AHB Articles: Using a Bulk Priming Calculator

[appius]

This is the discussion topic for article: Using a Bulk Priming Calculator

 

[Wolfy]

Might I suggest that (after asking the appropriate authors) someone looks to host the Bottle & Bulk Priming Calculator page on the AHB server rather than with Geocities?
Countless time's I've followed what should have been useful links to mass-hosting services like Geocities only to find them missing.
If permission was obtained, it would be nice to 'future proof' the article by hosting the subject of discussion locally.

 

[mash head]

I have used this resource from another web site unsure where but its in my favourites if someone needs to know. It stuffed me up as new brewer at the time I was un aware that american gallons wernt the same as what I thought a gallon was ie 4.5 litres so my beer came out way under carbonated even worse was that it was a style that had low gas any way. Dont use one any more just prime up to my own preferances.
Greg

 

[Sammus]

Or use beersmith...

 

[buttersd70]

Or use beersmith...

Which still has the same inherent issue as an external calculator; that being, end user fault due to using the wrong temperature in the calculations (most commonly, people using the temperature of their cold conditioning beer, as opposed to the temperature required for the calculation of residual CO2).

Beersmith has the added issue in relation to volume, in that it works off of the batch volume going into the fermenter, not going into the bottles (or priming vessel), and doesn't account for any post-ferment losses to trub/yeast, or due to transfer in the event of racking. Although, it is easy enough to just convert the beersmith figure to a g/L amount, and then apply that to the actual volume being bottled.

 

[Sammus]

Yeah I just meant in regards to the program, not the article.

The temperature 'problem' is still there no matter what you use to calculate. In Beersmith you just type in the beer volume, temp and required CO2, so I'm not sure what you mean about the volume issue.

That online one in the article though does have options for sucrose and two different versions of DME (not sure which one we use...), which I guess might be handy for some. The Beersmith one gives force carb pressure and DME and Dextrose.

 

[buttersd70]

The temperature 'problem' is still there no matter what you use to calculate. In Beersmith you just type in the beer volume, temp and required CO2, so I'm not sure what you mean about the volume issue.

Ahh, I see. You were referring to the carbonation tool, I was referring to the carbonation section in the recipe view.

AFAIK, as far as the dme is concerned, they've just hedged their bets on the fermentability, cos it varies brand to brand. So it would be a slight case of trial and error to get it right with dme.

 

[ianh]

Hi All

My understanding is that sucrose is made of one glucose molecule and one fructose molecule bound together. Fructose follows the same metabolic pathway as glucose and can thus be considered equivalent, so the calculations proceed the same way as for pure glucose.

But glucose is sold as the monohydrate and thus you need to add 15% to the weight. Thus to my mind there should be a 15% difference in weight between the weight of sucrose and glucose for a certain CO2 level.

The geocities bulk prime calculator link from the AHB article for 2.4 volumes CO2, at 20C and 23 litres gives values of 142 g glucose and 135 g sucrose, not a 15% difference.

Would appreciate it someone can point out where I have gone wrong as I use these calculations as part of my spreadsheet. Values from the spreadsheet are 142 g glucose and 123 g sucrose.

Thanks

Ian

 

[ianh]

Hi All

My understanding is that sucrose is made of one glucose molecule and one fructose molecule bound together. Fructose follows the same metabolic pathway as glucose and can thus be considered equivalent, so the calculations proceed the same way as for pure glucose.

But glucose is sold as the monohydrate and thus you need to add 15% to the weight. Thus to my mind there should be a 15% difference in weight between the weight of sucrose and glucose for a certain CO2 level.

The geocities bulk prime calculator link from the AHB article for 2.4 volumes CO2, at 20C and 23 litres gives values of 142 g glucose and 135 g sucrose, not a 15% difference.

Would appreciate it someone can point out where I have gone wrong as I use these calculations as part of my spreadsheet. Values from the spreadsheet are 142 g glucose and 123 g sucrose.

Thanks

Ian

Anyone

 

[ianh]

This is the discussion topic for article: Using a Bulk Priming Calculator

I think the calculator calculates the amount of sucrose required incorrectly and it should be the dextrose weight less 15%

cheers

Ian

 

[buttersd70]

Ian,
That is assuming a 15% differential between glucose, and dextrose monohydrate. Other sources state that the difference is actually 9%, ie dextrose is 91% fermentable. The majority of the priming calculators use figures based on the work of Michael Hall, in Brew By The Numbers. Halls work is contradictory to that of Hibberd (whose article you mentionioned earlier). Hall calculates volumes of CO2 using the 0C reference, Draper and Hibberd use 20C. This is why Halls numbers are used, as a volume of CO2 is defined as one litre of co2, in solution, in 1 litre of beer at 0C.

