Homebrewers Association | AHA Forum

General Category => General Homebrew Discussion => Topic started by: HoosierBrew on February 12, 2013, 02:26:01 PM

Title: Refactometer
Post by: HoosierBrew on February 12, 2013, 02:26:01 PM
Have a question regarding refractometers :

       I use mine along with a hydrometer for OG measurements.  I know that the alcohol present at FG makes it inaccurate, so I use the hydrometer for that. But I'm aware there are corrections that can be used for FG measurements.  Are the corrections reliable enough to make it worthwhile? It seems that abv% would have a direct relationship on a correction.  Thanks!
Title: Re: Refactometer
Post by: davidgzach on February 12, 2013, 02:33:55 PM
I looked at the calculations once and decided to just use my hydrometer for FG measurements.  YMMV.

Dave
Title: Re: Refactometer
Post by: blatz on February 12, 2013, 02:36:29 PM
the calculations are very worthwhile - sean (a10t2) has put together a spreadsheet which makes it very easy. http://seanterrill.com/2011/04/07/refractometer-fg-results/


the refractometer calculator in BeerSmith2 has also been very good to me (i.e. same as hydro) once I got the correction factor dialed in.

Title: Re: Refactometer
Post by: Slowbrew on February 12, 2013, 04:43:54 PM
I use Sean's spreadsheet and have very good luck with it.  I test it now and then by using a hydrometer to verify the calculations.  It is also close enough to trust in my brewery .

Paul
Title: Re: Refactometer
Post by: Hokerer on February 12, 2013, 05:00:13 PM
the calculations are very worthwhile - sean (a10t2) has put together a spreadsheet which makes it very easy. http://seanterrill.com/2011/04/07/refractometer-fg-results/

He's also got an online version, no spreadsheet necessary...

http://seanterrill.com/2012/01/06/refractometer-calculator/ (http://seanterrill.com/2012/01/06/refractometer-calculator/)
Title: Re: Refactometer
Post by: a10t2 on February 12, 2013, 07:26:31 PM
After deriving the equation, I solicited other brewers' data. I don't have the numbers on me, but six or seven people contributed 70 or so data points, and the standard deviation for those was 0.0013 - a little more than one "gravity point". So statistically speaking, you could expect the correlation to be within one point 56% of the time, two points 88% of the time, and four points >99% of the time.

I will say that in my own experience the standard deviation is a bit smaller than the overall sample. So when using consistently and thoroughly calibrated instruments, the calculation is about as precise, or even a bit more so, than a cheap hydrometer.
Title: Re: Refactometer
Post by: HoosierBrew on February 12, 2013, 07:29:02 PM
Thank you Sean !  That's more than reliable enough to start doing via your calculator. Appreciate it.
Title: Re: Refactometer
Post by: davidgzach on February 12, 2013, 08:09:30 PM
I'm going to give this a try.  Thanks for posting!

Dave
Title: Refactometer
Post by: majorvices on February 13, 2013, 12:13:28 AM
i've tried several conversion methods and I never got an accurate reading for FG.
Title: Re: Refactometer
Post by: jeremy0209 on February 13, 2013, 01:11:15 AM
i've tried several conversion methods and I never got an accurate reading for FG.
Yeah, I've never been able to get an accurate FG either, so I just use the hydrometer on the fermented side.  The refractometer sure is handy as hell for runnings gravity, preboil gravity, and OG, though.
Title: Re: Refactometer
Post by: oly on February 13, 2013, 07:40:31 AM
I use this calculator:  http://onebeer.net/refractometer.shtml

The several times I checked it with a hydrometer it was very close. Close enough  :)

But even given the inaccuracy of the refractometer FG measurement, I still think it's a great tool. After all, when I measure FG, I'm less concerned with the absolute accuracy of the FG reading, than I am in just monitoring fermentation completion.  Unless I've completely screwed something up (pitch rate, oxygenation, ferm temp), I know it's going to finish.  So pragmatically, the FG reading is just a reading of "how done is it", i.e. is it still dropping??   The refractometer is as good a monitor of this as is the hydrometer.  If I get a reading of 8 brix for 3 times over a week, I know it's done. Whether it's 1.012, 1.011, or 1.010, doesn't really matter.
Title: Refactometer
Post by: majorvices on February 13, 2013, 12:37:54 PM
My difference was always exceptional - like 8 points off or so. And I use the onebeer.net conversion as well. Not sure why it never worked for me.

