Refractometer and Variability of Readings

Not sure if the bubbles would explain that much of a discrepancy, though it's something to consider. I always make sure I have a clean sample - no bubbles or residue. I usually take two readings, but they almost always agree with each other. When they don't, I take extra care to get clean samples until they do. And, in the rare case when the gravity seems 'wrong', it's virtually always confirmed by the hydrometer.

 

are you using the refract pre and post fermentation?

I use it only during the mash, boil and post boil, and confirm its in line with my hydro for the pre and post boil og. I never use it once fermentation has started. alcohol will toss it out of kilter, and while there are calculators out there to figure it out, i find it not as accurate enough for my peace of mind.

How much are you putting the glass though? I put enough that it pours off the front of the refract and then close the top of it. bubbles never seem to affect my readings.

 

How long are you waiting for the sample to cool on there? despite the atc, i find it need to wait around 2 minutes for what little bit to level out and cool. Also, i put more on there than a couple drops. put enough that it runs off the glass plate and see if it helps. could be it needs calibrated too. I had to calibrate mine.

 

I cool my samples down to 65° (the temp I calibrated at) before putting about 3 drops on the plate. I just pick the plastic lid up a few times to get the bubbles out. So far, my readings have been damn near spot on when tested against a hydrometer.

There is also the possibility that your refractometer is defective...

 

Mine is brix only, as well. I was a bit irritated at first, but the online conversion calculator is simple enough to use. Most of my beers end up in similar brix ranges, so I pretty much have the conversion memorized anyway.

 

I've never seen a "this refractometer works like a champ!" thread, or any discussions of the use of refractometers that didn't have tons of 'qualifications.'

 

People tend not to post comments when things work as advertised (as a refractometer tends to do). In the case of a refractometer, it would only serve as troll bait as the predictable responses flood in saying that it's useless in the brew house, followed by tons of 'qualifications' as users feel compelled to defend their choice of tools.

BTW, when was the last time you saw a "this hydrometer works like a champ!" thread?

 

I don't know if there are any cons to my technique, but I get accurate readings much quicker than that. When I brew I usually have a 5 gallon bucket with plain water in it by the brew rig that I put my mash paddle and spoon in. When I take a refractometer reading, I simply draw some wort into my pipette, flip the pipette upside down in my hand (so I'm now holding the drawing tip with my fingers and the sample slides down into the end you squeeze to draw the sample) and I place the squeeze end into the water bucket for about 10 seconds to cool the wort down quickly. I then flip the pipette around again and push the sample onto the refractometer plate to take a reading. I do this despite having an ATC refractomer and despite the instructions saying that a hot sample put onto the refractometer plate will cool quickly. It just comforts me to know the sample I put on the plate is already closer to the calibration temp range.

 

Never, because they always work like a champ*. Point taken.

Now what does that say about refractometers...

*use only as directed. Side effects may include fever, chills, severe flatulence, preference for country music, an inability to admit that reality TV really sucks badly, gastric disorders, halitosis, elephantitis of the nuts, dyslexia, podo-bromadrosis (aka stinkfoot), uncontrollable canine leg-humping disorder, madonna/dennis rodman fetishes, itchy butt syndrome, geriatric profanity disorder, republicanism, venereal disease, brain tumors, and sudden failure to continue living syndrome.

 

The versions with the extra 'SG' scale are no more useful than the ones without. That's because they are calibrated to one specific sugar type, not to the mixture of sugars in beer wort. That's why you still need a calculator to convert to SG, even for OG readings.

 

You can do a two point ( or more if you wish) calibration by doing the following.

Zero Brix by using distilled or RO water.

Make a solution of sugar and water to x Brix. I used 10 grams of sugar, dissolved in 75 ml of water, then topped up with water to 100 ml of solution. The hydrometer was 1.040=10 Brix, the refractometer was 9 Brix! It has been in used and abused for many years.

 

The exact sugar composition make a difference when using a refractometer because each sugar affects the index of refraction of the solution differently. (This is because each sugar has a different electronic structure, which is directly affects its optical properties.) Thus the mapping of refractive index to density is slightly different for each sugar.

Indeed, a hydrometer directly measures density.

 

multiply the brix by 4 to get sg.

my refractometer always works. every time ive double checked with hydrometer it was always spot on, even during fermentation using online calculators w/ adjustment spreadsheet built in.

do you do partial boils? cuz i do and the first couple times i used my refractometer i noticed the problems you are having too. once i diluted and mixed there is still a bit of disparity between the top and bottom. get a really long pipet and draw from as low as possible. once i did that, my experiences are like i said above.

oh and keep doing that pick up/release/repeat thing. that helps.

 

This is a rough rule of thumb, but note that it's not even accurate for pure sucrose solutions, let alone wort.

 

Still it's close enough for non competetive homebrewing. If I brewed for competitions I would possibly want it more precise but honestly, what are you going to do if your wort comes out in at 1.056 instead of the 1.054 you expected?