Hydrometer, correct use

[user 55733]

Sorry if this is in the wrong section.

Can someone explain how to use these properly.

I want to know how to relate the figures to alcohol content.

Thanks

Jungle

 

[Pappers_]

Hi Jungle. You take a hydrometer reading when you first put the wort in your carboy or fermenter. Use the scale that reads like a thermometer. Then when your beer is all done becoming beer, take another hydrometer reading. The difference tells you how much sugar was eaten up by the yeast, producing alcohol. Some folks here figure that by hand, I put it into brewing software (I use Beersmith).

 

[Revvy]

The formula for determining that, that pappers wusses out and uses beersmith for is, og-fg x 131 = %ABV. (That's probably the extent of my math ability to figure out.)

 

[Revvy]

And this video is the best I've seen to explain how to use it, it's also by one of our own Bobby M.

 

[remilard]

The correct way to use a hydrometer:

1. Get the sample at the reference temperature (probably 60 F, should be printed on the hydrometer somewhere) and degassed.

2. Read at the meniscus.

This will give you the relative density of the wort at the beginning and end of fermentation which doesn't really tell you much about the alcohol content (for that you need starting and finishing extract) but you can make some assumptions and get pretty close using the formulae referenced above.

 

[user 55733]

Thanks for the replies and posts guys. I'm doing n investigation at uni using different sugars, and the hydrometer is the only apparatus we have access to.

 

[Revvy]

Thanks for the replies and posts guys. I'm doing n investigation at uni using different sugars, and the hydrometer is the only apparatus we have access to.

It really is the only apparatus you need.

 

[maida7]

1. Get the sample at the reference temperature (probably 60 F, should be printed on the hydrometer somewhere) and degassed.

If the temp is not exactly 60F you can adjust the reading to compensate. Even within 10 degrees of 60 and the reading will be fairly close. here is a link for adjusting the readings for temp. http://hbd.org/cgi-bin/recipator/recipator/hydrometer.html

 

[remilard]

If the temp is not exactly 60F you can adjust the reading to compensate. Even within 10 degrees of 60 and the reading will be fairly close. here is a link for adjusting the readings for temp. http://hbd.org/cgi-bin/recipator/recipator/hydrometer.html

It's correct use to measure at the reference temperature, it may be acceptable to read at other temperatures and apply an adjustment.

If the goal is determining alcohol content based on relative density readings, you are already layering estimates on estimates, why make it worse?

 

[maida7]

It's correct use to measure at the reference temperature, it may be acceptable to read at other temperatures and apply an adjustment.

If the goal is determining alcohol content based on relative density readings, you are already layering estimates on estimates, why make it worse?

I guess I'm just not that anal about what the alcohol is. I brewed for many years without using a hydrometer. I still made great beer. I do use one now but I'm not so hung up on being super accurate with it. If my readings are off by .001 then I'm OK with that.

 

[ajdelange]

Sorry if this is in the wrong section.
Can someone explain how to use these properly.

For best accuracy, obtain a set of narrow range hydrometers. They are often sold in sets of 3 (low, medium and high density) and are made for vintners. If possible, get ones calibrated for beer as the surface tension has an effect on the reading. That not withstanding I get excellent (0.1 °P) agreement with much more elaborate equipment.

The hydrometer should be scrupulously clean and dry. The test jar should be too but if it is wet you can always rinse with sample a few times.

The sample should be at the reference temperature specified by the hydrometer's manufacturer.

Fill the jar with sample to near the top. Then lower the hydrometer gently into the sample to a bit above where you think it will come to rest. The jar should be full enough so that some sample overflows (think about where you do this - i.e. not over mum's Persian rug). This is a great way to deal with foamy samples as the foam goes off with the overflow. Now let the hydrometer settle for a minute or 2.

Read the meniscus either at the top or bottom according to the manufacturers directions.

I want to know how to relate the figures to alcohol content.

