Gravity readings: hydrometer and refractometer confusion

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Anglecard48

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Hello. I just signed up at HomeBrewTalk. This is my first post. If I'm not in the correct forum, I apologize.

I have an Amber Ale in secondary with target FG 1.013 according to the recipe (American Amber Ale, Zainasheff and Palmer).

After four weeks in the fermenter, I have a FG reading of 1.024 on my refractometer. However, The it measures 1.005 in my hydrometer. I did recalibrate my refractometer and got same reading. So my refractometer tells me I'm 11 points too high and my refractometer tells me I'm 8 points too low. My OG was 1.052 -- right on the money.

It's been a month in the fermenter, in a fridge at 68 degrees (Safale 05 yeast). Throughout the ferment / conditioning I had only taken refractometer readings — not hydrometer readings. At three weeks I read 1.024 SG on my refractometer and so, I swirled up the beer, the stuff that had sunk to the bottom of my fermenter, and gave it another week at 71 degrees. After the additional week, no change in refractometer OG.

Being curious, I pulled my hydrometer off the shelf and took a reading. Confusion followed.

But, the beer tastes good so I think I'll go ahead and bottle it.

I've recently been attempting to pay attention to specific gravities after suffering from inconsistent brews. I bought the refractometer to make it easier to get readings and drawing off less beer.

What should I think?
 

dmtaylor

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Welcome to the forum!

A refractometer requires adjustment whenever alcohol is present. Use a tool like one of these:



By the way... US-05 is a very high attenuating yeast. I would not have expected 1.013 but rather about 1.008 with that yeast. It is NOT equivalent to WLP001 or Wyeast 1056, despite what a thousand sources will tell you. Each of these three are unique, and have strayed significantly from one another genetically.
 
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seilenos

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I have an Amber Ale in secondary with target FG 1.013 according to the recipe (American Amber Ale, Zainasheff and Palmer).

After four weeks in the fermenter, I have a FG reading of 1.024 on my refractometer. However, The it measures 1.005 in my hydrometer. I did recalibrate my refractometer and got same reading. So my refractometer tells me I'm 11 points too high and my refractometer tells me I'm 8 points too low. My OG was 1.052 -- right on the money.

What should I think?

Rough calculations from your post:

OG of 1.052 is ~12.9 Brix.
FG of 1.024 is ~6.1 Brix.
(Brix Conversion Calculator)

Using the Refractometer calculator from the same site you get a corrected FG of 1.008.

There's some "slop" in using a refractometer for both OG and FG.
It would be better to use the Brix readings directly from your refractometer instead of converting OG/FG gravity points.

It is personal preference if you want to consider it "good enough".
 

AlexKay

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This is the old "make one measurement and you have an answer; make two and you have a problem." As folks point out, the refractometer won't give the correct gravity without a formula that corrects for the presence of alcohol. Since your numbers are reasonably close after that correction, I'd call it good.

Which one is correct? Could be one, could be neither. Folks seem to forget that in order to calculate ABV from hydrometer readings you have to (1) pick one from several choices of formulas that (2) correct for the presence of ethanol and (3) make assumptions about wort sugar composition. In other words, same as for a refractometer.

Pick one method -- whichever one you like, really, though I'll point out there isn't a "how many refractometers have you broken so far" thread -- and return to it to gauge reproducibility of your recipes. If you were selling the beer in the US, you don't need to get better than +/-0.3% accuracy. That's pretty much the accuracy we're talking about with the difference between 1.008 and 1.005.
 

hotbeer

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Make certain that none of the CO2 in your beer is forming bubbles on your hydrometer bulb when you take a reading. Usually spinning the hydrometer back and forth between your fingers shakes them off.

Bubbles sticking to the bulb will lift it higher and give a low reading.


I only use a hydrometer. Everything about beer is tabulated for what a hydrometer will show. Not much for how light is refracted through a prism and lenses.
 
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Anglecard48

Anglecard48

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Huge thanks to all of you for your comments. I need to do some book learning on specific gravity, how to measure it, how to interpret the measures, and how to make sure it's within margin of error.

I could not figure out the Sean Terrill or the Brewer's Friend calculators. I didn't know there was that kind of difference between Safale 05, WLP001 and Wyeast 1056. I don't know how to understand Brix readings. I don't know that I got the bubbles off of my hydrometer.

So I have some work to do to understand this. No offense to John Palmer, Charlie Papazian, Dave Miller, and Byron Burch (may he rest in peace) but those authors don't seem to provide much enlightenment on this topic. At least not that I have read.

So, I will believe that my current FG is 1.008 and will bottle tomorrow. I look forward to drinking it.

I see that there is some literature online on this topic by a guy name Brad Smith and a fellow named Kay Witkiewicz, which I will read. I will revisit the Sean Terrill and the Brewer's Friend calculators to see if I can understand them.

Please let me know if there are other good sources to refer to. I need to understand this.

I will boil up the exact same Amber Ale this week and get it pitched and into the fermenter. Hopefully I'll get better at understanding and controlling the gravity readings. So I can attain some consistency in my product.

Again, huge thanks to all of you.
 

RM-MN

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I have an Amber Ale in secondary with target FG 1.013 according to the recipe (American Amber Ale, Zainasheff and Palmer).

After four weeks in the fermenter, I have a FG reading of 1.024 on my refractometer. However, The it measures 1.005 in my hydrometer. I did recalibrate my refractometer and got same reading. So my refractometer tells me I'm 11 points too high and my refractometer tells me I'm 8 points too low. My OG was 1.052 -- right on the money.
The recipe tells you what someone else did or in this case, what final gravity they achieved. Your hydrometer tells you what final gravity the yeast and fermentation conditions caused.

The refractometer is a wonderful tool to use with all grain to see how the mash is progressing without having to wait to get a sample cool enough to use the hydrometer but the presence of alcohol distorts the refraction so using it for final gravity requires the correction factor. Since at the end of fermentation the beer will be near the proper temperature for the hydrometer which needs no correction I encourage that instrument for final gravity. The exception to this advice is for small batches where the hydrometer sample would comprise a higher percentage of the batch.

All recipe calculators I am familiar with will estimate the final gravity. Consider this to be just an estimation and don't get excited because what your hydrometer reads is different.
 
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The exception to this advice is for small batches where the hydrometer sample would comprise a higher percentage of the batch.
With small batches, one can choose to measure yield (bottles packaged) rather than "percentage of beer needed for hydrometer samples".

Scale the recipe to yield a 24-pack (a 12-pack, a 6-pack, even a single 7 oz bottle ;)) and include additional wort for hydrometer samples.
 
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