 PG at 192 P.

506.88/.28397 = 1,784.98 pounds

At 80 P, 506.88/.10093 = 5,022.09 pounds

So, does that mean I need to add 5,022.09-1,784.98 pounds or 3,237.32 pounds of RO water? Cheers.

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How are you measuring the 264 gallons? Is it off the plastic scale on the side of the tote? That is unlikely to be very accurate.

If that is so then there is no point in doing the calculations with such precision. By adding that exact amount of water you may well overshoot if there was not quite 264 gallons there.

You are better off adding less water, mixing well, then re-testing the next day. Hopefully you haven't overshot, re-calculate the amount of water to add, add slightly less.... slowly creep up on the 80 proof over 4 or 5 steps.

If you enjoy a bit of mental stimulation then you could add an exact amount of say 70% of theoretical water then calculate the final proof, and measure the final proof. If they are different then your initial volume was incorrect. You can then calculate the exact volume you started with, using TTB tables, or very easily with the calculator above (there is a free trial one in the link)

Use the "Blend Known Source Quantities" calculator and tweek the volume of 192 pr until it equals the proof you measured.

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Pete's suggestion of using the proofing process to confirm the quantity of 192 Proof spirit is excellent, and very easy to do.

Let us imagine that you add exactly 3,000 lb of RO water and after mixing and resting the diluted spirit measures 83.24 Proof. You can use the "Blend to Achieve Target Strength" calculator as before, but instead of setting the 192 Proof spirit (i.e. Source 1) as the known quantity you should set Source 2 as the known quantity because you know you added exactly 3,000 lbs of water.

Set the strength of the Target Blend to the measured 83.24 Proof and the calculator will tell you that you used 261.5 gallons of 192 Proof spirit.

Now the question is "how much additional water must I add to get to 80 Proof?". Click the "Copy Blend" button at the bottom of the window, and then click the "Paste" button in the top left of the Source 1 panel. This tells the calculator that you want to use your results from the previous blending as Source 1 in the subsequent blending. Change the target strength of the final blend to 80 Proof and the calculator shows that you need another 206.56 lbs of water (Source 2).



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That was a great question Mike.

I had considered buying a larger capacity scale as my production increases but know the certified ones are quite expensive.

You kicked my brain into gear and realized there is a very simple option. Maybe not so simple if you use TTB tables.

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The problem - TTB finds 26% of the distilled spirits products it tests in the market basket sample are ovenproof. Another 5% are under-proof. That's nearly 1/3rd out of tolerance.

The reason for the difference between the over and under percentages would seem to be that there is a tolerance for a drop below label proof, but no tolerance for proof above label proof, so any any over-proofing is an error.

Small distillers are assuredly the persons whose products fall outisidee of tolerance. The big guys are not giving product away, so I conclude a lot of you guys are. And the 33% error rate is 33% of the total number of samples pulled. Now, I don't know the how those samples are distributed between small and large producers, but since I assume that the large producers get things correct, that means that the percentage of errors among small producers is greater than 33%.

The reason is simple. Many small producers don't read the instruments correctly. Any calculations you make, by whatever method you choose, are going to depend on the accuracy of your readings of the apparent temperature and proof. You then make the adjustments to convert apparent to actually.

I know from experience that you can learn to proof accurately with a hydrometer, because I learned to do it and I'm hopeless about such things. I walk into a lab and things break. I had to "book" my experiments in high school chemistry and then throw in an error to make it appear my experiment had succeeded. So if I can do it, you too can learn to get accurate readings of the apparent proof. But until people learn to do that, errors are going to continue, no matter how you choose to determine the amount of water you need to make your cut. Pardon the pun, but there are no short cuts around accurate readings.

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