How accurate is your hydrometer?!!

[Clint]

What and where is an " expensive" hydrometer?
I just had to check before editing...what does it matter...the abv is still accurate even if the hydrometer is reading higher or lower as the difference(fg) will give the same result...

 

[Rogermort]

I use two hydrometers, one of which reads high and one low, and split the difference.

But I always find reading the thing pretty tricky because of the curve in the surface caused by surface tension, and the fact that there are often bubbles in the wort and/or a head in the jar.

Take a pic with your smart phone, then you can zoom in.

 

[Druncan]

It's a bloody expensive nightmare with fragile expensive kit,,,,, For commercial brews I have two S&R basic hydrometers and a refractometer for hot wort, that I use and clean and pamper. I OG with my calibrated S&R Saccharometer. I then have a FG S&R Sacc all I use with temp compensation charts from S&R. I have a calibrated thermometer I calibrate my digital temp probes with at near boiling and iced water. I de-gass (shaky shaky wait, repeat) all FG brews as the bubbles fek up the readings. I have to send two samples for (Brewlab) analysis for HMRC. Usually all spot on so far thankfully. The calculation for back adjustment of HMRC duty is complicated and I don't do complicated,,, life is difficult enough :tinhat:

 

[Edison]

What and where is an " expensive" hydrometer?

I was thinking of something like this:

https://www.themaltmiller.co.uk/product/large-hydrometer-1000-1060/
Or perhaps I could look at getting a Tilt, no need to keep taking refractometer readings daily as it logs results continuously and can be read remotely. I hear they're pretty accurate.

https://www.themaltmiller.co.uk/product/tilt-hydrometer-and-thermometer-yellow/
Really need to stop making excuses to spend money!

 

[Rogermort]

I'm happy with the 'amateur' kit I've got at home but in the micro that I used to brew in we used these which are good value. SG INSTRUMENTS – PBC BREWERY INSTALLATIONS

 

[dalecek]

I was thinking of something like this:

https://www.themaltmiller.co.uk/product/large-hydrometer-1000-1060/
Or perhaps I could look at getting a Tilt, no need to keep taking refractometer readings daily as it logs results continuously and can be read remotely. I hear they're pretty accurate.

https://www.themaltmiller.co.uk/product/tilt-hydrometer-and-thermometer-yellow/
Really need to stop making excuses to spend money!

Tilt looks like a nice piece of kit. Not quite sure I could justify the cost tho

 

[Clint]

...get to Wilko and spend £3..

 

[Edison]

I’m still using my Stevenson from 25 years ago. 2 points out isn’t that bad considering!

 

[Deathstar]

Remember for those who are using a refractometer, they are only of any use pre fermentation and that you also need to calculate your own wort correction factor. They are only really if any use for indication once fermentation has begun to confirm that fermentation is actually happening.

 

[lancon]

Remember for those who are using a refractometer, they are only of any use pre fermentation and that you also need to calculate your own wort correction factor. They are only really if any use for indication once fermentation has begun to confirm that fermentation is actually happening.

Really??

 

[peebee]

Remember for those who are using a refractometer, they are only of any use pre fermentation and that you also need to calculate your own wort correction factor. They are only really if any use for indication once fermentation has begun to confirm that fermentation is actually happening.

Na. The calculations and adjustments are valid all the way through fermentation. It's a myth that refractometers aren't valid after fermentation starts. But it is a pain having to use them with a calculator.

Whereas a hydrometer … you only need to read the result directly from the instrument. Assuming the scale is fixed correctly, that the scale is fixed and not likely to slip out of place, that the scale is printed correctly, that the frigile glass instrument wasn't broken last time it was used, that … (flippin' Mumbo Jumbo).

 

[GerritT]

Only thing worrying would be the FG giving inaccurate readings, so I'd bottle too early and risk overpriming.

 

[Edison]

I use the hydrometer to read OG as I rack to the FV and take a reading with the refractometer at the same time. Both readings get put into BeerSmith which calibrates my refractometer to that wort. All subsequent refractometer readings get automatically calculated by BeerSmith, but when it has hit FG the final hydrometer reading is never what was expected. I was considering that it being out of calibration was maybe the cause.

 

[peebee]

I use a pycnometer bottle now 'cos lots of fine parallel lines makes my eyesight go screwy. But there is no "is it or isn't it"; the full bottle weighs x grams and therefore (tap, tap, tap … the disadvantage is some work with a calculator is essential*) the SG is (precisely) y.

* The other "disadvantage" is having to learn exactly what "SG" is telling you - most people haven't a clue, but they still keep using it! If you fancy messing your head up (mine's permanently messed up anyway) try getting your head around this: Relative Density

 

[peebee]

I've just had a "brewday", and the pycnometer was in action. I'll give a brief summary so anyone interested can give it a go. (And I can look up this post up next time to remind me what to do!). If it looks too complicated for you, ignore it; don't tell me it's too complicated 'cos I'm not interested.


Brew into fermenter. A small sample (30ml) removed at near enough 20C. Pycnometer bottle filled (there's nothing to line up, no concerns about meniscus, no microscopic "scales" to read) and weighed. I know the weight of the empty bottle and it's precise volume. So I now know the weight of the sample (grams) which divided by the volume (millilitres) gives me the wort's density.