Balling determined years ago that 2.0665 grams of extract produced 1 gram of alcohol, 0.9565 g of CO2 and 0.11 g yeast biomass - on average. From this basic piece of information various formulae for estimating the alcohol content have been devised. Balling's own is

ABW = f*(p-m) where f is a multiplicative factor, p is the "original extract" i.e. the extract before fermentation began and m is the "apparent extract" at the end of fermentation. p is simple the original hydrometer reading (in °P) and m is the hydrometer reading (also in °P) at the end. Most good hydrometers read in °P and even the cheap ones tend to have a Plato scale on them. This is sometimes labeled "Brix" but the Brix and Plato scales are so close that this doesn't matter. If your hydrometers are only labeled in specific gravity you can convert to Plato using p = -616.868 + 111.14*s - 630.272*s*s + 135.997*s*s*s where s is the apparent specific gravity measured at 20 °C and referenced to 20 °C.

The factor, f, varies with OE and is well approximated by f = 0.39661 + 0.0017091*p + 1.0788E-5*p*p. For nominal strength beer (12 °P) f = 0.4187.

No now you have ABW as a percent. If ABW is sufficient you are finished but if ABV is wanted to have to convert ABW to ABV using the formula

ABV = ABW*s/0.791 with s being the specific gravity of the beer and 0.791 that of pure ethanol.

If you have only °P markings on your hydrometer you will need to convert °P to s. You can get that from s = 1 + 0.00386777*p + 1.27447*p*p + 6.34964E-8*p*p*p.

I put in all this detail because you mentioned doing this at the uni and I supposed, therefore, that some degree of precision was wanted.

One last thing that might be helpful is that °P represent the number of grams of sugar in 100 grams of solution. I mention this because this makes it very easy to make up a solution of given strength. Tare a beaker, add 10 grams of sugar, add water to 100 grams. Presto, a 10 °P sugar solution.

Thanks

Jungle[/QUOTE]

 

[maida7]

yeah what he said

 

[remilard]

I guess I'm just not that anal about what the alcohol is. I brewed for many years without using a hydrometer. I still made great beer. I do use one now but I'm not so hung up on being super accurate with it. If my readings are off by .001 then I'm OK with that.

I'm not that anal either but this guy asked for correct methods and he appears to be doing experiments. If he wanted to use a hydrometer to make good beer I would suggest that if he use it well enough to get with half a degree plato that is probably fine.

 

[DrJerryrigger]

I've been using a bic pen with some lines drawn on in. I can read it to an accuracy of about + or - 15 point... which is about the accuracy of tasting it. I really need to get something better... like a coffee stirring straw, with a small rock glued to it...

 

[ajf]

And for nit pickers, the formula quoted by Revvy shoud be (og-fg) x 131 = %ABV.

-a.

 

[funkswing]

It's correct use to measure at the reference temperature, it may be acceptable to read at other temperatures and apply an adjustment.

If the goal is determining alcohol content based on relative density readings, you are already layering estimates on estimates, why make it worse?

EDIT: it isn't linear.......my bad.

.....So you aren't making estimates by reading at x F. When I get my mash runnings I know that I can basically just add 0.020 to the number. If I want to be exact, I meas. the temp, then correct the value to the calibration temp. (using Promash). This doesn't make it any less accurate.

People should calibrate your hydrometer in just water (DI is best, but if you have soft water that is fine too) before use. My first hydrometer was dead on (0.000 @ 60 F), but I broke that one and my new one reads 1.002 at 60 F, so I subtract 0.002 from all my readings.

 

[ajdelange]

The density of wort/beer is linear within the temperature range that you use for brewing.

It's definitely not linear (http://www.pbase.com/image/129020575) but I suppose it could be considered close enough to linear over a few degrees.

 

[GilaMinumBeer]

the most common use is for a mid brewday distraction and excercise in patience and temperment as we proceed to sweep the remaining shards into the corners while concocting absurb ways to float the salvaged scale into or beloved wort while quietly pondering the nature of metals used as the ballast that are now sunken in the depths of our greatest effort or scattered across the floor.

 

[maida7]

just orders myself a refractometer!

