Refractometer question

[BanjosLaughter]

Evening all; I tried to find the answer to this on the ever omnipotent google, but I am not sure I know how to phrase the search. I am back to brewing after years off; when I left off I used a refracts meter that read only brix. I lost that one somewhere in a move and had to purchase a new one. This one has Brix and SG. My question is this. Do I need to calculate something even though it has SG? I’m frustrated because my last beer seemingly petered out at 1.044, but when I kegged it, it is definitely not a 4% beer like the measurements suggested. This time I used a tilt hydrometer, it reads at 1.024 but I just took a manual refractometer reading and it reads 1.047. I calibrated the refractometer before I used it this time, I am thinking I am missing some step in the conversion process. Not sure if this question makes sense….. Google doesn’t seem to think so. Thanks for any info you are willing to dispense.

 

[DBhomebrew]

Yes, absolutely. You can ignore the SG scale and proceed as you used to. Input original and current observed gravities in Brix, calculator spits out the actual gravity in SG.

Part II here...

https://www.brewersfriend.com/refractometer-calculator/

 

[AlexKay]

To follow up: when you’re measuring wort, you can use the SG scale and it will be accurate. Once fermentation has started and alcohol is present, you can’t figure out the gravity unless you have the original and current refractometer readings, in Brix.

 

[dmtaylor]

Responses above are correct. A refractometer does not read accurately when alcohol is present. Fortunately, the equations for conversion to SG numbers are pretty accurate within 0.001-0.002 gravity units as compared with a real hydrometer.

Your safest bet is to ignore the SG scale of a refractometer completely, and use a calculator like the one linked above to convert Brix to SG.

Also be aware, a Tilt might read accurately before pitching, but is not as accurate anymore once there is a lot of yeast and hop schmutz stuck to it. Results are highly variable if stuff is stuck to it.

 

[bobtheUKbrewer2]

dmtaylor - hydrometers do not read accurately once alcohol present, but the error is best ignored. I measure say 10.5 brix at start and maybe 5.3 brix at bottling, so around 4%.

3.9 or 4.1 , who cares........hic

 

[dmtaylor]

Hydrometers do read accurately with alcohol present.

You are correct about all the rest of it. Your ABV is about 4.0%, plus or minus 0.1%.

For low finishing gravities (high attenuation), Sean Terrill's calculator is slightly more accurate than Brewer's Friend.

 

[bobtheUKbrewer2]

dmtaylor - the gravity of your final beer is made up from a sugar solution and an alcohol solution. The hydrometer measures the density of the sugar solution, say it is just sugar solution. But add alcohol and the liquid becomes LESS Dense, and so the hydrometer sinks deeper into it. Only a little lol but it does............I only go on about this because so many people say a refractometer is inaccurate.....

 

[Skeeter686]

Oh, where's my damned tricorder???

 

[dmtaylor]

dmtaylor - the gravity of your final beer is made up from a sugar solution and an alcohol solution. The hydrometer measures the density of the sugar solution, say it is just sugar solution. But add alcohol and the liquid becomes LESS Dense, and so the hydrometer sinks deeper into it. Only a little lol but it does............I only go on about this because so many people say a refractometer is inaccurate.....

Perhaps the point you are trying to make has something to do with apparent attenuation (used by homebrewers) versus real attenuation (used by scientists). This can be observed by people figuring that the lowest SG reachable in a beer as being 1.000, which is actually NOT true because alcohol has a density far lower than that. This is easily confirmed by any wine, mead, or cidermaker who has seen SG as low as about 0.992 due to this effect -- in these conditions, the concept of apparent attenuation (used by homebrewers of beer) becomes useless. That being said, the lowest SG that I have seen discussed in beer is about 1.001-1.002, and the reason for this is not that 1.000 is some kind of limit but that wort inherently contains a fair proportion of complex unfermentable sugars and dextrins, whereas simpler honey & fruit based fermentations do not.

If that's NOT what you were alluding to at all... then, well, this has been a nice discussion anyway. I hope it helps someone out there.

 

[doug293cz]

dmtaylor - hydrometers do not read accurately once alcohol present, but the error is best ignored. I measure say 10.5 brix at start and maybe 5.3 brix at bottling, so around 4%.

3.9 or 4.1 , who cares........hic

Hydrometers respond to density, and usually have scales calibrated for specific gravity (the ratio of a solution's density to the density of water.) An SG measurement with a hydrometer is accurate (assuming the instrument is functioning properly) no matter what the composition of the solution is. If the solution consists of only water and sugar (and sugar like compounds), then the SG can be correlated to the sugar concentration.

Some hydrometers have scales that are calibrated in °Plato or °Brix, both of which correlate the weight % of sucrose in a water solution vs. the density of the solution. The measurements are only accurate for binary solutions of sucrose and water. The error for solutions of other types of sugar are small. Like a refractometer. a Plato or Brix reading hydrometer will give erroneous readings if alcohol (or other non-sugar constituent) is present. However, the errors will be different than for a refractometer with non-binary solutions.

