Refractometer Calculations - am I doing this right?

[Jim]

I'm using this calculator to try to work out my final gravity. OG was 1.052 (13 Brix on my refractometer's scale) and current reading is about 6.5 Brix.

I've mucked with the fiddle factor (called 'wort correction factor') so that the Brix for my original SG reading (which was confirmed with a hydrometer) matched the calculated original gravity of 1.052.

This is what it says: -

Input:
Original Bx = 13, Final Bx = 6.5, Wort Correction Factor 1.010 (replacing the default of 1.040)

Results:
Original Gravity: 1.0521 (12.87°P)
Estimated Final Gravity: 1.0122 (3.13°P)
Alcohol by Volume: 5.1% (4.1% ABW)

This would be ideal, only my hydro is reading about 1.016 - there's a lot of yeast in the sample though, which may be confusing it. The wort doesn't taste sweet.

[boingy]

I gave up trying to use my refractometer after fermentation started. I normally wait until I think it's done then take a hydro jar sample (and drink the beer afterwards). It usually only needs that one sample. If it is within a point or two of my target I keg it and it's fine.

[edonald774]

I use the calculators available on software like beersmith or http://www.northernbrewer.com/refractometer-calculator/

OG:13
FG: 6.5 corrected 2.3
ABV: 5.8%

[Goulders]

As Aleman's has pointed out the calculators aren't accurate for all Refractometers and you need to check over a few brews. Have you looked at the Sean Tyrill(?) website? I checked the FG using my Refractometer on my last brew and the 1.04 fudge factor didn't work. The correction factor was 1.08 I think

[Charles1968]

Check your hydrometer in water at 20 Celsius and make sure it's exactly 1.000. If not, that needs a fiddle factor too. You can also check your refractometer: 10 grams of white sugar FULLY dissolved in 90 grams of water at 20 Celsius is 10 degrees Brix (ie 10% sugar) by definition (and should read 1.040 on hydrometer). Keeping your refractometer's prism at 20 Celsius is important when you use it. Suspended yeast wont affect a hydrometer reading but CO2 bubbles collecting on the hydrometer can give a slight overestimate of gravity.

[Jim]

Thanks for the advice chaps. I will do a proper calibration of all my devices at some point.

I'm trusting my hydrometer here as I know how it behaves, but I'm playing about with the refractometer to see how it performs as well.

[Jim]

Did a bit more measuring today.

Calibration:
Plain Water at 20C - Hydro 1.000, Refractometer (zeroed using adjuster).

Sugar solution 10g + 90g plain water - Hydro 1.039, Refractometer 10Bx, 1.040 (i.e spot on)

Measurements
Fermented wort at 20C - Hydro 1.016 (i.e. hasn't budged), Refractometer 7.4Bx (equivalent to 1.029)

Correcting that reading using Sean Terrill's calculator with WCF of 1.020 gives: 3.92Bx (equivalent to 1.015) which agrees pretty well with the hydrometer.

I'm happier with my readings as last week the shadow line on the refracto was quite blurred (probably due to the vast amount of yeast in suspension). It also seems that the beer has finished primary so I'm turning the temperature down to give it a chance to clear before racking.

[BarnsleyBrewer]

Are these refractometers a good thing to use or just an added unnecessary complication?? I get by using an hydrometer like most breweries do without any problems?

[Jim]

Are these refractometers a good thing to use or just an added unnecessary complication?? I get by using an hydrometer like most breweries do without any problems?

Before the yeast goes in they are a huge advantage; at least they are if you're a grain brewer where you have to measure hot liquids frequently - it's a lot easier to cool a few drops of liquid down than 100ml or so, and you get a direct reading without having to use (e.g.) a hydrometer temperature correction table.

Once there's alcohol around they aren't so good - you need to do complex calculations to get the true reading, and even then, can you rely on it when you're going to bottle?

[BlackRocksBrewery]

Jim

I love the refractometer when sparging as I know when I can stop. This has improved my extraction efficiency and it is a real aid to my brewing. However, contrary to many more experienced brewers, I use a hydrometer in the FV to determine FG. I do sterilise the hydrometer.

S

[Aleman]

Can you rely on it when you're going to bottle?

If the reading isn't changing then fermentation has ceased . . . The same is true of the hydrometer . . . Can you rely on that??

With a lot (majority?) of brewers who brew with no temperature control a sudden temperature drop overnight can prematurely cause the yeast to cease fermentation, and they never really restart. Even a stable hydrometer reading in these circumstances is going to cause issues.

BB Have you seen the hydrometers that are used in breweries? They are 60-80 quid a pop and only cover ranges of 0.0200 . . . so you need a set of 5 or 6, you are also talking of a sample size of 700ml, which if you are doing it properly will take an age to cool to the 'reading temp' (temperature corrections are nothing more than a fudge factor IMO and the bigger the temp difference the bigger the Fudge) therefore using them during the 'Hot' side of the process is pointless, and also expensive considering how fragile they are. The refractometer comes into it's own in these circumstances.

A typical £2.50 SR home brew hydrometer bears only superficial resemblance to a Real Brewers Hydrometer, and given the way most home brewers use them about as useful as using a chimpanzee with a stick to measure gravity! (sorry guys ) I find the 'extended scale' home brew hydrometers to be useful, but even these the paper scale moves in the tube, so occasionally they need 're calibrating' with gentle tapping to move the scale back so that it reads 1.0000 in distilled water. They also have the issue of being 'short range' (1.000-1.050 and 1.050 to 1.100), and requiring larger samples.

Then again you may well actually say, I know a Kg of malt gives me 308 degrees, so 4 kilos in 23L will give me (guess) 1.040 and my bother taking gravity readings at all?

[fisherman]

I have used my refractor meter with good results But honestly don't use one much now since I started batch sparging.I find fly sparging unnecessary as the results from batch sparging are so good since watching the Denny Brew website and video has completely changed my approach to sparging.my last two brews using the refractometer were just as good as back sparging but so much more trouble having to check and recheck the liquid. I have found it pays to get things done fairly quickly including overmashing in time and over sparging generally it may cost me a little more in grain a year but I don't really mind this . I use the refract ohmmeter just to check the last runnings John normally around in 1015 which suits me fine happy brewing and enjoy