Understanding abv calculators.

[bike2brew]

you would think, I have seen side by side comparisons using tilt, hydrometer and refractometer and the tilt was the most reliable. Remember you need to adjust for temperature. And for the self correcting devices, they correct less effectively the further they move along the temp range for which they were designed. Also, you need to calibrate your devices.



lastly, it's all irrelevant anyway. IMO, most readings from home brewers are inaccurate (just take a look at how many post on the subject don't read a hydrometers meniscus correctly ). Unless you are dealing with a stuck fermentation or dialing in some advanced fermentation techniques, and you know exactly what pH and ions were on your water, the numbers aren't really going to make much of a difference. You'll still drink and enjoy your beer, and you'll likely never be able to tell by taste if your beer was a few points off (and perhaps even better than designed.

Fwiw (I have an iSpindel). If you calibrate your Tilt correctly. and it doesn't get stuck on Krause, it's nice to know when fermentation is leveled off without having to let O2 get to your beer. My refractometer lets me take quick reading but I only care about being in the ballpark. And my hydrometer is useful for double checking the other two (when I talk the time to cool wort/beer down to 60°

Keep leaning about gravity reading techniques and devices. It's good to know, and reducing user error will make your day more relaxing.

RDWHHB

+1, They are estimates subject to instrument and random error. If you want to really geek out, take multiple measurements with each device, calculate means, standard error, and 95% confidence intervals. Too much fun and supports an illusion that you are a brewery scientist.

 

[AZ Maverick]

I guess I'll throw in my .02 -
I use my cheap ATC refractometer and Tilt hydrometer only for brewing all of my beers.
After learning how to properly use them, the refractometer and Tilt hydrometer readings are so close to my standard triple scale glass hydrometer that the difference is just noise.
I haven't used my triple scale hydrometer in years.
I use my refractometer during the initial brewing process for pre-boil and OG and the readings usually agree with BeerSmith unless I've done something wrong.
My Tilt OG agrees with my refractometer and is greatest thing going for keeping tabs during the fermentation process (especially lagers).
When Tilt says I've hit FG, I'll still let it sit for a few weeks before I crash and keg, and while kegging I'll take one last refractometer reading to make sure it agrees with Tilt and BeerSmith expected readings.
I never use the SG reading on the refractometer, only the Brix - and I use the BrewersFriend refractometer calculator (with a 1.04 WCF) to convert the readings.
I also did a manual 3-point calibrations on my two Tilt hydrometers.

 

[sodbuster]

OK side by side comparison the refractometer was reading 1.027 and the hydrometer read 1.025

 

[bike2brew]

Again, they are estimates. Take several readings, average, calculate standard deviation and look for statitistical difference. 2/100's of a point is not likely to be statisitically significant. How does the beer taste?

 

[sodbuster]

Some are better than others but they are all really good.

 

[sodbuster]

I think I promised a follow up, upstream. Following through on that.

 

[bracconiere]

OK side by side comparison the refractometer was reading 1.027 and the hydrometer read 1.025

this seems really weird, you said you had a OG of 1.065, right?

edit: i'm just saying aparently this liquid doesn't have much alcohol......

and that "corrected gravity" if what the OG would have been....

 

[sodbuster]

That’s is a cool calculator where did you find it @bracconiere? The refractometer reading OG was 15.9b and the hydrometer finished gravity was 1.025

 

[dmtaylor]

Your readings cannot possibly all be correct. Have you calibrated your hydrometer and refractometer in plain room temperature water? Something isn't right.

 

[sodbuster]

Why?

 

[dmtaylor]

You've provided an original refractometer reading of 15.9 Brix, final refractometer of "1.027", and final hydrometer of 1.025.

My understanding is that you used US-05 yeast. Unless your recipe was extremely wonky, typically this yeast attenuates to a percentage in the mid-80s, with an average of about 83%.

Assuming your original Brix of 15.9 Brix is accurate, which equates to 1.065 OG, you should end up with FG of approximately 1.011 on a hydrometer, or a final Brix reading of about 7.0, to equate to the 1.011, based on the following calculator:

http://seanterrill.com/2012/01/06/refractometer-calculator/

Your reading of 1.025 is nowhere near 1.011. Could be a recipe problem. However I think it's an error of how the readings are taken, and here's why.

I keep putting the "1.027" in quotation marks because a refractometer does not measure in specific gravity units, and ESPECIALLY should not be reported as such when alcohol is present. If you are still using the SG scale on your refractometer, please don't. Take all refractometer measurements in Brix.

Based on the "1.027", my GUESS is that your actual final Brix reading would be about 6.4. This would equate to a final gravity of 1.009. If I am correct, THAT would be pretty close to the expected FG of 1.011 from US-05. (You did use US-05, did you not?) See this:

Finally, I think your hydrometer might be broken. Under normal circumstances, a hydrometer should always be more accurate than a refractometer. However, there's just no way I can see that the FG can be 1.025, given your refractometer readings of 15.9 Brix and "1.027", and assuming your recipe and brewing technique aren't crap.

So, this is the long and complicated answer for why I said "your readings cannot possibly all be correct". It's just not possible.

 

[sodbuster]

@dmtaylor thank you for helping me work through this. I just got the hydrometer and apparently I was reading it wrong, basically reading the scale backwards for some reason. What I thought was 1.025 was actually 1.015.

 

[dmtaylor]

@dmtaylor thank you for helping me work through this. I just got the hydrometer and apparently I was reading it wrong, basically reading the scale backwards for some reason. What I thought was 1.025 was actually 1.015.

Oh, okay. That makes a bit more sense. Refractometers aren't super accurate when alcohol is present, so I would trust the hydrometer more than the refrac. Your 1.015 is reasonably close to the 1.011 that I would have expected.

Still I wonder whether your hydrometer is reading accurately. They are often inaccurate by a couple points. Have you checked your hydrometer in plain water? For example (and who knows if this is true until you check!), it should read 1.000 in plain water, but I wonder if it will read 1.002, to where you would need to subtract 2 points from every reading so your true OG and FG readings would actually be like 1.063 and 1.013, instead of 1.065 and 1.015. If true, this would be even MORE in line with my expectations of ending up closer to 1.011.

 

[sodbuster]

@dmtaylor I just checked it and its dead on. I started drilling down on this topic so I could use it more as a diagnostic tool than a abv indicator. When I mash I use 1.5 quarts per pound at 173 degrees, after stirring it the mash will settle in at 152. I wonder if I should mash closer to 148. Does the short time it takes to cool hurt me as well?

 

[dmtaylor]

@dmtaylor I just checked it and its dead on. I started drilling down on this topic so I could use it more as a diagnostic tool than a abv indicator. When I mash I use 1.5 quarts per pound at 173 degrees, after stirring it the mash will settle in at 152. I wonder if I should mash closer to 148. Does the short time it takes to cool hurt me as well?

Great to hear that your hydrometer is dead-nuts.

As long as you are stirring well, you should be able to keep on doing what you have been doing with minimal enzyme loss. A mash temp of 152 F is very reasonable, but if in your experience you want higher fermentability / lower FG / higher ABV, then go ahead and mash your recipes a little lower at 147-148 F, that should help.

 

[sodbuster]

thanks @dmtaylor

 

[sodbuster]

 

[sodbuster]

Fwiw the refractometer read 1.0325. This for the person who asked up stream

 

[dmtaylor]

Heh... looks like 1.011, as a wise man once predicted.