Refractometer

[DocAnna]

Being an auld duffer or more accurately an old buffer I take a picture with my phone and enlarge it.
View attachment 45408

I do rather suspect I've been reading my hydrometer about 0.002 too low based on this, well at least if I'm consistent the ABV will still be correct!

 

[peebee]

Everyone I have seen has been calibrated to 20C.

Yes you are probably right! It'll be printed in the hydrometer, I have to check everytime!

It's 20C. The older spec was 16C (60F) and Americans still use this (and many labs elsewhere which is odd). They also have ones to work in tropical places calibrated at thirty something.

<EDIT: 60°F is more accurately 15.5556°C, not 16, but as no-one wanted to correct me (quite right too) I'll do it myself! The "labs" still use 60°F but should really be using 20°C, with the "reference" being (water @) 4°C; now that's just getting silly. Such hydrometers read the actual density of the liquid, not the relative density, or SG. Okay, I'm not just getting silly, I'm getting incoherent now!>

 

[Funny pun]

I never thought to use a refractometer for brewing, I have two, both with SG scales.
Much easier and less hassle than a hydrometer.
most modern ones have automatic temperature compensation too, within a limited range of temperatures, and although they get less accurate towards the extremes of their range in my opinion the results would be more than accurate enough for brewing purposes.

 

[peebee]

I never thought to use a refractometer for brewing, I have two, both with SG scales.
Much easier and less hassle than a hydrometer. ...

Beware of those SG scales on refractometers. They are only of use before fermentation. Once alcohol is in the mix, the SG scale is useless (use the BRIX scale with an online calculator, which also needs the OG to estimate the amount of alcohol).

 

[Funny pun]

Beware of those SG scales on refractometers. They are only of use before fermentation. Once alcohol is in the mix, the SG scale is useless (use the BRIX scale with an online calculator, which also needs the OG to estimate the amount of alcohol).

Ah, thanks for pointing that out.
It’s obvious if you think about it, but I obviously didn’t think about it.

 

[StJayJay]

Resurrecting this thread for a quick refractometer question:
Does dissolved CO2/carbonation affect the readings?
Just curious, thought fermentation had stopped after a few stable readings. It’s been transferred to a keg for force carbing (no priming sugar), took a wee sample to check carbonation today and put a drop on the refractometer out of interest, and the reading had dropped a little.

 

[RichardM]

Resurrecting this thread for a quick refractometer question:
Does dissolved CO2/carbonation affect the readings?
Just curious, thought fermentation had stopped after a few stable readings. It’s been transferred to a keg for force carbing (no priming sugar), took a wee sample to check carbonation today and put a drop on the refractometer out of interest, and the reading had dropped a little.

Alcohol affects the reading after fermentation. You need to make a calculation to correct the reading or, easier, use a hydrometer.

 

[StJayJay]

Alcohol affects the reading after fermentation. You need to make a calculation to correct the reading or, easier, use a hydrometer.

Yeah, realise that, I’ve been using the refractometer calculation tool on brewers friend since I got one last year so comfortable in how to use it. Used it alongside a hydrometer for the first couple of times for belt and braces.

My question is after a number of stable readings around expected FG over a few days, I assumed fermentation had stopped. Since kegging and carbing, the reading is lower. I wondered if CO2 may skew readings.
Other possibilities are that in racking, I’ve roused some yeast, and where I carb is a touch warmer than where I was fermenting, so that may have promoted a little more yeast activity, so maybe the yeast wasn’t quite done, hence a further drop in reading.

 

[RichardM]

Yeah, realise that, I’ve been using the refractometer calculation tool on brewers friend since I got one last year so comfortable in how to use it. Used it alongside a hydrometer for the first couple of times for belt and braces.

My question is after a number of stable readings around expected FG over a few days, I assumed fermentation had stopped. Since kegging and carbing, the reading is lower. I wondered if CO2 may skew readings.
Other possibilities are that in racking, I’ve roused some yeast, and where I carb is a touch warmer than where I was fermenting, so that may have promoted a little more yeast activity, so maybe the yeast wasn’t quite done, hence a further drop in reading.

I've never measured SG after carbing but I can see that it would make a difference

 

[bobukbrewer]

RichardM = hydrometers are also inaccurate due to alcohol in solution...

