Refractometer Issues

[RobW]

I bought a refractometer on Ebay recently and calibrated it before use.
First time out it showed an OG of 13 Brix which was about where I was aiming (1052)
After primary fermentation SG was 6 Brix (about 1024) which surprised me because I was using Nottingham and it had fermented strongly.
I checked using the hydrometer and it showed 1008 which was more like I'd expect.
The beer tastes OK and I'm confident the hydro reading is the correct one but I'm a bit confused why the OG and zero levels should be OK (although I didn't check the OG against the hydro) but the FG is way off.

Anybody have an explanation or had a similiar issue? Apart from it's a cheap piece of crap and I should have saved my money? <_<

edit: typo

 

[andrewg1978]

I had the same prob. From what was explained to me light refacts at a different rate through alcohol, but I'm not able to explain how to "Adjust your reading".

 

[Cortez The Killer]

Are you using the correcting formula for Brix during fermentation ?

See here http://www.mtbrewing.com/calculator-refractometer-converter/

Cheers

 

[Kleiny]

refractometer test the level of suger in a solution so at OG it works fine
after fermentation because of the alcohol present it will not show a true reading although i have found that the reading resembles the alcohol % so if it reads 6 Brix then it is around 6 %

kleiny

 

[Stuster]

Yep, as Andrew says, the alcohol in fermenting/fermented wort will throw out the readings. You can use the refractometer, you just need to use a correction formula. Beersmith and Promash both have one and I'm sure there are plenty out there on the internet. Personally, I'd just download one of the trials of those programs.

Edit: Using Beersmith, that refract reading translates to a FG of 1006 which is pretty close to your hydro reading.

 

[RobW]

Are you using the correcting formula for Brix during fermentation ?

See here http://www.mtbrewing.com/calculator-refractometer-converter/

Cheers

Yep

 

[RobW]

Didn't know about the alcohol affecting the FG reading. That helps make sense of it.
Will go and play with Promash.

Thanks fellers.

 

[drsmurto]

You can calibrate your refractometer so you never need to use a hydro again (except as an excuse to taste samples...) by doing a recording using both the refract and the hydro of a fermented wort. You enter that into beersmith and it then has a correction factor.

I was a bit dubious at first so kept checking with the hydro for another 3 brews but it was spot on every time.

 

[andrewg1978]

refractometer test the level of suger in a solution so at OG it works fine
after fermentation because of the alcohol present it will not show a true reading although i have found that the reading resembles the alcohol % so if it reads 6 Brix then it is around 6 %

kleiny

Interesting observation, has anyone else had similar?

This would make it a lot eaiser then trying to adjust.

The other thought i had over a couple of quite brews on sat was to Calibarate the rafratometer using a known end eg 1008. then measure standard water. The difference should give you a fermented calibration level. Might be eaiser then trying to use a formular every time?

<_< Also assuming using similar ingredience each time as well. Eg kit +BE2, if +- malt level you may have to have different offsets for different types of brews.

Sorry about the rambles!

 

[Stuster]

That 6 Brix to 6% calculation won't work in most cases. Using a brewing program, the calculation is dead easy.

 

[andrewg1978]

You can calibrate your refractometer so you never need to use a hydro again (except as an excuse to taste samples...) by doing a recording using both the refract and the hydro of a fermented wort. You enter that into beersmith and it then has a correction factor.

I was a bit dubious at first so kept checking with the hydro for another 3 brews but it was spot on every time.

Great minds think alike! hows that both put the same in within a few sec. i unfortunately was unable to test my theory over the weekend as my darling wife smashed my hydrometer in the sink fri night :angry:

 

[drsmurto]

Not sure how much use this is to anyone but the correction factor i have in beersmith is 1.0145. Punch that into your setup and see if you get a number that makes sense.

Yes, i realise everyone needs to calibrate their own individual refracts but at a pinch this might do temporarily.

 

[lokpikn]

View attachment Refractometer_Chart___During_Fermentation___Brix_to_SG.xls

If this attacment works this is what i use during fermentation.

I forgot who I got it from but it was from AHB. Thanks

 

[RobW]

View attachment 19232

If this attacment works this is what i use during fermentation.

I forgot who I got it from but it was from AHB. Thanks

and fits my readings exactly: OG 1052, SG 1008 = 6 Brix

beautiful B)

 

[Guest Lurker]

Seems to me its actually the other way around. The refractometer is not affected by the presence of alcohol, the hydrometer is. If it wasnt for the fact that everyone is so used to seeing apparent attenuation as measured by the hydrometer, it would be better to think in real attenuation and correct the hydro.

 

[alexbrand]

Check this tool. Still in developement. I haven't yet found all English expressions in my dictionary.

View attachment RefractorBETA.zip

Alex

EDIT: Some basics on how a refratometer works you can find on wikipedia. Alcohol affects refraction other than sugar. This is the reason why you must "interprete" the measured value.

 

[pint of lager]

Your og sample is easy to deal with, it is a mixture of water and malt sugars.

Alcohol content affects both the refractive index and the density, so both the refractometer and hydrometer readings will be skewed once you start taking readings after pitching. Neither will give the correct answer.

You could always go all white coat, grab a known volume of wort in a beaker, simmer gently to evaporate the alcohol, then top up with distilled water back to your known volume, stir well, cool and then do a refractometer sample and a hydrometer sample.

 

[BenH]

You could always go all white coat, grab a known volume of wort in a beaker, simmer gently to evaporate the alcohol, then top up with distilled water back to your known volume, stir well, cool and then do a refractometer sample and a hydrometer sample.

Yikes!

Or you could just believe the experts and use the calculators which are readily available. (I know which choice I've made! )

 

[Pumpy]

Refractomers beat me sometimes they work sometimes they dont .

If it dont give me the reading i want i check with a hydrometer

pumpy .

 

[Kai]

Seems to me its actually the other way around. The refractometer is not affected by the presence of alcohol, the hydrometer is. If it wasnt for the fact that everyone is so used to seeing apparent attenuation as measured by the hydrometer, it would be better to think in real attenuation and correct the hydro.

I'm pretty sure refractometer readings are still affected by the presence of alcohol but I'm not sure by how much. Try measuring some vodka or metho sometime to see. Or, spike a wort sample with metho and see what happens.