Why does anyone use a hydrometer?

[andyakameatloaf]

For those that don't:

Until this point, everything you said may as well have been written in Elvish to me.
And that's why I use a hydrometer.

 

[ScottM]

Not quite on the same level but I use a fairly complex FG calculation for when the sugar's are known. Obivously with grain brewing this is never going to be the case so it's fairly useless there, but when you know what you are putting into the brew... you can be fairly accurate with what will come out.

I wrote a massive post on it a while back but not a lot of people could see my angle so I just use it myself now.

The assumptions of my calculation are:

You know (or can work out) exactly how much fermentables are being added to your brew.
You know (or can work out) the exact yield of what you are adding.
You know the attenuation of the yeast (Higher attenuation effectively means the yeast is less fussy with it's sugar varieties).


When you have the above you can calculate the OG and the FG with reasonable accuracy.


The OG is simply all the weights and yields added up and then compared to the total volume.

total yield = total yield + (yield of ingredient/100*quantity of ingredient) (done for every ingredient then added)

OG = 1 + ((yield/volume)*0.00036) (the volume is in litres, hence all the 0s before 36, with 36 being the gravity of 100g of sugar in 1l of water)



The FG is a little more complicated as even though you can work out what the gravity will be minus the sugar, you need to take into account that alcohol is less dense than water and the resulting gravity also has to take this into account... as you mentioned (0.789)

total fermentability = total fermentability + (fermentability of ingredient/100*quantity of ingredient) (done for every ingredient then added)

FG = OG + 0.624 - sqrt((((100/(1000*volume)*(total fermentability*0.645))*0.789*(yeast attenuation/100*1.33))/100.3)-(OG-(125.65/200.6))^2+0.7817+OG^2-(OG*125.65/100.3));


UK standard for ABV is

ABV = (OG-FG)*(100.3*(OG-FG)+125.65)



Those are the calculations that I use to work out my recipes and they all come in VERY accurately. The standard FG calculation is simply 25% of the OG, which is only any good for brews with less fermentables (stouts, ales, etc). When making a light lager, cider or wine it's no use at all and absolutely miles out. Adding 2kg of sugar to 20L of water apparently has an FG of around 1.009 according to most calculators lol.

 

[anthonyUK]

For someone with an ounce of science knowledge that is a very stupid question with relation to brewing.

Don't hold back. Tell him what you really think.

Yeah sorry scheelings that was a bit harsh but given what was posted prior to yours I stand by what was said as opposed to how it was said.

 

[chojo]

I use a hydrometer because the man in the shop told me too, although i like the idea of a chimp with a blunt stick so can it can hit me every time i make a brew and remind me to take a damn reading!

 

[morethanworts]

Slightly OT, but ScottM - just interested...

Those are the calculations that I use to work out my recipes and they all come in VERY accurately.

...Have you tested any of your beer (or had it tested in a lab) to validate the calculations of alcohol content? I have no reason to doubt them - you've clearly looked much further into it than me, but it would be really interesting to know a calculation that has been tested on the resulting beer from someone who's done primary research.

I'm only a hearsay bio-chemist, when it comes to the science, I'm afraid!

 

[ScottM]

Slightly OT, but ScottM - just interested...

Those are the calculations that I use to work out my recipes and they all come in VERY accurately.

...Have you tested any of your beer (or had it tested in a lab) to validate the calculations of alcohol content? I have no reason to doubt them - you've clearly looked much further into it than me, but it would be really interesting to know a calculation that has been tested on the resulting beer from someone who's done primary research.

I'm only a hearsay bio-chemist, when it comes to the science, I'm afraid!

Wish I could lol. Na, don't know anyone that would be able to do the work for me and I don't really have the drive to get it checked out properly.

The calculation for ABV is the one that HMRC stand by (IIRC).

http://customs.hmrc.gov.uk/channelsPort ... _CL_000232

Section 30 :)

 

[alanywiseman.]

I you really care to Scott I am sure someone at Herriot Watt in Edinburgh would be able to. They run a brewing and distilling degree. All it would take is to run it through a gas chromatography system to get the results.

 

[morethanworts]

The calculation for ABV is the one that HMRC stand by (IIRC).

Likely to work out on the high side, then :lol:

 

[Pawlo7671]

The lesson is, just use a hydrometer. They cost feck all and at the end of the day you can't simply assume all sugars have been fermented, less you like bottle bombs of course then go right ahead !! But no, seriously, buy and use a hydrometer.

 

[ScottM]

I you really care to Scott I am sure someone at Herriot Watt in Edinburgh would be able to. They run a brewing and distilling degree. All it would take is to run it through a gas chromatography system to get the results.

Not really that fussed to be honest, I judge the ABV with how many bottles it takes me to fall over lol. I just use the calculations as estimates. The FG calculation was just something I wanted to explore, as a kind of exercise. I do these things just to keep the ole noggin ticking :)

The calculation for ABV is the one that HMRC stand by (IIRC).

Likely to work out on the high side, then :lol:

Surprisingly the ABV from that calculation is actually lower than other calculations that I have seen. They might have missed a trick there

 

[Russ146]

For what its worth i never use one

To me its an unnecessary risk of contamination. I leave to ferment for 14 days at a constant temperature and transfer to a barrel. I'm now on my 20th kit with 100% success.

I then leave for at least 4 weeks and i make premium pub quality beer again and again.