Refractometers respond to index of refraction. The scales in the refractometers we use usually represent a correlation between index of refraction and °Brix and/or SG. The readings are only accurate for solutions of sucrose in water. If the measured solution contains anything other than water and sucrose (or things that affect the IR similar to sucrose) then the reading will be in error. People have figured out correlations that allow for reading correction if you know the original °Brix, and the sample contains only water, sugar (or sugar like compounds), and ethanol.

Ethanol has a lower density than water or sugar, so a °Plato or °Brix scale hydrometer will read too low in the presence of ethanol. Ethanol has a higher IR than water, so a refractometer will read too high in the presence of alcohol.

Brew on

 

[doug293cz]

That being said, the lowest SG that I have seen discussed in beer is about 1.001-1.002, and the reason for this is not that 1.000 is some kind of limit but that wort inherently contains a fair proportion of complex unfermentable sugars and dextrins,

I brewed a brut IPA that finished at an SG of 0.996, measured with a hydrometer. I got rid of all the dextrins, and other unfermentable sugar, by adding amyloglucosidase enzyme to the fermenter.

Brew on

 

[dmtaylor]

I brewed a brut IPA that finished at an SG of 0.996, measured with a hydrometer. I got rid of all the dextrins, and other unfermentable sugar, by adding amyloglucosidase enzyme to the fermenter.

Brew on

I actually intended to mention enzymes in my previous post, this is a way to get a beer less than 1.000. But I forgot to mention it. Cheers.

 

[bobtheUKbrewer2]

Doug, brilliant post. Shall we start on the fallacy of hot side aeration next ?

 

[balrog]

To follow up: when you’re measuring wort, you can use the SG scale and it will be accurate.

One man's experience here, but my SG scale in the refractometer was incorrect by about 4 points.

 

[Nagorg]

My older refractometer only displays brix. I've seen the ones that have both brix and SG but on the ones I've seen, the brix scale is much too small for my eye to read.
I wouldn't use the SG scale personally as I'm used to brix, plus I have a hydrometer. And my personal experience using the post ferment calculators with brix is that they are reasonably close to what my hydrometer reads when checked.

I'll add that different calculators will give slightly different results. So I'll usually use 3-4 of them and average the results for what I "run with". This is close enough for this homebrewer!

Anyone know where to find a good brix refractometer with an easier to read scale and no SG? Wouldn't mind having a backup in case something happened to the one I have now.

 

[doug293cz]

Doug, brilliant post. Shall we start on the fallacy of hot side aeration next ?

This is not the place for that discussion. Head over to the Low Oxygen Brewing sub-forum if you want to poke that hornets' nest.

And, thanks for the compliment.

doug293cz
HBT Moderator

 

[doug293cz]

One man's experience here, but my SG scale in the refractometer was incorrect by about 4 points.

Unfortunately this is true of too many dual scale refractometers. One way to tell: if 20 Brix doesn't equal 1.083 SG on the scales, then your refract is not good.

One possible reason for "bad" SG scales in refracts might be a built in wort correction factor (which may or may not be appropriate for the worts actually being measured.) A wort correction factor compensates for the fact that beer wort is not a simple sucrose/water solution, and the index of refraction does not behave the same way with changing SG.

Brew on

 

[bobtheUKbrewer2]

Doug - a mod with a lot of detailed knowledge and a great sense of humour.....I bet he makes sourdough bread and grows tomatoes...

 

[day_trippr]

I remember a favorite vendor on HBT switched his refractometer source as the SG scale was quite a bit off nearing the denser end of the scale. The supposition was the Brix v SG scales were set up for wine instead of beer...

Cheers!

 

[doug293cz]

Doug - a mod with a lot of detailed knowledge and a great sense of humour.....I bet he makes sourdough bread and grows tomatoes...

Don't bake or grow, but my wife and daughter try to grow tomatoes.

Brew on

 

[VikeMan]

To follow up: when you’re measuring wort, you can use the SG scale and it will be accurate.

I would say accurate-ish. But even before there's alcohol present, there's still the fact that beer wort is not a pure sucrose solution, so a wort correction factor is needed. Now, any particular dual-scale refractometer may have a wort correction factor already embedded in its "SG" scale, but unfortunately, different worts need different correction factors for the correction to be perfect. That said, in many cases, it may be "close enough" (depending on how close the brewer wants it in order to declare it close enough).

 

[jerrylotto]

Also be aware, a Tilt might read accurately before pitching, but is not as accurate anymore once there is a lot of yeast and hop schmutz stuck to it. Results are highly variable if stuff is stuck to it.

I don't rely on accuracy with my tilts, I use them to detect change. Whatever the number is, when it stops changing I know fermentation is done.

 

[Graham H]

I don't rely on accuracy with my tilts, I use them to detect change. Whatever the number is, when it stops changing I know fermentation is done.

That’s how I use my refractometer. I can do a single hydrometer sample for FG, and only need a few drops on each refr check to figure out when the batch is ready for the FG test.