 

[remilard]

The density of wort/beer is linear within the temperature range that you use for brewing. So you aren't making estimates by reading at x F. When I get my mash runnings I know that I can basically just add 0.020 to the number. If I want to be exact, I meas. the temp, then correct the value to the calibration temp. (using Promash). This doesn't make it any less accurate.

It is definitely less accurate because promash is making an assumption about the composition of your wort.

The correct method is at the reference temperature.

If there is a separate thread for good enough use of a hydrometer I can change my tune.

 

[DrJerryrigger]

It's definitely not linear (http://www.pbase.com/image/129020575) but I suppose it could be considered close enough to linear over a few degrees.

It's even less linear than that graph implies, water is most dense at about 4.1deg C, therefor less dense above and below that point. I don't know off hand, but a believe it does something more complicated near boiling too.

 

[ajdelange]

It's even less linear than that graph implies, water is most dense at about 4.1deg C, therefor less dense above and below that point. I don't know off hand, but a believe it does something more complicated near boiling too.

Didn't think anyone would care about that low and that high but here's the picture from 0 - 100°C. This time I included water and plotted density (so normalize by whatever you want if you are interested in SG.

http://www.pbase.com/image/129027288

I guess the ultimate reflection on the linearity or lack thereof is that the data in the curves are taken from the ICUMSA polynomial which is 4th order in both concentration and temperature (though not all 80 coefficients are non 0).

 

[user 55733]

For best accuracy, obtain a set of narrow range hydrometers. They are often sold in sets of 3 (low, medium and high density) and are made for vintners. If possible, get ones calibrated for beer as the surface tension has an effect on the reading. That not withstanding I get excellent (0.1 °P) agreement with much more elaborate equipment.

The hydrometer should be scrupulously clean and dry. The test jar should be too but if it is wet you can always rinse with sample a few times.

The sample should be at the reference temperature specified by the hydrometer's manufacturer.

Fill the jar with sample to near the top. Then lower the hydrometer gently into the sample to a bit above where you think it will come to rest. The jar should be full enough so that some sample overflows (think about where you do this - i.e. not over mum's Persian rug). This is a great way to deal with foamy samples as the foam goes off with the overflow. Now let the hydrometer settle for a minute or 2.

Read the meniscus either at the top or bottom according to the manufacturers directions.



Balling determined years ago that 2.0665 grams of extract produced 1 gram of alcohol, 0.9565 g of CO2 and 0.11 g yeast biomass - on average. From this basic piece of information various formulae for estimating the alcohol content have been devised. Balling's own is

ABW = f*(p-m) where f is a multiplicative factor, p is the "original extract" i.e. the extract before fermentation began and m is the "apparent extract" at the end of fermentation. p is simple the original hydrometer reading (in °P) and m is the hydrometer reading (also in °P) at the end. Most good hydrometers read in °P and even the cheap ones tend to have a Plato scale on them. This is sometimes labeled "Brix" but the Brix and Plato scales are so close that this doesn't matter. If your hydrometers are only labeled in specific gravity you can convert to Plato using p = -616.868 + 111.14*s - 630.272*s*s + 135.997*s*s*s where s is the apparent specific gravity measured at 20 °C and referenced to 20 °C.

The factor, f, varies with OE and is well approximated by f = 0.39661 + 0.0017091*p + 1.0788E-5*p*p. For nominal strength beer (12 °P) f = 0.4187.

No now you have ABW as a percent. If ABW is sufficient you are finished but if ABV is wanted to have to convert ABW to ABV using the formula

ABV = ABW*s/0.791 with s being the specific gravity of the beer and 0.791 that of pure ethanol.

If you have only °P markings on your hydrometer you will need to convert °P to s. You can get that from s = 1 + 0.00386777*p + 1.27447*p*p + 6.34964E-8*p*p*p.

I put in all this detail because you mentioned doing this at the uni and I supposed, therefore, that some degree of precision was wanted.

One last thing that might be helpful is that °P represent the number of grams of sugar in 100 grams of solution. I mention this because this makes it very easy to make up a solution of given strength. Tare a beaker, add 10 grams of sugar, add water to 100 grams. Presto, a 10 °P sugar solution.

