hydrometer vs refractometer

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Martinez

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Hey guys, feeling pretty dumb here that I can't read my instruments correctly. hah

Post boil my refractometer reading was ~13 to 14 = 1.055. Today, after couple weeks fermenting, it read a bit above 6 Brix. Using the calculator in brewers friend, it said that the 6 brix (which would be about 1.025) actually represents close to 1.005 if you account for the starting gravity. This would indicate my beer is ready. Target was 1.050 start and 1.003 end.

I added 100ml to a hydrometer as well, though, and it read 1.010 to 1.015 give or take. Which would imply my beer is definitely not ready.

I lowered my fermenter pressure to about 1psi and let it spunding at that pressure for a few hours to stabilize. Increased the valve to a 15psi spunding pressure to see if pressure was still building up and it seems to be increasing extremely slowly now... which to me would also indicate fermentation is finished and likely just diluted co2 stabilizing in the headspace.

Do I need to correct a hydrometer reading to account for alcohol as well?
Help pls :)
 

philrob

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Hi Martinez,
Yes, you do need to allow for alcohol as well.
Lots of brewing software will help you with that, for example Beersmith3 etc, but I also have a chart here which might be easier for you.
Hope it helps.

Refractometer_Calculations.jpg
 

Martinez

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Ok, so if my original 1.055 is actually correct, then my final 1.010-1.015 is definitely wrong, otherwise i'd be well bellow 1.000 hahhaha
Even if it was actually 1.025 (the 6 Brix that I measured on the refractometer) and I accidentally read it wrong in the hydrometer, it'd at 1.005 territory (which incidentally is the same as I got out of the calculator).

I'll start cold crashing then :D

Cheers
 

MHB

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Why the hahaha? Plenty of dry and extra dry beers finish under 1.000.
The reading of 1.000 only means the density is the same as water. If you had 1L of 1.015 beer it would weigh 1.015kg.
Alcohol is less dense than water so if you make a highly fermentable wort it’s quite possible to get FG's under 1.000.
I have seen several beers in the 0.955-1.000 range. Not my cup of tea but it can happen.
Mark
 

Martinez

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Well, it was expected to finish at 1.003, so perhaps it could go below.
Either way, should be fine to cold crash, right?
 

duncbrewer

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You say reading 13 or 14 post boil.
Is this from the fermenter or a sample taken hot?
You would need to cool that post boil reading for your refractometer, did you not have a hydrometer reading for OG?

I'd go with the hydrometer reading corrected for temperature and making sure no bubbles on the hydrometer.

Not sure why you can't read the hydrometer more accurately than " it read 1.010 to 1.015 give or take ".

With that level of accuracy it's going to be tricky getting consistency.
 

Martinez

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Both hydrometer and refractometer measures 1.000 at water.

The reason for the range is because I don't remember what I measured and I didn't write it down 😬
But definitely the issue was with correction for OG.

My OG measure was out of boil, so definitely wasn't at the right temperature.
 

MHB

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The old Precision and Accuracy question!
There are lots of ways to measure wort and beer, I mostly use a digital refractometer pre-fermenter as its quick and accurate with ATC (Automatic Temperature Compensation) like most refractometers'; the sample size is measured in drops so they reach ambient very quickly.
A digital refractometer will usually give results at 0.1oP or 0.0004 SG. Hydrometers and refractometers are available in a bunch of ranges and precisions. A decent general purpose Hydrometer (1.000-1.100 SG) is usually marked in 0.002 increments (one fifth as accurate as my digi-refrac). You can get narrow range hydrometers, picked up a couple of old Carlton hydrometers that are only 5 Brix (Plato) on a 300mm long hydrometer, they are called terminal gravity hydrometers (F.G.) and are marked in 0.1 Brix/Plato.
The more accurate an hydrometer the more care must be taken with temperature correction. Have got a box set, Hydrometer, test tube and thermometer, need them all.
Plenty of the inexpensive hand held refractometers are only good to 1oP(Brix) some even that is hard to read. Top end is Lab ones that look like a microscope, have heated stages to keep the sample at exactly the right temperature and cost about as much as a car...
It’s worth having a look at what your various instruments can accurately report. Remember to that you are at the mercy of your least accurate reading. Before you use the numbers in any calculations.
 
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cb341982

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The old Precision and Accuracy question!
There are lots of ways to measure wort and beer, I mostly use a digital refractometer pre-fermenter as its quick and accurate with ATC (Automatic Temperature Compensation) like most refractometers'; the sample size is measured in drops so they reach ambient very quickly.
A digital refractometer will usually give results at 0.1oP or 0.0004 SG. Hydrometers and refractometers are available in a bunch of ranges and precisions. A decent general purpose Hydrometer (0.000-1.100 SG) is usually marked in 0.002 increments (one fifth as accurate as my digi-refrac). You can get narrow range hydrometers, picked up a couple of old Carlton hydrometers that are only 5 Brix (Plato) on a 300mm long hydrometer, they are called terminal gravity hydrometers (F.G.) and are marked in 0.1 Brix/Plato.
The more accurate an hydrometer the more care must be taken with temperature correction. Have got a box set, Hydrometer, test tube and thermometer, need them all.
Plenty of the inexpensive hand held refractometers are only good to 1oP(Brix) some even that is hard to read. Top end is Lab ones that look like a microscope, have heated stages to keep the sample at exactly the right temperature and cost about as much as a car...
It’s worth having a look at what your various instruments can accurately report. Remember to that you are at the mercy of your least accurate reading. Before you use the neumbers in any calculations.

Sorry to sidetrack the thread, but do you have a recommendation for a digital refractometer?
 

MHB

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There are a bunch on the market, I would look at a midrange instrument, Hanna and Milwaukee both have good units.
There are a new family of SG meters hitting the market that are in effect phone accessories Anton Par have one and no doubt many others.
These work by drawing a small sample into a U-tube, plucking it and listening to the frequency which is converted into density. Works in both wort and the ferment, being phone app driven they are a lot cheaper than the stand alone versions which cost up to $4k.
Worth taking a look at, if I were replacing my digital refrac I would be very tempted.
Mark
 

duncbrewer

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I bought a Milwaukee digital refractometer, have to say works brilliantly, free postage from the USA. It also calculates potential alcohol, which is really a complete waste of time as it assumes that you are fermenting wine so gives you a figure based on it's assumption of your final gravity. I take more readings now than I did in the hydrometer days.
It was about half the price of the EasyDens from Anton Paar. Guess the Refractometer will last a long time. Perhaps not as long as my hydrometer which was sold by Boots the Chemist in the UK pre decimal so around 1970.
 

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