 

[Agentgonzo]

I find successive readings from my refractometer can vary wildly (half a brix).

They are also calibrated for fructose/sucrose, which means you need to apply a "wort correction factor". Mine (0.9) seems to be deferment from values on the internet . I just use it to get a ballpark figure and see when fermentation is done. Then I take og/fg readings with a hydrometer

 

[bobukbrewer]

I have never seen a correction factor that high - ( low) - 1.04 seems typical, also to vary from say 7 BRIX to 7.5 BRIX is worrying - unless your instrument is 0 - 50 BRIX - maybe ask someone else to take some test readings ?

 

[sifty]

I use mine heaps during the brew process to see how things are going. Always within a point of the hydro. Take 'official' hydrometer readings for OG and FG but also use an iSpindel so have a reasonable idea of where things sit amongst all the info...

Wish there was something as simple (and miserly) as the refractometer for accurate readings during fermentation...

 

[peebee]

I'd agree with @bobukbrewer, the BRIX correction factor is typically 1.04; this is to correct a reading calibrated for sucrose when measuring a solution that is predominantly maltose. Which has always bothered me; that at the end of fermentation we account for the alcohol, but not for the solution now being predominantly of unfermentable dextrin. Doesn't make enough difference? It's the headache of making a tool designed for an entirely different purpose do this job.

I don't agree with @bobukbrewer that a hydrometer is inaccurate due to alcohol! The hydrometer just continues to read the specific gravity (relative density) whatever fluid it sits in - but our interpretation of the reading might be distorted by alcohol (especially if drinking the stuff too!). But we've been doing that for years, so I guess we've just grown up with whatever error it creates.

But stuff fiddly hydrometers, I use pyknometers (if it's going to be fiddly, I go for really fiddly).

 

[Agentgonzo]

I have never seen a correction factor that high - ( low) - 1.04 seems typical, also to vary from say 7 BRIX to 7.5 BRIX is worrying - unless your instrument is 0 - 50 BRIX - maybe ask someone else to take some test readings ?

Yeah, I found it odd too. The scale is 0-30 brix. But as I said, I have my own calibration for it and only use it to get a ballpark reading to see if fermentation is done (I take multiple readings and average them out) so I don't rely on it nor need super-accuracy from it. IT was from Amazon, so it's not like I was expecting a perfect scientific instrument.

 

[bobukbrewer]

peebee - make up a 100 ml sugar solution such that refractometer reading is 5 BRIX. Now add 4 ml of vodka. The reading will now be less than 5 BRIX because vodka weighs less than water. BUTTTTTTTTTTT, I think the error is around .002 on the hydrometer and can be ignored. If I want a 3.8% beer and it turns out 3.7 or 3.9 then I am happy.

 

[BrewsWayne]

This is not inexpensive, but it is accurate
Anton-Parr EasyDens

$349.00US

 

[peebee]

peebee - make up a 100 ml sugar solution such that refractometer reading is 5 BRIX. Now add 4 ml of vodka. The reading will now be less than 5 BRIX because vodka weighs less than water. BUTTTTTTTTTTT, I think the error is around .002 on the hydrometer and can be ignored. If I want a 3.8% beer and it turns out 3.7 or 3.9 then I am happy.

Thank you! That is a good observation, but perhaps not in the way you (or many others?) expect?

I said, "It's the headache of making a tool designed for an entirely different purpose do this job.".

The job it was intended to do was measure optical refractive indexes of liquids. The job we are expecting it to do is measure the relative "weight" (density) of the liquid, relative to water at n°C that is. ☺

 

[bobukbrewer]

peebee - ok I am out of discussion - both hydrometers and refractometers cannot cope with alcohol is a sugar solution - but the errors are very small - better to concentrate on other aspects of brewing perhaps - it is dry hopping for me...

 

[lancon]

I think what I was trying to get to. Is there a place to buy an accurate hydrometer. These were cheap from the same local home brew shop. I was wondering if there was one available that was guaranteed to be calibrated properly?

https://www.stevenson-reeves.co.uk/reeves/HPKM.htmI use a 1.005-15 for FG and 1.030-60 for OG. The FG one is certified, (and expensive)