Refractometers and temperature compensation

The Homebrew Forum

Help Support The Homebrew Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
Let your brew ferment for at least 10 days then measure SG. Leave another 2 days and repeat. 9 times out of 10, fermentation is well finished and the 2 readings are the same and you're good to go minus 200mls if beer asad1
Yes but will that work with a refractometer? I am assuming yes because as long as its a consistent reading it should be right
 
Hi Galena
But when you say it is a faff, it seems to me (I stand to be corrected) all I need to do is put the OG and the current reading in Brix into a calculator like Brewers Friend or Brewfather and it does the correction for you and gives you the gravity? What could be simpler? What am I missing?
... have a read of the notes underneath the Brewers Friend refractometer calculator there (link), I think all that stuff around Brix WRI vs Brix/Plato and calibrating a Wort Correction Factor will be the "faff" being talked about (and what they don't mention in that text about calibrating refractometers is how it's quite common to find you need a different correction factor for dark coloured worts than when measuring lighter worts :confused.: ) ... and then there's the difficulty of getting a clear reading when there's any sort of turbidity in the wort you're measuring.

Don't get me wrong, I'm very happy with my refractometer ... but I only use it to check stability of (unconverted Brix) gravity measurements to make sure fermentation is finished ... I use my hydrometer for OG and FG measurements, the 100ml samples for OG get put back in the FV and fermented with the rest, the 100ml for FG (after stability is verified by refractometer readings) gets sampled as a first taster athumb..

Cheers, PhilB
 
I use my refractometer during the mash to get a rough idea. Then put my hydrometer in my fermenter for a reading just before I add my yeast. Then leave it in. Fourteen days later. Check for my FG reading....
 
With the refractometer?
No. I use the hydrometer that I had left in the brew......
I have had my refractometer 4 points out on my postboil gravity 1060 hydrometer and 1056 refractometer.
But my last brew they read the same. So, I am very happy with it as a quick and easy rough guide....
 
No. I use the hydrometer that I had left in the brew......
I have had my refractometer 4 points out on my postboil gravity 1060 hydrometer and 1056 refractometer.
But my last brew they read the same. So, I am very happy with it as a quick and easy rough guide....
Indeed, my point though is not whether it is inaccurate so far as an actual FG reading is concerned, that can be done with a hydrometer at leisure, my question is whether it can be used to check for end of fermentation, so for instance if I check the Brix for 3 days in a row and the reading remains the same can I reliably say that fermentation has ended? If it has I can do an FG with the hydrometer and then bottle at leisure.
 
Hi Galena
if I check the Brix for 3 days in a row and the reading remains the same can I reliably say that fermentation has ended?
... Yes ... if fermentation was continuing, then there would be less sugar in the sample and the refractometer reading would be lower ... not as low as it would have been if you'd somehow removed sugar without it turning into more alcohol, but still lower ... stable readings over that period means fermentation is finished athumb..

Cheers, PhilB
 
Hi Galena
... Yes ... if fermentation was continuing, then there would be less sugar in the sample and the refractometer reading would be lower ... not as low as it would have been if you'd somehow removed sugar without it turning into more alcohol, but still lower ... stable readings over that period means fermentation is finished athumb..

Cheers, PhilB
Thanks Phil that is exactly what I wanted to hear :)
 
Try reading this if you want to get really geeky about measuring specific gravity Hydrometer? Refractometer? Or something better? - Home Brew Forum
This confused the hell out of me …

The link is to one of my threads (thanks @RichardM), but it links to the "other" UK site (Jim's). That didn't click immediately! I'd just add, be cautious of that thread: When I first started it (back in May 2020) I was learning as I went along. The thread doesn't develop into "accurate" information until later.

And it probably is "geeky". I guess I'm a geek?
 
I use mine as others have said to test the gravity during the mash, pre boil and before pitching the yeast. Speeds everyone up as the two or three drops into the glass of the refractometer are cool after a few seconds whereas a hydrometer sample would take ages to cool.

For a sanity check I pour a sample from wort left in the pump/pipes into a trial jar and use my hydrometer after pitching. It’s usualy within 1 point or so 👍
 
RichardM - a hydrometer is also inaccurate due to the presence of alcohol in the FG measurement - the refractometer is off one way and the hydrometer is off in the other way - I reckon the error is around .0015 so not that critical - consistency is more important for me....
 
