Any automated way to measure gravity during boiling stage?

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brew_kaka

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Hello homebrewers,

I was wondering if anyone has tried any automated way of measuring gravity during boiling stage? I often have to do adjustments to my water level before I cool the wort for fermentation to get the right pre-fermentation gravity. I usually take a sample, cool it down to ~25 degrees and then use refractometer/hydrometer to check the gravity. Let me know if anyone has tried anything to measure this digitally or any other automated way?
 

RM-MN

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My refractometer says it is temperature compensated. I grab a sample of boiling wort and put a couple drops onto the glass, close the cover and read the gravity immediately. I don't add adjustment water until the wort is chilled to pitching temp.
 

McMullan

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At homebrew level, no. Far too expensive to justify. Your best bet, and much cheaper, although still quite expensive, is an EasyDens density meter.
 

bracconiere

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i had an idea....some stir bars in a ptfe ball...get the cm3 of the ball, then fill it with right amount of weight of stir bars for your desired gravity....


when it floats to the surface it's done? what do ya think @McMullan ?

edit: some sort of boiling proof fillable ball, if you know the cm3 of it, you could just add the weight of your desired finish gravity couldn't you? and when the sugar is concentrated enough it would float on the surface? or SS balls or a very small water bottle?
 
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McMullan

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One of these?
il_fullxfull.1983355837_3mgp.jpg

It's a crystal ball with super handy rope netting to facilitate fishing it out of the kettle when done.
 
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balrog

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I suggest taking good notes. Repeatability of boil off rate & grain absorption will give you your desired final volume results after a couple of batches.

Unless, like me, you fudge up a beginning volume fill because you're in a hurry every so often...
 

pvtpublic

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It comes down to knowing your boil off rate. If you can keep it consistent, it's easy to figure out. For example; I have exactly a 1 gallon per hour boil off rate in my set up. I always do a 90 minute boil and I start with 7 gallons and end with 5.5 gallons. Every time. If I'm going to shoot for a 1060 OG, I would calculate my gravity units in my wort by using the last two digits in the specific gravity. So 60 × 5.5 = 330 points. So no matter what the volume of liquid in my kettle, it needs to contain 330 points. So to figure my preboil gravity, I divide that 330 by 7 gallons to get a preboil of about 47. So when I lauter, I'm looking for 1047. I also lauter 9 gallons into 3 different pots so that I can blend them to get exactly gravity that I want, in this example 1047. I use those same calculations to figure the gravity points of all three pots. Ever since I started doing this, I've always hit my target.

It's a lot more simple than I just made it seem, I promise.
 

RogerGrahl

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It comes down to knowing your boil off rate. If you can keep it consistent, it's easy to figure out. For example; I have exactly a 1 gallon per hour boil off rate in my set up. I always do a 90 minute boil and I start with 7 gallons and end with 5.5 gallons. Every time. If I'm going to shoot for a 1060 OG, I would calculate my gravity units in my wort by using the last two digits in the specific gravity. So 60 × 5.5 = 330 points. So no matter what the volume of liquid in my kettle, it needs to contain 330 points. So to figure my preboil gravity, I divide that 330 by 7 gallons to get a preboil of about 47. So when I lauter, I'm looking for 1047. I also lauter 9 gallons into 3 different pots so that I can blend them to get exactly gravity that I want, in this example 1047. I use those same calculations to figure the gravity points of all three pots. Ever since I started doing this, I've always hit my target.

It's a lot more simple than I just made it seem, I promise.
Excellent, terrific advice. If you don’t want to do the calculations given in pvtpublic’s reply, you can use brewing software (e.g. BeerSmith, Grainfather) instead.
 

schmurf

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I wish there was an inline device you could attach to your recirculation that would give you constant reading of gravity and pH .... 😄
 

pvtpublic

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If you don’t have an etched scale inside your kettle and don’t want to go to the trouble of etching it yourself, a stainless steel ruler is an easy way to measure volume and thus boil-off rate.
Thanks for bringing this up, I guess I take mine for granted enough to fail at mentioning it.
 

hotbeer

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If you know the pre-boil gravity and the starting volume in the kettle, then you should also know or be able to figure out what it is during the boil as the volume reduces.