Lately my refractometer has been giving me screwy reading on pre fermentation readings as well so I just use my hydrometer now for everything.
Title: Re: Refactometer
Post by: erockrph on February 13, 2013, 02:15:02 PM
My difference was always exceptional - like 8 points off or so. And I use the onebeer.net conversion as well. Not sure why it never worked for me.

Lately my refractometer has been giving me screwy reading on pre fermentation readings as well so I just use my hydrometer now for everything.

This seems obvious, but have you tried giving it a thorough cleaning?
Title: Refactometer
Post by: majorvices on February 13, 2013, 02:59:46 PM
It's as clean as it can be.
Title: Re: Refactometer
Post by: ynotbrusum on February 14, 2013, 01:07:09 PM
Major- was the refractometer also off on the OG?  I calibrate mine using distiller water, so I don't know how one could calibrate it differently for FG to know it is spot on without using a hydrometer, like Sean did.  I posted elsewhere that my lab grade FG hydrometer recently broke, which is a pain, because my cheaper ones are so hard to accurately read, that I was thinking of going to refractometer readings for both ends.  Your post has me wondering...maybe I will do both for the next few batches and see if they correlate well enough to use the refractometer with Sean's adjustment spreadsheet.  I don't brew a lot of high gravity beers, so it may not be significant differences for me....

Thanks for the insight.
Title: Refactometer
Post by: majorvices on February 14, 2013, 02:01:15 PM
Mine seems to just give screwy readings on the OG. If I take 3 readings sometimes all three will be different. I know some have attributed this to wort temperature (though mine is supposedly ATC) but even if I cool the sample first it will give me a different reading than my hydrometer. I'm on my second refractometer (dropped the first one) and both of them gave me problems like this, though the first seemed more accurate. The second one does not read the same as my hydrometer.

I have calibrated it with distilled water and or tap water (I don't think the differences between the two calibration solutions are exceptional enough to throw a reading off as much as I am seeing).

Bottom, line is, I just feel more comfortable in the reading I get from my hydrometer.
Title: Re: Refactometer
Post by: denny on February 14, 2013, 04:58:55 PM
My difference was always exceptional - like 8 points off or so. And I use the onebeer.net conversion as well. Not sure why it never worked for me.

Lately my refractometer has been giving me screwy reading on pre fermentation readings as well so I just use my hydrometer now for everything.

Same here.  I have 2 refractometers and they read different from each other and both are different than my hydrometer.  I've gone back to hydrometer for everything.
Title: Re: Refactometer
Post by: coastsidemike on February 14, 2013, 05:41:01 PM
My difference was always exceptional - like 8 points off or so. And I use the onebeer.net conversion as well. Not sure why it never worked for me.

Lately my refractometer has been giving me screwy reading on pre fermentation readings as well so I just use my hydrometer now for everything.

Same here.  I have 2 refractometers and they read different from each other and both are different than my hydrometer.  I've gone back to hydrometer for everything.

Good info.  Does calibrating have any affect?
Title: Re: Refactometer
Post by: denny on February 14, 2013, 05:44:10 PM
Good info.  Does calibrating have any affect?

Nope, not really.
Title: Re: Refactometer
Post by: bluesman on February 14, 2013, 05:54:56 PM
I use my refractometer for measuring pre-boil/boil gravity only. I typically get pretty consistent readings (+/- 0.2° Plato). I still use a hydrometer to measure chilled wort (OG). The prism on the refractometer must be kept clean and dry for accurate readings. Calibration is also recommended every so often. Keep in mind that boiling wort sampling requires an agile/quick transfer time to avoid evaporation losses. In other words the wort sample must be transferred from the kettle to the prism "quickly" in an effort to avoid evaporation loss during the transfer process. Once the hot wort sample is on the prism and the daylight plate is closed, I allow about a minute for the temperature to stabilize then record the measurement.
Title: Re: Refactometer
Post by: blatz on February 14, 2013, 07:27:42 PM
My difference was always exceptional - like 8 points off or so. And I use the onebeer.net conversion as well. Not sure why it never worked for me.