I’m yet to get reliable reading from my refractometer, but I find it is a useful guide. Mine was bought from MM (I think) and was around £35 ish and is supposed to be ATC, but I still have to calibrate it every time with RO water first and this reading does vary, I assume because of room temperature variations.
The refractometers we usually use are designed for wine making (fructose) which is pretty consistant, if we’re using them for beer, the cocktail of different sugars in our wort will vary by recipe and needs that correction factor to work. It does sound like a faff, but if you’re using software like BeerSmith it’s incredibly easy.
I take a hydrometer reading for OG and from this sample also note the refractometer reading, these both get entered for that session and this gives me my refractometer calibration, which it stores for that brew. All subsequent readings simply have the option selected that calculates for alcohol present and it uses the OG already entered as reference.
I take two readings a day until gravity settles down, the sample drawn can be as small as practical, about a tablespoon. I’ve found the clearest reading uses only one single, small drop on the glass, it doesn’t matter how turbid the sample is.
I still use a hydrometer to take the FG from a de-gassed sample taken from the final serving keg so the beer has been fully mixed. I don’t get a reliable FG calculation from the refractometer, but it is a useful indication.

<edit> I take regular samples from a sampling port, I’m not endorsing lifting the lid on a FV several times a day! 🤭
 
I’m yet to get reliable reading from my refractometer, but I find it is a useful guide. Mine was bought from MM (I think) and was around £35 ish and is supposed to be ATC, but I still have to calibrate it every time with RO water first and this reading does vary, I assume because of room temperature variations.
The refractometers we usually use are designed for wine making (fructose) which is pretty consistant, if we’re using them for beer, the cocktail of different sugars in our wort will vary by recipe and needs that correction factor to work. It does sound like a faff, but if you’re using software like BeerSmith it’s incredibly easy.
I take a hydrometer reading for OG and from this sample also note the refractometer reading, these both get entered for that session and this gives me my refractometer calibration, which it stores for that brew. All subsequent readings simply have the option selected that calculates for alcohol present and it uses the OG already entered as reference.
I take two readings a day until gravity settles down, the sample drawn can be as small as practical, about a tablespoon. I’ve found the clearest reading uses only one single, small drop on the glass, it doesn’t matter how turbid the sample is.
I still use a hydrometer to take the FG from a de-gassed sample taken from the final serving keg so the beer has been fully mixed. I don’t get a reliable FG calculation from the refractometer, but it is a useful indication.

<edit> I take regular samples from a sampling port, I’m not endorsing lifting the lid on a FV several times a day! 🤭
One drop, well that is different I will have to try that. Interesting information thanks and this is kind of how I envisage using mine (when it arrives). I have a tap for drawing off a little so no need to keep opening up the FV. Cheers
 
Yeah, I had read three drops, and that works for for the water calibration, but I used to find three and even two drops of wort gave a really blurred, vague line. Flicking the cover up and down a few times cleared the line up but I think a single drop has the same effect of creating a very thin film of liquid. Hope it works for you!
 
Yeah, I had read three drops, and that works for for the water calibration, but I used to find three and even two drops of wort gave a really blurred, vague line. Flicking the cover up and down a few times cleared the line up but I think a single drop has the same effect of creating a very thin film of liquid. Hope it works for you!
Cheers, will certainly give it a try
 
RichardM - a hydrometer is also inaccurate due to the presence of alcohol in the FG measurement - the refractometer is off one way and the hydrometer is off in the other way - I reckon the error is around .0015 so not that critical - consistency is more important for me....
Alcohol is compensated for by using a calculator (essential if the wort has started fermenting) but the wort compensation factor used by those calculators has to compensate for the difference between a predominantly maltose solution (wort) and the sugar solution native to BRIX (@Edison, I thought that was the disaccharide sucrose not the monosaccharide fructose?). A factor of 1.04 is often used as the default. But as wort ferments that correction factor must change but I've no idea how much the change is relevant?

Yeah, I had read three drops, and that works for for the water calibration, but I used to find three and even two drops of wort gave a really blurred, vague line. Flicking the cover up and down a few times cleared the line up but I think a single drop has the same effect of creating a very thin film of liquid. Hope it works for you!
I'll have to try that too! I've always "guessed" which obviously isn't the best.
 
Sorry, not really sure of the sugars in fruit juice/wine must, just assumptions and half-remembered comments im afraid!

My latest brew started at hy 1.058, re 14.0 (corr 0.98). Finished at hy 1.017, re 7.6 (12.9% crystal malt) so the refractometer calculates at 2 gravity points lower than measured with the hydrometer, but not a million miles out (0.3% abv difference).
 
RichardM - a hydrometer is also inaccurate due to the presence of alcohol in the FG measurement - the refractometer is off one way and the hydrometer is off in the other way - I reckon the error is around .0015 so not that critical - consistency is more important for me....
I never new that. I wonder how close it would be to take a reading with a hydrometer and a reading with a refractometer and then split the difference without doing any corrections.
I suppose that would need them to both be out by near enough the same amount.
 
I never new that. I wonder how close it would be to take a reading with a hydrometer and a reading with a refractometer and then split the difference without doing any corrections.
I suppose that would need them to both be out by near enough the same amount.
Brewing is so entrenched in it's use of "apparent" SG that going with anything else will cause confusion. As does "apparent" and "real" attenuation. You just need to stick with the accepted measures unless some radical change takes place (unlikely).
 

Latest posts

Back
Top