You can do your figuring ahead of time and know what volume you need to be at to have the FG you desire. Then the stuff in the middle will be easy to figure as it's pretty linear I'd imagine.
 
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If you know the pre-boil gravity and the starting volume in the kettle, then you should also know or be able to figure out what it is during the boil as the volume reduces.
apologies if I missed (above) the idea that boiling water/wort takes up more space than chilled water.

When measuring volume (using a ruler or marks on the kettle), one needs to account for expansiom at higher temperatures. It's roughly 2% at 150F (mash temp) and 4% at 212 (boil temp).

@doug293cz posts a table periodically.
 

hotbeer

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Well if you cool something at the 5 gallon mark on your kettle from 210 to 68°F then you'll have all of about 2 cups difference.

Sure it makes a difference for the calculations, but I don't think you'd see the two cups on the side of the kettle.

While we can calculate stuff to the n'th degree, we can't easily brew or do other stuff to that degree.

It's not something I really want to argue. It's just a matter of whether the OP wants to really know the SG of their wort at every moment in time and collect a lot of what for me would be mostly useless data or whether they just want to know when their wort is close to the FG they desire.

The OP really didn't say if they absolutely required precision data every moment. So I was offering a there 'bouts method.
 

balrog

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Hello homebrewers,

I was wondering if anyone has tried any automated way of measuring gravity during boiling stage? I often have to do adjustments to my water level before I cool the wort for fermentation to get the right pre-fermentation gravity. I usually take a sample, cool it down to ~25 degrees and then use refractometer/hydrometer to check the gravity. Let me know if anyone has tried anything to measure this digitally or any other automated way?

Another thought: should you decide to boil as long as you want or need to get to a certain specific gravity with this theorized new method, what then happens to all your hop additions being calculated for how long they are in the boil?
 

RogerGrahl

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Another thought: should you decide to boil as long as you want or need to get to a certain specific gravity with this theorized new method, what then happens to all your hop additions being calculated for how long they are in the boil?
Bingo! Great observation. If you are boiling with an open kettle (no steam condensing lid), your boil off rate will vary due to the environment…air temperature, humidity, barometric pressure, wind. One way to nail your numbers is plan to add a quart of top up water at the end of the boil. That way you can boil to time and not mess up your hopping schedule. When the boil is complete, top up to your post boil volume. The top up may be more or less than the quart you planned. If your OG is off, adjust your efficiency for the next brew.
 

Brooothru

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My refractometer says it is temperature compensated. I grab a sample of boiling wort and put a couple drops onto the glass, close the cover and read the gravity immediately. I don't add adjustment water until the wort is chilled to pitching temp.
After using hydrometers (and thermometers) for more than 20 years to take and calculate gravity readings, I finally got a handheld refractometer. Figured it would be more accurate as well as easier to chill a much smaller sample. It would also be easier to read a refractive index than a liquid menicus.

That was mostly true, but still there were calculations required to convert to specific gravity and correct for temperature deviations as well as alcohol presence when fermentation began. Temperature compensating refractometers still required samples to be within a narrow range of about +/-10°F. Even my eventual digital automatic refractometer was subject to errors.

Totally agree with @McMullan (below) that EasyDens is what you're looking for if the cost doesn't cause heart palpitations. I picked up mine with a 15% promo from MoreBeer. Haven't looked back. Neat device.
 

seatazzz

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What was said above, a refractometer with ATC (automatic temperature compensation). I'm six years into this rabbit hole and still have too many variations in my boiloff rate. Refractometers can be had fairly cheap on Amazon; mine is over 3 years old and still works great, and as I recall was less than $20. Repetition also helps; for example, in my system (3-vessel), I know that if I start with 9 gallons preboil at 1.035 gravity, if I finish up at 6 gallons into the fermenter I'm going to get SG of about 1.055-1.060. Yes, that's a pretty big range, but if you read the BJCP guidelines, most beers have a fairly decent ABV range (FG-SG x 1.325=ABV% is a good basic calculator for final ABV).
 
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