Hydrometer

[peebee]

…
They are both labelled with a calibration temperature of 60 degF, so they probably originated in the USA …

Ha! You'd think so wouldn't you. But our own scientific community wont let go of their 60F (16C, or 15.56C) calibrated hydrometers despite "standards" suggesting they should use a 4C standard (for the "reference" water sample - it gets complicated!). But brewing in the UK should be using 20C calibration (and 20C for the reference).

Want to know more? And an alternative to fragile hydrometers, or refractometers and their inconvenient scales drawn up for sucrose solutions: How accurate is your hydrometer?!!

 

[paintingken]

I was thinking about those turkey baster type things. The wine thief's didn't always seem too great to me any how.

buddsy

Every time I put my wine thief in my hot wort I think 'I wonder at what temperature this glass may break and ruin my beer'
I'm sure it's fine.
Turkey baster is going on my shopping list!

 

[peebee]

Every time I put my wine thief in my hot wort I think 'I wonder at what temperature this glass may break and ruin my beer'
I'm sure it's fine.
Turkey baster is going on my shopping list!

Watch which one you get! I got a glass one and chipped the nozzle off in no-time.

 

[paintingken]

Watch which one you get! I got a glass one and chipped the nozzle off in no-time.

Ouch, definitely going baster!

 

[peebee]

Ouch, definitely going baster!

Ah, I should have been clearer. I meant a glass baster! But as it seems you'll be giving glass a wide berth anyway, I guess I didn't need to pen the warning.

 

[Hop_it]

Ha! You'd think so wouldn't you. But our own scientific community wont let go of their 60F (16C, or 15.56C) calibrated hydrometers despite "standards" suggesting they should use a 4C standard (for the "reference" water sample - it gets complicated!). But brewing in the UK should be using 20C calibration (and 20C for the reference).

Want to know more? And an alternative to fragile hydrometers, or refractometers and their inconvenient scales drawn up for sucrose solutions: How accurate is your hydrometer?!!

Interesting . . . . . There is no doubt that a hydrometer calibrated to be read at 20degC would be more convenient, but it's no big deal to apply the temperature correction to the result from a 60degF hydrometer.
I had also thought about buying a pycnometer - not least because they are accurate (subject to weighing accuracy), and you only need a relatively small sample. I may well revisit that idea

 

[starseeker]

I use a plastic turkey baster to take samples during and at the end of fermentation . . . . . I have been told that they are occasionally used for other non-food related applications as well

You don't want to get the beer pregnant :)

 

[Hop_it]

I bought two plastic hydrometers covering different ranges from Beer Hawk a few years ago, but unfortunately they appear to have now stopped selling homebrew kit. They are made from polycarbonate (PC), so are very tough and durable. They are both labelled with a calibration temperature of 60 degF, so they probably originated in the USA. I can recommend them, so it might be worth searching further afield.
I also use a cheap refractometer, for checking fermentation progress because you only need a tiny sample. However, I would not rely on it for a final FG reading (and subsequent ABV calculation) because the reading you get is influenced by the alcohol content. There are conversion tables and calculators available on the web, but they are not very reliable.

I just had a look at my two plastic hydrometers mentioned above. If it helps, the brand name is "Herculometer". One of them has a range from 1.000 to 1.070, and the other has a range from 0.980 to 1.020. The calibration on both of them was a little bit out when I tested them in pure water (read 0.998), so it is necessary to adjust all reading up by +0.002. But that is not really unusual for "homebrew grade" hydrometers. The only other option is to pay a lot for scientific grade glass hydrometers . . . . . . . and then cuss like hell when you break one !!!!
I made a quick Google search for them. Amazon UK lists them as out of stock, but they do appear to be available in the USA.

 

[peebee]

Purely for the sake of disseminating interesting snippets ...

But brewing in the UK should be using 20C calibration (and 20C for the reference).

Relative Density (SG) is the ratio of a sample's density and a reference's density (hence no units of measurement, it's a ratio). So if a sample's density (sample being water) is 0.998g/ml @20C, and the reference's density (also water @20C) is 0.998g/ml, the SG is 0.998/0.998 which is 1.000.

"0.998" is a coincidence, nothing to do with preceding post.

The density of water at 4C is near enough 1.000g/ml. So a 20C calibrated hydrometer which is calibrated for a 4C water reference will measure 0.998/1.000, so the SG will be 0.998. The hydrometer is a "density hydrometer".

You are now nodding sagely, or utterly confused (like me!).

 

[Hop_it]

Purely for the sake of disseminating interesting snippets ...


Relative Density (SG) is the ratio of a sample's density and a reference's density (hence no units of measurement, it's a ratio). So if a sample's density (sample being water) is 0.998g/ml @20C, and the reference's density (also water @20C) is 0.998g/ml, the SG is 0.998/0.998 which is 1.000.

"0.998" is a coincidence, nothing to do with preceding post.

The density of water at 4C is near enough 1.000g/ml. So a 20C calibrated hydrometer which is calibrated for a 4C water reference will measure 0.998/1.000, so the SG will be 0.998. The hydrometer is a "density hydrometer".

You are now nodding sagely, or utterly confused (like me!).

OK, I see where you are coming from . . . . . . Yes, I agree that the density of water does vary with temperature, although not by very much within the range that is of interest to homebrewers, i.e. ~15 to 20 degC. But what I was trying to say (albeit not very clearly) is more simplistic than that. So, in the interests clarity, and the further dissemination of interesting snippets:

• My hydrometers are calibrated/designed to read an accurate relative density (SG) at 60 degF/15.56 degC
• Therefore the SG of pure water should read 1.000 at that temperature (If anybody is interested, the actually density is apparently 0.99907g/cc at 15.6 degC)
• The reading on both of my hydrometers was 0.998
• This means that the graduated scales are not quite in the correct position, i.e. there is an offset of 0.002
• I have assumed that the graduations on the scale are correctly spaced (because I have no way to prove or disprove this)
• So, I apply that offset (0.002) to all measurements within the range of that hydrometer

Phew . . . . I feel so much better now

 

[peebee]

...

Yeap! That is why I included the line "'0.998' is a coincidence, nothing to do with preceding post.".

Density of water @20C is 0.998 which could cause folk to confuse my post as relating directly to yours.

Your hydrometers will include a "second calibration", hidden from any reference in the instructions or on the hydrometer, that it's scale refers to a "water reference" at 60F. So at 60F (15.6C) it should read water as 0.999/0.999 or 1.000. A hydrometer reads "relative density" (SG) so always has that second calibration even is it doesn't mention it anywhere. Otherwise, what is it "relative" to?

 

[Hop_it]

Yeap! That is why I included the line "'0.998' is a coincidence, nothing to do with preceding post.".

Density of water @20C is 0.998 which could cause folk to confuse my post as relating directly to yours.

Your hydrometers will include a "second calibration", hidden from any reference in the instructions or on the hydrometer, that it's scale refers to a "water reference" at 60F. So at 60F (15.6C) it should read water as 0.999/0.999 or 1.000. A hydrometer reads "relative density" (SG) so always has that second calibration even is it doesn't mention it anywhere. Otherwise, what is it "relative" to?

Yes, I had realised where you got the 0.998 figure from. I think that I may have given you the impression that I did not fully understand the difference between density and relative density. This was probably not helped by quoting you in my explanatory post. I should have sent it as a stand alone message. I only wanted to make it clear where my figure of 0.998 came from, and that it is necessary (or at least desirable) to correct all readings for the offset (whatever it may be). I suspect that a lot of people do not check this when they buy a new hydrometer