Halls numbers are used in just about every online priming calculator, at least all of the ones that I've seen; they are also used in various brewing software. I'm not going to dispute the numbers given in the calculators themselves; that is up to the authors of those particular calculators. Nor is that the purpose of the article, which serves soley to advise the unwary as to what variables are required to be entered to use a calculator correctly (particularly in relation to the calculation of the residual CO2, due to the dozens of posts continually asking "do I enter the temperature that the beer will be served at?"; or, "do I enter the temperature that the beer is, given that it is coming out of cold conditioning? Do I warm my beer up before priming? " etc, etc).

Given that the difference in the carbonation between 123g and 135 grams, over a 23L batch, equates to just over 0.1 volumes of CO2, I see it as an academic argument anyway; particularly given the tolerence and accuracy of measurement, for the sugar itself, and, more importantly, for the specific volume of liquid to be carbonated, and the temperature achieved during fermentation (and the timing of that temperature, relevant to the cessation of CO2 production from the fermentation itself). There are already so many approximations in the process, anyway.

 

[ianh]

Ian,
That is assuming a 15% differential between glucose, and dextrose monohydrate. Other sources state that the difference is actually 9%, ie dextrose is 91% fermentable. The majority of the priming calculators use figures based on the work of Michael Hall, in Brew By The Numbers. Halls work is contradictory to that of Hibberd (whose article you mentionioned earlier). Hall calculates volumes of CO2 using the 0C reference, Draper and Hibberd use 20C. This is why Halls numbers are used, as a volume of CO2 is defined as one litre of co2, in solution, in 1 litre of beer at 0C.

Halls numbers are used in just about every online priming calculator, at least all of the ones that I've seen; they are also used in various brewing software. I'm not going to dispute the numbers given in the calculators themselves; that is up to the authors of those particular calculators. Nor is that the purpose of the article, which serves soley to advise the unwary as to what variables are required to be entered to use a calculator correctly (particularly in relation to the calculation of the residual CO2, due to the dozens of posts continually asking "do I enter the temperature that the beer will be served at?"; or, "do I enter the temperature that the beer is, given that it is coming out of cold conditioning? Do I warm my beer up before priming? " etc, etc).

Given that the difference in the carbonation between 123g and 135 grams, over a 23L batch, equates to just over 0.1 volumes of CO2, I see it as an academic argument anyway; particularly given the tolerence and accuracy of measurement, for the sugar itself, and, more importantly, for the specific volume of liquid to be carbonated, and the temperature achieved during fermentation (and the timing of that temperature, relevant to the cessation of CO2 production from the fermentation itself). There are already so many approximations in the process, anyway.

Thanks for that Butters

It helps clear up some of the misunderstanding. I used a 15% difference in my spreadsheet and someone queried the values. I was aware of dextrose 91% fermentability but the difference in the referenced calculator is about 5%. As you say it equates to just over 0.1 volumes.

I will leave the spreadsheet as is for the time being. Should there be a need for a stand alone Bulk Prime spreadsheet I could easily create one.

cheers

Ian

 

[buttersd70]

yeah, a lot of the problem is that there are multiple sources, using different calculations, to try and get to the same end goal. It's a similar thing that is found with bittering, when comparing the differing formulae.

Different sources leading to different outcomes, due to different suppositions at various parts of the calculations, unfortunately, leads to confusion, as often as not. One of the great things about brewing, is that one persons work often supercedes anothers, with adjustments, revisions, and recalculations, based on prior knowledge. All too often, apples are compared to oranges, instead of to apples. You can only really go so far in your own work before you find the need to start relying on the prior studies of others, and taking the leap of faith that they are correct in their assumptions and calculations. Otherwise it would drive you round the bloody twist. :lol:

edit....re the difference between the 9% and the 5%.....I looked up multiple sources on that, and couldn't work out why, in each case, they were saying 9, but using 5......slightly odd. But the difference between 9 and 5 is even less than that of 15 and 9.....and after checking calculator after calculator (I must have looked at at least a dozen, just this afternoon), they all come to the same result (for your example, to the gram). So I can only bow to the weight of opinion.

 

[ballzac]

From a tangent in this thread: http://www.aussiehomebrewer.com/forum//ind...view=getnewpost

The amount of CO2 already in solution is dependent on temperature, so if your brew was cold when you bottled, it will give you higher carbonation than if it was hot.

My understanding is that it should be based on the maximum temperature of the beer once fermentation is nearing completion.

A smarter man than I wrote an excellent and comprehensive article about this topic: linky

Hadn't heard that before. Interesting link. I don't know if that information is based on empirical evidence, or just theory, but the theory seems flawed to me. The fermenter, contrary to the claim, is under pressure (roughly 15 PSI). I don't see why this pressure should be discounted when you consider what a dramatic effect an extra 15 PSI will do to the quantity of dissolved CO2 in the beer.