Thanks

Jungle

[/QUOTE]

Thanks for your time to post that, and it is exactly what I need and yu have saved me alot of work, I thank you!

Do you know where I could find that infomation so I can reference it?...I don't think the University would allow me to reference homebrewtalk!

 

[remilard]

Thanks for your time to post that, and it is exactly what I need and yu have saved me alot of work, I thank you!

Do you know where I could find that infomation so I can reference it?...I don't think the University would allow me to reference homebrewtalk!

[/QUOTE]

I think the Balling formulae are in Fix's books.

 

[funkswing]

Jungle - I'm glad you got the info you needed, I didn't realize you were meas. for something other than homebrewing.

Back to that chart: I was wrong, it obviously isn't linear, but how does that make correcting for temperature unacceptable (for brewing?). If you look at that chart for the 7.5 brix and 15 brix, the difference from 0 C to 100 C for both gravities is maybe 0.001 SG, and that is the range from freezing to boiling, which is of little concern when taking OG on brew day.

Of course you are all right, but that chart hasn't convinced me that correcting for temperature is going to produce invalid results, even when considering diff. gravity beers.

How does "promash is making an assumption about your wort" play any significant role in correcting for temp when reading a hydrometer for OG?

 

[ajdelange]

The information on how to read a hydrometer can be found in A Textbook of Brewing by Jean De Clerck, translated by Kathleen Barton-Wright, Chapman and Hall, London, 1958, Vol II pp17. The info on Ballings formula can be found in the same source at pp 426 - 429. De Clerck has tablulated values for f. The formula I gave for it is a fit to the tabulated data. I did the fit so you will have to reference HBT if you need to reference that.

The formula for conversion of s to p is the "ASBC polynomial". It is found in the Methods of Analysis of the ASBC published by the ASBC, 3340 Pilot Knob Road, St. Paul, MN, USA. This formula comes from a fit to the Plato tables (apparent 20°C/20°C specific gravity of sucrose solution vs concentration in grams sucrose per 100 grams of solution i.e. °P). The inverse formula (compute s from p) was determined by me by fitting the ASBC tables using s as the independent variable. s can always be found from p by interpolation into the ASBC tables or by inverting the ASBC polynomial which can be done in closed form.

The ABV from ABW formula comes from common sense. If you have x grams of ethanol in y grams of solution of density_beer then you have x/density_ethanol cc of ethanol in y/rho cc of solution i.e. ABV = (x/density_ethanol)/(y/density_beer). Dividing each of the densitites by the density of water at some reference temperature converts the densities to specific gravities without changing the value of the fraction thus
ABV = (x/s.g._ethanol)/(y/s.g._beer) = (x*s.g._beer)/(y*s.g._ethanol) = (x/y)*(s.g._beer)/(s.g._ethanol) = ABW*s.g._beer/0.791.

 

[ajdelange]

If you look at that chart for the 7.5 brix and 15 brix, the difference from 0 C to 100 C for both gravities is maybe 0.001 SG, and that is the range from freezing to boiling, which is of little concern when taking OG on brew day.

I think you've stuck in an extra 0. At 15 Bx the 20°C density is 1.05916. At 100°C it is 1.0169 for a difference of 0.0423.

Of course you are all right, but that chart hasn't convinced me that correcting for temperature is going to produce invalid results, even when considering diff. gravity beers.

No problem with correction if it is done right. I've learned, however, to be skeptical of things posted on websites and written up in magazine articles.

How does "promash is making an assumption about your wort" play any significant role in correcting for temp when reading a hydrometer for OG?

Promash makes 2 assumptions. The first is that all "extract" is sucrose which, of course, it isn't. But this assumption also underlies the ASBC tables. The second assumption is that the ratio of the densities of wort at 2 different temperatures is the same as the ratio of the densities of pure water at those same 2 temperatures. This turns out to be a pretty good assumption.

 

[funkswing]

So, what would be the best way to make temp. corrections?

I've decided I will meas. the SG both hot and at ref. temp for my next few brews (at diff. gravities of course!) to see how much of a diff. I can notice.

The first one (brewed Friday) was dead on with a gravity of 1.057, meas. at 125 F and 60 F.

 

[ajdelange]

We could debate what the "best" method is. In such cases one often simple reverts to the "official" method which, in this case, would be the ASBC's correction method. This involves looking up the correction in a table but the table only goes up to 26°C which is their gentle way of telling you that if you don't cool down to laboratory temperature you should at least cool to 26°C (78.8 °F). OTOH the table goes down to 4°C so cooling below room temperature is apparently more acceptable than trying to measure hot wort. Makes sense, I guess. Plunging a room temperature hydrometer into boiling wort has got to be stressful.

The ASBC tables entries are in degrees Plato to be added to the reading of a Plato hydrometer referenced at 20 °C. The corrections in the table can be adequately approximated by corr = 0.04989*(T-20) +0.0011242*(T-20)*(T-20) + 0.00089981*(T-20)*P where T is the temperature in centigrade and P the wort concentration in °P.

If you insist on working at higher temperature I suppose I'd use the fact that water and sucrose solutions behave essentially the same way WRT density change and multiply the hydrometer reading at temperature T by the ratio of the density of water at 20C (998.203 g/L) to the density of water at T. Thus, for example, 20 °P wort at 80 °C has a density of 1.05237 (and true specific gravity relative to 20°C) of 1.05352. Presumably this is what a 20 °C hydrometer would read (ignoring the difference between true and apparent specific gravity which is too small to see on a hydrometer). The density of water at 80 °C is 971.785 g/L and the ratio of density of water at 20 °C to water at 80 °C is 1.02719. Multiplying this by the hydrometer reading gives 1.08411 for the estimated SG at 20 °C. The actual SG of a 20 °P sucrose solution at 20 °C is 1.08292 for a discrepancy of 0.001.

You can get water density (grams/L) from the polynomial
(((((-281.03006e-12*t +105.84601e-9)*t-46.241757e-6)*t-7.9905127e-3)*t+16.952577)*t +999.83952)/(1+16.887236e-3*t)
where t is the temperature in °C. Note that this is in a form which you can copy and paste into a spreadsheet after which you will either have to type in a cell number for each t or define the variable t to refer to the cell number containing the temperature. t is in °C.

 

[trubled]

i have read most of the posts and find them missing some points.

I have used a hydrometer many times on many days.

A couple pointers:
(a) to really get an accurate reading fill the test tube to the brim before putting in the hydrometer -- this removes the miniscus and inaccuracies associated with looking through plastic
--put something underneath to capture the displaced liquid

(b) place the hydrometer in carefully so not to displace the surface at the brim of the tube and spin it at the same time
-- on initial gravity readings the spinning is not so important but when your ferment is going there is lots of CO2 coming out of solution and gloming on to the hydrometer lifting it up and throwing off the reading. This is why spinning is important to throw off the CO2 connecting to the tool.

 

[trubled]

temp within reason isnt all that important because there is so much flux with the meter.
what is important is insuring CO2 isnt grabbing onto the instrument -- if this sounds wrong take your hydrometer and put it in a test tube full of half fermented beer and watch it rise a number of points.

 

[ajdelange]

CO2 can be adequately dealt with in fermenting beer by the use of a second cylinder somewhat larger than the hydrometer jar. Fill the second cylinder with more than it takes to fill the one that you will use for the measurement. Place your clean, dry hand (or other more suitable closure) over the jar and shake like mad. Open the closure just enough to let the gas escape, let the jar settle for a minute or 2 then repeat. Now pour the liquid into the smaller jar to near the lip. Then lower the hydrometer into the jar so it overflows as I described in an earlier post. If any foam remains, just blow it away. Then read. If you want a second reading some time after the first (after the sample has warmed, for example) bubbles will form on the body of the hydrometer. Just give the stem a spin in this case.

I have found I can read narrow range hydrometers on a gassy sample to an accuracy of 0.1 °P using this technique.