 

[CascadesBrewer]

I remember a favorite vendor on HBT switched his refractometer source as the SG scale was quite a bit off nearing the denser end of the scale. The supposition was the Brix v SG scales were set up for wine instead of beer...

That is what I found with my last refractometer. The "SG Wort" scale was okay in the 1.050-ish range (which works well for pre-boil for 90% of my beers) but drifted off at higher gravities. I recently made the mistake of leaving that in a pan that I filled up with water and I could no longer read the scales. I replaced that with another $15 model that seems better made.

Kegland recently put out a refractometer designed for brewers. It has a built in light (not sure how useful that is) but it might have a better SG scale. David Heath put out a video on YouTube comparing the Kegland to cheap vs digital (but I think he ignored common advice to get an accurate reading from a cheap refractometer). The Kegland does claim to be water proof.

 

[balrog]

Reminds me that it’s time for the pseudo-semi-sometimes-bi-annual-ish mixing of 1.010, 1.040 sugar water solutions and hydrometer/refractometer double check hoedown soirée.

 

[bobtheUKbrewer2]

a scientific laboratory could do refractometer Fg readings and then determine "sugars" and alcohol content - but they don't - discuss.........

 

[balrog]

a scientific laboratory could do refractometer Fg readings and then determine "sugars" and alcohol content - but they don't - discuss.........

I’m sure for $$$ you can find a lab to do it. But homebrewers by and large are not the type to do $$$ analysis stuff. $$$ equipment stuff, yes.

 

[day_trippr]

Right - I'd bin that in the same "It would be neat to know but too expensive to find out department" as measuring actual IBUs...

Cheers!

 

[doug293cz]

a scientific laboratory could do refractometer Fg readings and then determine "sugars" and alcohol content - but they don't - discuss.........

No. Can't be done with a single index of refraction reading, no matter how good your equipment. In a mixture of water, sugar, and alcohol, you have two components that can raise the index of refraction from that of pure water. Basically, it's a two variables but only one equation problem - there is not a single unique solution.

Brew on

 

[balrog]

Perhaps if they carried it between them tied with a bit of creeper?

 

[Dland]

If anyone reading this thread and are feeling like they are missing something and need to get a refractometer and do particle/solution exclusion calculations, don't worry.

A cheap glass hydrometer, either brix or SG will let you know how your brew is doing and what is has done. Might take a few batches to get used to, but no batteries or software updates.

While using simple hygrometer will not get you lab accurate numbers you can use in a scientific paper or PHD thesis, it will tell most of us what we need to know regarding the fermentation progress and relative ABV of our brews.

Very accurate data does have it's place, especially in commercial applications, and many on this site like to voluntarily go down technical rabbit holes, and that is cool too.

 

[DBhomebrew]

If anyone reading this thread and are feeling like they are missing something and need to get a refractometer and do particle/solution exclusion calculations, don't worry.

A cheap glass hydrometer [or very nearly just as cheap plastic refractometer] will let you know how your brew is doing and what is has done. Might take a few batches to get used to, but no batteries or software updates.

While using simple hygrometer [or refractometer] will not get you lab accurate numbers you can use in a scientific paper or PHD thesis, it will tell most of us what we need to know regarding the fermentation progress and relative ABV of our brews.

Very accurate data does have it's place, especially in commercial applications, and many on this site like to voluntarily go down technical rabbit holes, and that is cool too.

FTFY

 

[AlexKay]

A refractometer will tell you when your fermentation is done. It will also let you monitor consistency batch-to-batch. Nobody I know has broken a refractometer. (My dogs chewed on mine a little, but it still works fine.) And you need only a few drops to make the measurement.

A refractometer will not tell you the ABV without using a calculator with both initial and final measurements. Neither will a hydrometer. And homebrewers don't need +/-0.3% accuracy anyhow.

If you know your volume, a hydrometer will tell you what your beer weighs. A refractometer will not.

You can get the apparent attenuation from initial and final measurements using a hydrometer, but will need a calculator to do this with a refractometer. Neither will let you determine actual attenuation without calculators and assumptions/guesses.

 

[dmtaylor]

To put it all a couple more ways:

Tools are about as useful or useless as the user.

There is a right way to use any tool. Meanwhile, using a tool the "wrong" way might still be OK, as long as the user understands the limitations and adapts application appropriately to ensure effective results.

In any case, if accurate results are desired, calibration is essential. Without calibration against known standards, you are shooting in the dark. Conversely, if accuracy or precision are not important, then why measure at all.

 

[shavy]

Reminds me that it’s time for the pseudo-semi-sometimes-bi-annual-ish mixing of 1.010, 1.040 sugar water solutions and hydrometer/refractometer double check hoedown soirée.

Right!

 

[balrog]

Nobody I know has broken a refractometer.

Well.
Does dropping it in the boiling brew kettle, such that it no longer functions count?

Yeah. I can teach you that golf shot.
It’s in my bag.