Lately my refractometer has been giving me screwy reading on pre fermentation readings as well so I just use my hydrometer now for everything.

Same here.  I have 2 refractometers and they read different from each other and both are different than my hydrometer.  I've gone back to hydrometer for everything.

this may sound dumb, but you aren't looking at it through your glasses are you?  I've compared at least 3-4 refractos to mine (at club brews and such) and they've always been close, usually off due to calibration.
Title: Re: Refactometer
Post by: a10t2 on February 14, 2013, 08:04:52 PM
If you guys want to bring your refractometers to NHC, we can do lessons. ;D
Title: Refactometer
Post by: majorvices on February 14, 2013, 08:05:21 PM
No, but I may be looking through the wrong end. :P I don't wear glasses or contacts.
Title: Re: Refactometer
Post by: tygo on February 15, 2013, 12:19:14 AM
As long as I calibrate mine at the temp I'll be using it, don't use it outside when it's extremely cold or hot, and adjust for the difference between sucrose and maltose, mine usually reads within a couple of points of my hydrometer.  I've been using it pretty much exclusively on the hot side for awhile now.
Title: Refactometer
Post by: majorvices on February 15, 2013, 01:01:55 AM
As long as I calibrate mine at the temp I'll be using it, don't use it outside when it's extremely cold or hot, and adjust for the difference between sucrose and maltose, mine usually reads within a couple of points of my hydrometer.  I've been using it pretty much exclusively on the hot side for awhile now.

Hmmmmmm ..... there's a thought right there. I might check into that. But I thought the great thing about a refracto is that you can get a fairly instant reading right out of the kettle. If I have to cool the samples and the calibration down to the same temps it stops making it worth it. I can get my hydrometer sample cooled down in under 10 minutes.
Title: Re: Refactometer
Post by: tygo on February 15, 2013, 01:10:30 AM
I was referring to the ambient temp/temp of the refractometer, not the sample.  I don't cool the sample.  But if the ambient temps are too extreme and if I let the refractometer sit out in those temps, calibrate there, and use it, my readings are inaccurate. 

Case in point the last two weekends when it was 35F in the garage where I brew.  I left the refractometer in the laundry room right inside the door where it's normal room temp and I was good to go.  I get the same type of inaccuracies in the summer when its' 110 in the garage.
Title: Re: Refactometer
Post by: euge on February 15, 2013, 01:27:45 AM
WTF is a "Refactometer"?
Title: Re: Refactometer
Post by: a10t2 on February 15, 2013, 01:32:00 AM
WTF is a "Refactometer"?

It's a device for measuring how many times people repeat trivia.
Title: Refactometer
Post by: majorvices on February 15, 2013, 02:02:23 AM
WTF is a "Refactometer"?

It's a device for measuring how many times people repeat trivia.

I just scrolled through every post to see if I misspelled "refractometer" ....
Title: Refactometer
Post by: bluesman on February 15, 2013, 02:40:15 AM
WTF is a "Refactometer"?

It's a device for measuring how many times people repeat trivia.

Now that's some real beer geek comedy genius right there hombre. :))
Title: Re: Refactometer
Post by: Wort-H.O.G. on February 15, 2013, 04:26:58 PM
I must say that IME, refractometer is great for the mash- assuming you calibrate it with your hydrometer.

Beyond that, i just use it as a quick and easy point of reference to where my beer is at or where my starter is at. No two readings are them same with fermented wort, and haven't found any refractometer spreadsheet or calculator that provides the same adjusted gravity reading.
Title: Refactometer
Post by: denny on February 15, 2013, 04:42:21 PM
My difference was always exceptional - like 8 points off or so. And I use the onebeer.net conversion as well. Not sure why it never worked for me.

Lately my refractometer has been giving me screwy reading on pre fermentation readings as well so I just use my hydrometer now for everything.

Same here.  I have 2 refractometers and they read different from each other and both are different than my hydrometer.  I've gone back to hydrometer for everything.

this may sound dumb, but you aren't looking at it through your glasses are you?  I've compared at least 3-4 refractos to mine (at club brews and such) and they've always been close, usually off due to calibration.

Both with and without, makes no difference.