45.89gms - 18.28gms (empty bottle weight) = 27.61gms (weight of sample)
27.61gms / 26.37mls (volume of bottle) = 1.047g/ml (density of sample)

The density looks like an SG, but not quite there yet. The density of pure water at 20C is 0.998g/ml (look it up on t'Internet). Divide density of wort (at 20C) by density of water (at 20C). The water density is the "reference", in scientific circles the water would be at 4C (close to 1.000g/ml).

1.047g/ml / 0.998g/ml = 1.049 (the "OG" of my wort)

Bit of a phaff, but no question of accuracy (provided the weighing scales are good). This is what a hydrometer saves you (i.e. not me) from! I'll repeat the process for "FG" (no silliness converting to allow for alcohol content) and meantime one of those Tilt thingies is on duty monitoring progress (you think a pycnometer is a phaff? Then do not go near a "Tilt"! You even have to pay a premium to have one of them do your head in).

 

[strange-steve]

I drop a lead washer into a sample, if it floats then I know the OG is about right.

 

[lancon]

I've just had a "brewday", and the pycnometer was in action. I'll give a brief summary so anyone interested can give it a go. (And I can look up this post up next time to remind me what to do!). If it looks too complicated for you, ignore it; don't tell me it's too complicated 'cos I'm not interested.


Brew into fermenter. A small sample (30ml) removed at near enough 20C. Pycnometer bottle filled (there's nothing to line up, no concerns about meniscus, no microscopic "scales" to read) and weighed. I know the weight of the empty bottle and it's precise volume. So I now know the weight of the sample (grams) which divided by the volume (millilitres) gives me the wort's density.

45.89gms - 18.28gms (empty bottle weight) = 27.61gms (weight of sample)
27.61gms / 26.37mls (volume of bottle) = 1.047g/ml (density of sample)

The density looks like an SG, but not quite there yet. The density of pure water at 20C is 0.998g/ml (look it up on t'Internet). Divide density of wort (at 20C) by density of water (at 20C). The water density is the "reference", in scientific circles the water would be at 4C (close to 1.000g/ml).

1.047g/ml / 0.998g/ml = 1.049 (the "OG" of my wort)

Bit of a phaff, but no question of accuracy (provided the weighing scales are good). This is what a hydrometer saves you (i.e. not me) from! I'll repeat the process for "FG" (no silliness converting to allow for alcohol content) and meantime one of those Tilt thingies is on duty monitoring progress (you think a pycnometer is a phaff? Then do not go near a "Tilt"! You even have to pay a premium to have one of them do your head in).

How do you measure the volume of the bottle and no meniscus!?!?

 

[peebee]

How do you measure the volume of the bottle and no meniscus!?!?

The stopper has a hole in it (a capillary tube). Like this (measuring the SG of isopropyl alcohol here to prove it really is 99.9% pure - SG was 0.786 using a 4C reference, i.e. divide density of sample by 1.000, 'cos all the tables are created with laboratory or scientific hydrometers):

The meniscus in a capillary tube is of no significance. The kooky stopper is what makes the bottle a "pycnometer", though some fancy ones have built in thermometers (quite un-necessary for this application).

The bottle was filled with pure water at known temperature (and known density from the lookup tables on t'Internet) to give volume, which you only do once per pycnometer (I have 3, 1 spare 25ml one in case of breakage and one 10ml which I don't think the weighing scales will be accurate enough for - haven't tried yet).

 

[peebee]

The beer I was measuring earlier (OG 1.049) is about finished. The "Tilt" hydrometer is recording 1.018-1.019 but that seems a bit high (Tilts do go wonky after a few days in the fermenter). Seems a good time to test the 10ml pycnometer.

I know it's volume (10.62ml) and its weight (12.33g). A sample of the "finished" beer (at 19C, but close enough to 20C) in the bottle weighs 10.81g which divided by the bottle's volume gives a density of 1.018g/ml. The wort's density divided by water's density at 20C gives the SG … 1.019½-1.020. Hum, so the Tilt was okay. A quick check with the refractometer returns 1.017-1.018 (unclear muddy line to read). Why would I trust the refractometer? Because I recalibrated it to match the OG! The "wort correction factor" that came out of calibration (Beersmith) was 1.04 and I've seen that number quoted before which provides some confidence. The "wort correction factor" allows for the difference between the refractometer's native BRIX (a scale for sucrose) and the wort's predominantly "maltose" makeup. But as fermentation proceeds, the sugar concentrations change, and therefore the "wort correction factor" must change (sugar in finished beer is predominantly maltotriose and other dextrins, not maltose or sucrose). Can't be significant? Else there would be plenty of whinging.

This thread is playing havoc with my ideas of what a refractometer can tell me, never mind a hydrometer.

The figures from this 10ml pycnometer bottle are drifting apart, as I'd expected. So I'll stick to 25ml bottles unless some even better weighing scales emerge. Shame?

 

[gingerneil]

Tilt is good, but not sure what it gives you the open-source ispindel for about the third of the price ?