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Okay, we are just getting ready to open our doors and now I am stressing over proofing to TTB standards. In reality, how many are using a densitometer vs. hydrometer.  How difficult is it to Proof via hydrometer to TTB standards?  Lastly, how many are actually doing Proof by obscuration and if so how difficul is it? Are you using any special equipment beyond the petri dishes and scale?

 

thanks in advance

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We use a digital density meter, for the most part, during production as it is quicker and, I believe, more accurate than reading a maniscus.  However, for reporting, as the hand-held ddm is not certified, the final readings for reporting are made using glass alcohol meters.  No experience with overcoming obscuration measurements.

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dont stress about it too much.

as long as you are using certified stems, and a certified thermometer, should be just fine.

We eyeballed our proofing using hydrometers and thermometers for 15 years before we got our DDM 2911... and when we did, we did some side by side comparisons.. our manual measuring was usually within .05 degrees of proof... we were pretty satisfied by that 

 

That being said.. getting a density meter should be a goal of all distillers i think... these things are awesome. plug in a little sample, and badda bing badda boom your got your measurement AND records for proof

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Obscuration correction is annoying for the time it takes. Just get a little lab still and be careful as always with your measurements. Size the sample pulled to the proofing cylinder, which for me is 500mL. Rinse the tool used to measure, adding the rinse water to the boiling flask. Distill until just shy of 500mL is collected, then top off with pure water to exactly 500mL. Gauge this redistilled sample as your true proof, compare to the gauge before distillation for obscuration and correction. Be ready to repeat this a few times as you come down to bottling proof.

Glass is cheap, certification is not. I assume you don't want to spring for re-certification every six months. Get two sets of hydrometers. The one set are your babies and live in luxury, only being touched to in-house calibrate your workhorse hydrometers. The skills to calibrate hydrometers are exactly the same as to use them in the first place, just keep records.

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Distillers have been gauging their products successfully with hydrometers for over a 100 years and you shouldn't stress over that process.  The TTB have posted some excellent videos that show and describe the process in detail.  See https://www.ttb.gov/spirits/proofing.shtml

If you know that you have dissolved solids in your product then the first step is to measure them using the petri dish and scale method you mentioned.  If the total dissolved solids (TDS) content is less than 400 mg per 100 ml (or 4 gram per litre) then you are allowed to ignore the effect of the solids and use the standard TTB Tables.  If the TDS is between 400 and 600 mg per 100 ml (4 to 6 gram per litre) then you must use the TTB formula to adjust the apparent proof to get the true proof.  This is also described in a TTB video at the page I linked to above.  This formula applies to a fairly narrow range of proofs - 80 to 100 proof from memory but subject to correction.

If the TDS is above 6 gram per litre then you must use the lab scale distillation procedure also shown in one of the TTB videos linked above to get to the true proof. 

There are several useful discussions on this subject in previous threads and using "obscuration" or "lab distillation" in the search box at the top of the page will find them for you.

Once you know what your proof is, adjusting it to your target proof is a whole different kettle of fish.  As RobertS said above "be ready to repeat this a few times as you come down to bottling proof".  The more accurately you can measure the true proof and perform your proofing calculations the fewer times you will have to repeat the process.  Joe Dehner offered a manual procedure for these calculations in the thread

You can see the computer program that I finally developed as a result of all these discussions at http://www.katmarsoftware.com/alcodenslq.htm

and download a trial version if you want to test it.

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On 8/22/2017 at 4:45 PM, RobertS said:

Obscuration correction is annoying for the time it takes. Just get a little lab still and be careful as always with your measurements. Size the sample pulled to the proofing cylinder, which for me is 500mL. Rinse the tool used to measure, adding the rinse water to the boiling flask. Distill until just shy of 500mL is collected, then top off with pure water to exactly 500mL. Gauge this redistilled sample as your true proof, compare to the gauge before distillation for obscuration and correction. Be ready to repeat this a few times as you come down to bottling proof.

Glass is cheap, certification is not. I assume you don't want to spring for re-certification every six months. Get two sets of hydrometers. The one set are your babies and live in luxury, only being touched to in-house calibrate your workhorse hydrometers. The skills to calibrate hydrometers are exactly the same as to use them in the first place, just keep records.

RobertS.  I just got my TTB approval.  Can you explain in a bit more detail how you use your two sets of hydrometers?  Perhaps some detail or link on how to calibrate the workhorse.

Thank you.

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Check what type of calibration you have on your hydrometers, most are single or two-point calibrated. You will need a temperature-control bath to match the calibration temperature. This is a cheap and easy ice bath if they're calibrated to 32F/0C. If not, you'll need a temperature controlled bath. You use the calibrated set to proof down a calibration solution for each calibration point. Match the numbers on the certified hydrometer, then record the reading given by the workhorse at that point. Now you have the correction you need to apply to its readings. For single point calibration, it's a simple +/- you apply to future readings. For multi-point correction, you'll need to create a correction table based on however many points you took.

Use calibrated -> Match calibration point -> Record workhorse measurement at calibration point -> Calibration correction found

Your records will have the date and time of calibration, what master hydrometer was used, what it read at what temperature, what the workhorse read at the same temperature, and what correction that entails.

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Thank you RobertS.  I have not purchased the hydrometers yet.  I am reaching that now, which led me to ADI forums.   Sounds like single point is the easiest way to go.   

I have a lot to learn.   How long do the hydrometers remain "Certified"

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Ask your certifier. If you don't talk to them, they will assume regular use and only put it out to a year tops. Even if you can't push past a year, it's still good to be able to recalibrate twice for the price of once and be able to cheaply recover from the inevitable dropped hydrometer.

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