There is a thick blanket of CO2 on the beer, and moreso when the temperature has been raised and more has come out of solution. Surely when the temperature drops (given enough time) this will go back into solution? I don't see what would prevent it from being redissolved.

EDIT:Of course, "given enough time" is an important point, because if it takes a week for the CO2 to go back into solution, but you chill over 24 hours and then bottle, the highest temp (or close to) should be used anyway.

Sorry if I've read your post incorrectly ballzac, but there is no way there is 15psi of pressure in the fermenter. The reason the wort/beer wont absorb any of the previously de-absorbed (yes, Iknow thats not a word but I can't think of the term ATM) co2 is because there isn't enough pressure in there, at a guess I'd say it would be sweet FA more that atmospheric pressure, probably not even a measurable difference.

HB79, Ballzac is being technically correct. 15 psi is equivalent to 1 atmosphere of pressure. This is the "strenuous" pressure we live under each and every day.

Now, as to it contributing to re-absorbtion of the CO2 layer back into the beer, I'll call BS, but am open to reasoned, well argued debate.

I was thinking he was saying 15 psi as in more pressure than a standard keg when carbed. Thanks WB

Yep. That's what I meant. And sorry for going off-topic to an extent, but I just want to give my reasoning. The pressures normally used in kegging are actual gauge pressures. That is, they are stated as quantities above atmospheric pressure. So when you have your keg pressurised at '15 PSI', this is a gauge pressure, and actually means that there is about 30 PSI in the keg. If a keg is under this pressure at 15C, about 2 volumes of CO2 should be dissolved in the beer when it is saturated (I got this from one of the carbonation spreadsheets). If the temperature is dropped to 2C, and the pressure kept constant, the volumes of CO2 should increase to 3 (given time, perhaps a week?).

It seems to me that the same principles should be at work at atmospheric pressure, which is not negligible, but is half the absolute pressure that I was referring to in the kegging scenario, unless there is a reason that it shouldn't. I too am quite open to the idea that my argument is flawed, but a 'hunch' isn't enough to convince me . Of course, if this process takes a week or something in a keg, it would possibly take even longer at half the pressure. This means that if you have a beer that fermented at 20C and then quickly chill prior to carbonation, it will make FA difference. But what if you were lagering (in a CO2 purged lagering tank) or some other similar scenario? It could make a real difference to the amount of dissolved CO2, so it is an important point to get right.

Perhaps an experiment is in order

 

[ballzac]

Thanks for your eplanaition on your reasoning ballzac. Makes sense to me now what you meant. I still don't believe that under normal fermenter conditions that co2 would re-absorb, think of it this way, if it's coming out of solution at 15psi, then wouldn't it need to be higher for it to re-absorb, regardless of the temperature? Would be a little different in a purged keg I spose, if you left it pressurised but not hooked up to the gas, it would eventually reach equilibrium and absorb some of it. Sorry for even further

PV=NRT
So in some ways, a decrease in temperature is equivalent to an increase in pressure (over-simplified I know).

Yes there is 15psi on the top of the beer in the fermenter, but there is also 15psi on all outsides of the fermenter effectively meaning no pressure difference.

It's the same as in a keg, but in a keg the pressure is provided by the rigidity of the steel. The most important thing, as far as I can gather, is the pressure at the interface of the beer and CO2.

EDIT: This discussion really belongs in the discussion topic for the wiki article, I'll copy it from here and we can continue it there.

 

[pcmfisher]

Are we talking a sealed container or a fermenter with an airlock here?

 

[ballzac]

Just a fermenter with an airlock. It is still under pressure though. The difference in pressure is not important. In a keg, the pressure gradient only occurs within the steel anyway. The pressure within the beer is still constant (ignoring the 1PSI or so difference at the top and bottom of the beer). If you had a pressure gradient within the beer, you would have flow.

 

[pcmfisher]

So if you took the lid of your fermenter would it still be under pressure?

 

[ballzac]

So if you took the lid of your fermenter would it still be under pressure?

Of course.

 

[ballzac]

So anyway, someone in the other thread politely pointed out that PV=NRT isn't really the relevent equation here.

Henry's Law is the relevant equation. I haven't studied chemistry (my major was in theoretical physics), so I'm only going on my interpretation of the wikipedia artice. Would be great if someone with some chemistry knowledge chimed in . According to wiki, the amount of dissolved gas in solution is directly proportional to the partial pressure of the gas. If we make the debatable assumption that the concentration of CO2 in the headspace at the interface is close to 100%, then the partial pressure is equal to atmospheric pressure. If this is the case, then half the pressure (e.g. atmospheric pressure as opposed to 15PSI gauge pressure) means half the concentration (e.g. 1 volume CO2 as opposed to 2 volumes).

Thoughts anyone?