As somebody said K.I.S.S it, you know it makes sense

 

[BarnsleyBrewer]

When the chemistry is more accurate? (assuming all sugar is fermented)

For those that like Chemistry:

C12H22O11 + H2O + invertase => 2 C6H12O6

C6H12O6 + Zymase => 2 C2H5OH + 2 CO2

So 1 mol of sucrose yields 4 mols of ethanol.

Molar mass of sucrose = 342.30 g/mol (based on molecular weight)
Molar mass of ethanol = 46.06844 g/mol

Therefore 342.3g of sucrose, yields 184.273 g of ethanol

Or more conveniently, every 100g of sugar, yields 53.8g of ethanol

The density of ethanol is 0.789 g/cm³
1L ethanol = 0.789*1 => 0.789KG

Therefore 53.8g of ethanol = 68.23 millilitres of ethanol

This volume can be assumed to be produced for every 100g of sugar added as long as the alcohol threshold remains below the theoretical upper limit of the yeast.

For those that don't:

So every 1kg of sugar added to a 30 litre brew, increase the alcoholic content by 2.22%.

WoW, do you know all this or is it a cheeky Copy & Paste?? :whistle: :whistle:

 

[scheelings]

I will be getting a hydrometer with my new kit - so i'll have to learn how to use it.

So I have a question regarding the stuck fermentation people are talking about. Is that the result of very cold temperatures? When I was in Brisbane it seemed that fermentation took 3 days tops - but in summer even at night it didn't drop below 20 degrees C.

Where I am now it never gets below 25 degrees never mind the season. I think unless I get an electric chill pack for the fermenter - I better stick with things like ginger beer rather than traditional beers..

 

[scheelings]

Can you tell the alcohol content from the final reading only?

For someone with an ounce of science knowledge that is a very stupid question with relation to brewing.

Yes, I recognize the arrogance of my original post.

I think I could spend months just reading everything already posted here and just try to learn.

I'm overwhelmed with the number of responses I'm getting, the sheer amount of knowledge on this forum and how active it is. I really think I'm going to like it here.

 

[bunkerbrewer]

Not quite on the same level but I use a fairly complex FG calculation for when the sugar's are known. Obivously with grain brewing this is never going to be the case so it's fairly useless there, but when you know what you are putting into the brew... you can be fairly accurate with what will come out.
...
The assumptions of my calculation are:

You know (or can work out) exactly how much fermentables are being added to your brew.
You know (or can work out) the exact yield of what you are adding.
You know the attenuation of the yeast (Higher attenuation effectively means the yeast is less fussy with it's sugar varieties).
...
FG = OG + 0.624 - sqrt((((100/(1000*volume)*(total fermentability*0.645))*0.789*(yeast attenuation/100*1.33))/100.3)-(OG-(125.65/200.6))^2+0.7817+OG^2-(OG*125.65/100.3));

Interesting stuff, I like a bit of maths and I'm constantly finding ways to make my brewing spreadsheet more complicated :)

I've probably misunderstood, but the above assumptions sound a little bit circular to me? You're calculating the FG, but how do you know the attenuation of the yeast unless you measure the FG? I keep a record of attenuation for each brew, and it's rarely the median of the stated range.

 

[anthonyUK]

No probs scheeling.
I'm all for testing accepted practise but as with science it has to have repeatable evidence.
Without it we wouldn't have had BIAB for example.

I hope you continue to ask questions that encourage discussion as this is what forums like this are best at, using the diverse experiences and knowledge of otherwise unrelated people to expand on their area on interest :

 

[Hawks]

For what its worth i never use one

To me its an unnecessary risk of contamination. I leave to ferment for 14 days at a constant temperature and transfer to a barrel. I'm now on my 20th kit with 100% success.

I then leave for at least 4 weeks and i make premium pub quality beer again and again.

As somebody said K.I.S.S it, you know it makes sense

Until you get a stuck ferment, bottle it and that movement is enough to kick the yeast back into action. :nono:

No need to risk infection - I trust mine to finish so I don't check 3 days running anymore - when I am ready to keg I run some beer into a trial jar and check it BEFORE it gets bottled or kegged. Knowing my OG ( again a hydrometer needed here ) and the expected attenuation I can see if it's finished.

 

[graysalchemy]

+

Yes, I recognize the arrogance of my original post.

I think I could spend months just reading everything already posted here and just try to learn.

I'm overwhelmed with the number of responses I'm getting, the sheer amount of knowledge on this forum and how active it is. I really think I'm going to like it here.

Sorry If I was a bit cutting before but we see to many smart alecs on here who are trying to reinvent the wheel, it gets a little tiresome. This forum is a wealth of knowledge with numerous professional brewers and some extremely knowledgeable and experienced homebrewers, all willing to pass on their knowledge.

So basically read listen and learn we are friendly bunch who want to help new people in our chosen vocation.

:thumb: :thumb:

 

[scheelings]

Sorry If I was a bit cutting before but we see to many smart alecs on here who are trying to reinvent the wheel, it gets a little tiresome. This forum is a wealth of knowledge with numerous professional brewers and some extremely knowledgeable and experienced homebrewers, all willing to pass on their knowledge.

So basically read listen and learn we are friendly bunch who want to help new people in our chosen vocation.

:thumb: :thumb:

No offence taken and I recognize that I'm the kind of individual the needs an occasional kick when I get a bit too enthusiastic.

I hope that at some point I could meet a few of you and sample some of the various brews - I take it most posters here are from the UK?

 

[graysalchemy]

Yes we are and usually once you get to know us and make some friends someone will be up for a bottle swap :thumb: