# How long to force carb: The calculator



## damoninja (5/10/16)

Hi everyone, 

I've scoured around looking for a utility that calculates approximately how long it will take you to carbonate your beer at a specific temperature and pressure. 

I managed to find plenty of resources which listed just pressure and temp, managed to find one which did calculations at 40 PSI only, which is OK for some things... So I had a bit of spare time and made one in excel. I've taken some trusted commonly referenced resources and worked out what the differentials and exponents are within a reasonable margin.

You can input the style of beer you're brewing and it will give you an idea of how long it should take to carbonate and gives a (good?) guide of the range you'll hit over time. 

It's new so it might have some bugs or need some improvement, download it and let me know what you reckon and how it compares to your experiences and knowledge. 

I can't upload it because it's a macro enabled excel file (a few basic functions) so I've dropped it in my google drive

Here is the link to it


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## damoninja (5/10/16)

h34r: reserved h34r:


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## BKBrews (5/10/16)

Mate, I have no idea about this stuff, so if that's accurate then I think it is very, very good. I was wondering how I would do all of this when I set my keezer up, but it looks like if I set my temp at 2 degrees and leave it at 10psi (serving pressure for all of my kegs) for 12 - 14 days, it will be ready to go at 2.4 volumes.


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## BrewedCrudeandBitter (5/10/16)

As a terrible brewer who only just kegged a beer for the first time a couple of weeks ago this is incredibly helpful.


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## pcqypcqy (5/10/16)

Nicely done. Time is a factor that's often missing from these things, and is obviously the most important variable. I wonder how much goes into the calculation of the rate at which the gas dissolves given the other variables. Seems to me that a first principles calculation would be reasonably straight forward. But then I'm a structural engineer and a not a chemist, so I'm sure there's more to it.

I've been thinking of putting something like this together, so you've saved me the effort.


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## damoninja (5/10/16)

As far as accuracy goes - I've used this well known chart to get the total CO2 numbers for given PSI, I did edit it somewhat as that chart does have errors in it *gasp* it looks like it was entered manually so there are some typos or duplicates, I've used calculations for all mine. 

For time, I used a combination of things, but the main source was some spreadsheet I found that calculated time required to carb at 40PSI at a specific temperature, I was able to break down how much CO2 would be dissolved per day and adjust. 

The potential room for error is - there are some assumptions... such as absorption rates over time being linear which is almost certainly not the case toward the end of carbonation, that's really the main thing which may make it less accurate... the biggest pitfall of this is likely at higher levels where it may actually carbonate faster in an inverse slope opposed to linear. 

If anyone has any insights here please feel free to critique


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## Droopy Brew (5/10/16)

Looks like it has the makings of a very useful tool mate well done.

Do you intend to create a drop down box for beer style? At the moment it is only Pale ale which I assume is there for test work.


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## pcqypcqy (5/10/16)

damoninja said:


> As far as accuracy goes - I've used this well known chart to get the total CO2 numbers for given PSI, I did edit it somewhat as that chart does have errors in it *gasp* it looks like it was entered manually so there are some typos or duplicates, I've used calculations for all mine.
> 
> For time, I used a combination of things, but the main source was some spreadsheet I found that calculated time required to carb at 40PSI at a specific temperature, I was able to break down how much CO2 would be dissolved per day and adjust.
> 
> ...


The rate is almost certainly proportional to the difference between the applied pressure (i.e. regulator setting) and the volumes already dissolved. Things only flow when there is a difference in pressure, and as this difference drops so does the flow rate. 

Your spreadsheet is locked, so I can't see how the calculations are done, but you should be able to use the dissolved pressure from the previous time step as an input for the next time step to account for this.


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## damoninja (5/10/16)

That's is a drop down already, there's something like 90 styles or you can go to the bottom and give a specific number if you want


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## damoninja (5/10/16)

pcqypcqy said:


> The rate is almost certainly proportional to the difference between the applied pressure (i.e. regulator setting) and the volumes already dissolved. Things only flow when there is a difference in pressure, and as this difference drops so does the flow rate.
> 
> Your spreadsheet is locked, so I can't see how the calculations are done, but you should be able to use the dissolved pressure from the previous time step as an input for the next time step to account for this.


Yeah I get you - I think that will be a V2 enhancement while I figure out the best way to work this out... the source I used to determine amount of CO2 per absorbed per hour was linear so I kept things this way. 

It's semi complicated, but I've used the linear hourly volume of CO2 dissolved at 40PSI (for the temp chosen), divided by 40 and multiplied by the PSI that's been entered. Then apply that hourly until it reaches the max, once it's reached max it no longer increases. 

So the way it currently is removing the previous amount dissolved amount would totally negate the next number, or making it based on the previous value alone would make it an infinite curve and never reach the actual target (maybe doesn't matter when we're only talking a few weeks though).

*Edit:* I reread what you meant and reckon I get you... say if I'm set to 10PSI, and at X hour, 10% of the max potential 2.6 vols has been absorbed, I want to deduct 10% of my pressure... so I'll only absorb 90% of what I did in the last interval... Hmmmmmmmm!

Agree though I need to make that component proportional in some way and certainly plan to


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## pcqypcqy (5/10/16)

A very rough way of doing it is to assume that it takes 2 weeks for any (reasonable) beer to get carbonated using a set and forget method. You can then work out the linear rate over this time, and then come up with a factor based on the volumes already dissolved and those left to dissolve to simulate the fact that an asymptotic curve is steeper at the start (i.e. faster rate of dissolution) and flatter at the end (slower rate).

Have a look at the attached sheet for an example.

I came up with an initial steepness factor of 6 times the linear rate to give a relatively stable pressure by the end of two weeks.

This sheet only mimics the asymptotic nature of the problem though, the target volume, assumed time to get there, etc are all static values.

What I'd really like is a calculator that can predict for a given time period, temperature and regulator setting, how many volumes will have dissolved in that time - i.e. not the equilibrium volume but a time dependent one. Then, you can come up with a force carb regime where you set to say 20 psi for 4 days (or as many pressure/time steps as you want) and get close to your target volume. I'm going to do some reading on the chemistry involved and try to come up with a calc in excel that mimics this process from first principles. I might then do some measurements maybe (somehow, haven't thought this through) to calibrate it. 

View attachment carbonation over time.xlsx


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## moonhead (5/10/16)

Nice work, I like the simplicity and immediate feedback on the chart.

Next step is to get some kind of accuracy with the CO2 pressure I'm putting into my kegs.


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## peteru (5/10/16)

Does the size of the area where gas meets liquid play a significant role in the rate of carbonation? For example, upright keg vs keg on it's side, or 4L (tall) vs 5L (wide) mini-kegs.


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## pcqypcqy (5/10/16)

peteru said:


> Does the size of the area where gas meets liquid play a significant role in the rate of carbonation? For example, upright keg vs keg on it's side, or 4L (tall) vs 5L (wide) mini-kegs.


You are right, the instantaneous rate would have to depend on the area. The long term rate would also depend on the volume of beer you are carbonating.


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## mckenry (5/10/16)

That's great. Can you do one with a carb stone? Typically a day is all it takes to reach equilibrium. So, much faster than absorbing from headspace. Would be nice to know exactly though and I think you're the man [emoji12]


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## damoninja (6/10/16)

peteru said:


> Does the size of the area where gas meets liquid play a significant role in the rate of carbonation? For example, upright keg vs keg on it's side, or 4L (tall) vs 5L (wide) mini-kegs.


Yes but I've written in the notes it's for carbing a normal old 19L keg  too many variables to consider. 




mckenry said:


> That's great. Can you do one with a carb stone? Typically a day is all it takes to reach equilibrium. So, much faster than absorbing from headspace. Would be nice to know exactly though and I think you're the man [emoji12]


If someone has something that says what the absorption rate is versus not having a carb stone I could probably add that in, assume it would basically be a multiplier...


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## damoninja (6/10/16)

pcqypcqy said:


> A very rough way of doing it is to assume that it takes 2 weeks for any (reasonable) beer to get carbonated using a set and forget method. You can then work out the linear rate over this time, and then come up with a factor based on the volumes already dissolved and those left to dissolve to simulate the fact that an asymptotic curve is steeper at the start (i.e. faster rate of dissolution) and flatter at the end (slower rate).
> 
> Have a look at the attached sheet for an example.
> 
> ...


Good stuff, that's what I was thinking in a way

Few queries though: 

1. Why a slope factor of 6? Very natural number and seems to apply in this instance but wondering if this was just what felt right? 
2. Would we expect the absorption rate per interval to be linear with increasing PSI? Eg hr 1 @ 12 PSI = 0.044642857 - does 24 PSI = 0.089285714 (double)?

Either way it's a great idea, seems like something you're enjoying so wouldn't wanna steal the concept but I think the two would go hand in hand and reckon it would be a useful tool to have along side this one, so more than happy for them to live in the same sheet if you wanna collab on it


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## pcqypcqy (6/10/16)

damoninja said:


> Good stuff, that's what I was thinking in a way
> 
> Few queries though:
> 
> ...



I arrived at 6 by playing around with different values of the initial steepness so that it 'looked right' on the chart, i.e. a quick initial jump in dissolved CO2, with a fairly steady curve by the end of the two weeks. much lower and it will still absorbing co2 at the end, and any higher and it's fully carbonated in a day, neither of which seemed right. But this is all just guess work.

My understanding that is that it would be linearly proportional to _difference_ in pressure, so not quite what you've assumed.

Happy to collaborate, I get a bit of downtime at work at the moment in front of the screen just waiting for things to come in, so I'll be looking at this in more detail in the next few days. I'm also thinking about how to test it, this is my plan so far:

fill a keg
apply a certain pressure for a certain time
unhook the gas, leave it for a day (or longer?) to reach equilibrium
measure the headspace pressure using a gauge (maybe a pressure gauge with a barb, a short bit of hose, and a gas disconnect)
record this value,
reapply pressure for another time step
repeat
This should give some data points along the way to calibrate the spreadsheet model.


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## pcqypcqy (6/10/16)

mckenry said:


> That's great. Can you do one with a carb stone? Typically a day is all it takes to reach equilibrium. So, much faster than absorbing from headspace. Would be nice to know exactly though and I think you're the man [emoji12]


Carb stones work by increasing the surface area between gas and beer. I would hate to think of the calculations involved, might be best to measure it as I've described above.

Though if it only takes a day, then you probably don't need to worry too hard? Unless you're an OCD type like myself who just wants to know...


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## damoninja (6/10/16)

pcqypcqy said:


> I arrived at 6 by playing around with different values of the initial steepness so that it 'looked right' on the chart, i.e. a quick initial jump in dissolved CO2, with a fairly steady curve by the end of the two weeks. much lower and it will still absorbing co2 at the end, and any higher and it's fully carbonated in a day, neither of which seemed right. But this is all just guess work.
> 
> My understanding that is that it would be linearly proportional to _difference_ in pressure, so not quite what you've assumed.
> 
> ...


Sounding like a plan, certainly seems like a V2 enhancement


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## Lyrebird_Cycles (6/10/16)

pcqypcqy said:


> A very rough way of doing it is to assume that it takes 2 weeks for any (reasonable) beer to get carbonated using a set and forget method. You can then work out the linear rate over this time, and then come up with a factor based on the volumes already dissolved and those left to dissolve to simulate the fact that an asymptotic curve is steeper at the start (i.e. faster rate of dissolution) and flatter at the end (slower rate).
> 
> Have a look at the attached sheet for an example.
> 
> ...


It's a basic log curve.

The rate of change of concentration is proportional to the difference between the present concentration and the equilibrium concentration

d[CO2]/dt = k ( [CO2]eq - [CO2]t )

[CO2]eq is a constant for a given set of conditions, let k [CO2]eq = A, so the equation becomes

d[CO2]/dt = A - k[CO2]t 

The solution to a differential where the rate of change varies with the output is always an exponential or a log curve (in natural logs), if the sign is negative it's a log curve.

If you can generate the data required, I can write the equation you need, Excel handles logs quite well.

BTW the model you are proposing is covered by Fick's Law, so the other factor you might want to include is viscosity, diffusion rates at liquid / gas interfaces are known to be dependent on liquid viscosity. The reason for this is that if the gas molecules move from the absorbtion surface slowly (high viscosity), this creates a higher surface concentration which reduces the effective concentration difference between gas and surface.


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## pcqypcqy (6/10/16)

Lyrebird_Cycles said:


> It's a basic log curve.
> 
> The rate of change of concentration is proportional to the difference between the present concentration and the equilibrium concentration
> 
> ...


Not familiar with Fick's Law (I'll read up on it) but the reading I've done so far talks about Henry's Law quite a bit. 

I found this article that helps explain the process a little. Doesn't include time as a factor, but it does predict the equilibrium volume of dissolved gas as a function of regulator pressure, temperature, final gravity, alcohol content, etc.

http://www.vitalsensorstech.com/PDF's/Methods%20of%20Analysis%20for%20correcting%20CO2%20content%20for%20Specific%20Gravity%20and%20Alcohol%20November%202011.pdf

I'm a bit of an excel junky myself (engineer), so I'll have a go at generating some data and fitting a curve to it and working back to a predictive model, then share it here. Might take a while but I'll update as I test new kegs.


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## Lyrebird_Cycles (6/10/16)

Henry's Law governs the [CO2] at equilibrium with a given pressure at a temperature, Fick's Law governs the route by which it gets there.

True story: I used to do some design work for a company that did alcohol reduction in wines using a membrane process. One of the principals had done as you suggest and spent some weeks developing a predictive model of membrane flux which occupied over a thousand rows of a spreadsheet.

One day he showed me the spreadsheet and the data: it took me less than half an hour to reduce the entire spreadsheet to a single equation. He was a little peeved.


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## GABBA110360 (6/10/16)

I use the kiss principle
300 kpa for 24 hours seems to get to the right area @about 4 deg c


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## damoninja (6/10/16)

GABBA110360 said:


> I use the kiss principle
> 300 kpa for 24 hours seems to get to the right area @about 4 deg c


For some, yeah... Just poured the one I kegged yesterday at about 8pm at about 2C, 40PSI... I'd say it's about 70% there, it's a bit under what I'd normally take it at... rather than leave it overnight again I've pulled it back to ~15 PSI I'll pull back to about 12-13 once it's where I want it. 

But - it's a lot more carbed than I really expected... and I have left kegs at 40 PSI for 2-3 days and got good carb levels before

So, pcqypcqy is on to something... the falloff *needs* to be taken in to consideration for this to be go from a good tool to an awesome tool


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## pcqypcqy (7/10/16)

Lyrebird_Cycles said:


> Henry's Law governs the [CO2] at equilibrium with a given pressure at a temperature, Fick's Law governs the route by which it gets there.
> 
> True story: I used to do some design work for a company that did alcohol reduction in wines using a membrane process. One of the principals had done as you suggest and spent some weeks developing a predictive model of membrane flux which occupied over a thousand rows of a spreadsheet.
> 
> One day he showed me the spreadsheet and the data: it took me less than half an hour to reduce the entire spreadsheet to a single equation. He was a little peeved.



But I'm an engineer, I actually ENJOY playing with excel.


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## Lyrebird_Cycles (7/10/16)

OK, excel away to your heart's content.

It would be interesting to see how well we agree at the end. I spent a few minutes playing with this and I came up with:

[CO2]t = [CO2]eq ( 1- e(-k * Tabs * t)).

A k value of around 0.002 seems a reasonable fit to your curve.

[CO2]eq is the equilibrium CO2 concentration, given by [CO2] = Pabs*e(2617.25/Tabs) * 0.00075/(352.5 - ABV)

[CO2] is in g/l

t is time in days

Tabs in K, just use oC + 273.15

Pabs in kPa, use Pgauge + MSLP/10



Edit: the equilibrium CO2 equation I've used is slightly different from the one I've used in the past, I modified it to take account of the lesser solubility of CO2 in the presence of remnant wort solids.


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## Lyrebird_Cycles (7/10/16)

GABBA110360 said:


> I use the kiss principle
> 300 kpa for 24 hours seems to get to the right area @about 4 deg c


The equation above gives 4.66 g/l CO2 for those conditions, is that about what you get?


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## pcqypcqy (7/10/16)

Lyrebird_Cycles said:


> OK, excel away to your heart's content.
> 
> It would be interesting to see how well we agree at the end. I spent a few minutes playing with this and I came up with:
> 
> ...


not following why you divide the mean sea level pressure by 10 when calculating the absolute pressure?


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## Lyrebird_Cycles (7/10/16)

Because MSLP is given in hPa by BOM.

Sorry I should have made that clear, unfortunately too late to edit.


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## Lyrebird_Cycles (7/10/16)

I just realised I ignored the CO2 left from fermentation. The equation above starts from zero.

New version where [CO2] at start is [CO2]o:

[CO2]t = [CO2]o + ([CO2]eq - [CO2]o) *( 1- e(-k * Tabs * t)).

k will need to be adjusted to fit the curve, I just had a play with a remnant CO2 value around 1.8 and k = 0.0014 seems to work OK

Simplified approximation: look up the equilibium CO2 and the remnant CO2 in standard tables. Call the remnant CO2 figure "start" and the difference between equilibrium CO2 and remnant CO2 "difference"

[CO2]t = start + difference * ( 1- e(t/2))

where t is time in days.


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## pcqypcqy (7/10/16)

Lyrebird_Cycles said:


> Because MSLP is given in hPa by BOM.
> 
> Sorry I should have made that clear, unfortunately too late to edit.


Gotcha, I had already put it in as 101.3 kPa and couldn't see why I should divide by 10 when all the units were the same 

For reference, I put some numbers through both your calc and the calc based on the paper I linked to earlier. For 5% beer at 12psi gauge pressure, your equation gives 2.531 volumes as the equilibrium pressure, and the other equation gives 2.51.


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## pcqypcqy (7/10/16)

you updated it just AFTER I'd put it into my spreadsheet 

Also I've just assumed STP for my conversion of your equation from g/l to vol/vol, I'll need to adjust this for the fridge temperature.

So my understanding of the limitations of this method so far are:

k is based purely on our anecdotal experience that it takes 2 weeks to reach a stable carbonation of around 2.5 volumes
the shape of the curve is based on our first principles understanding of the process involved, i.e. the rate at which the gas will dissolve in the beer is based on the difference between the 

I'm just wondering how to gather the data. After applying gas to the keg for a period of time, then removing the pressure and allowing that keg to reach that equilbrium, what does the headspace pressure actually tell us? From reading through stuff on Henry's law, there's a dimensionless coefficient that is the ratio of dissolved gas pressure and the headspace pressure. For CO2 and water it's something like 80%. 

So roughly speaking, if I take a reading and have a stable 10psi in the headspace at a given point in time, I'll have 8 psi in the beer? Do I then look up the standard kegging charts and for 8psi and whatever temperature we're at, I read back what the volumes should be? 

(assuming all temperatures, gas pressures, etc are all at equilibrium after I've stopped applying more gas).


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## pcqypcqy (7/10/16)

I can't seem to make your equations work when doing it step by step.


[CO2]t = [CO2]eq ( 1- e(-k * Tabs * t)). 

This one gives a nice curve when plotted out using hourly steps, say.

[CO2]t = [CO2]o + ([CO2]eq - [CO2]o) *( 1- e(-k * Tabs * t)).

It DOES match the first one when you set [CO2]o = 0, but it doesn't match when I take [CO2]o as the value from the previous step. At small enough time steps, this should give an estimate of the CO2 that was dissolved in each time step, and when added to the previous step it should match the curve nicely, but for the life of me I can't see what I'm doing wrong.


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## Lyrebird_Cycles (7/10/16)

Edit:
If you do it stepwise, the time in the exponent must be the time step, not the total time.


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## Lyrebird_Cycles (7/10/16)

pcqypcqy said:


> I'm just wondering how to gather the data.


Borrow a Zahm meter or an Orbisphere DO2/ CO2 unit.


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## GABBA110360 (7/10/16)

Lyrebird_Cycles said:


> The equation above gives 4.66 g/l CO2 for those conditions, is that about what you get?


I don't know about the equation but that seems to work for my ales
the only time i'm interested in g/l is if i'm priming for bottling other than that if it's over carbed from forgetting about it or any over reason I just degas it too easy.


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## Lyrebird_Cycles (8/10/16)

For Damo and / or pcqy:

I'm assuming all the data you've collected is for an almost full Corny keg or similar.

As I see it, carbonation time will be dependent on fluid column depth so you'll get different results for vessels of different heights. I can't see why the relationship wouldn't be linear but some data would be good.


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## Zorco (8/10/16)

Lyrebird_Cycles said:


> OK, excel away to your heart's content.
> 
> It would be interesting to see how well we agree at the end. I spent a few minutes playing with this and I came up with:
> 
> ...



That's interesting, subscript on the superscript. ASCII Special? It handles like text. How did you do that LC?


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## Lyrebird_Cycles (8/10/16)

I can't take any credit for it: the edit window comes up with little subscript and superscript icons.

I can write ladder logic for PLCs, that's about the extent of my coding capabilities.


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## pcqypcqy (8/10/16)

OK, got the stepwise stuff working. Prelim numbers suggest 30 psi for 48 hours puts you at 2.5 volumes, then you set to your serving/long term equilibrium pressure. I'll play with this a bit more before sharing to make it neater and double check it's working correctly, probably will be Monday when I'm back at my work desk before I can do that.

Been thinking about the data collection, I'll find a spare dial gauge and barb fitting to screw it into, attach it with a short length of hose to a gas disconnect, then put this on as soon as I take the carbonation gas off the keg. Hopefully the volume within the gauge is negligible with respect to the headspace, and in any case if I let the keg reach equilibrium while the gauge is connected, then it shouldn't matter anyway. I can then watch that gauge to determine when equilibrium for that carbonation step has been reached.

Initially I'll just use fullish corny's as I'll test it on beer that I plan to drink. After christmas parties and case swaps are out of the way, I'll have a bit of spare keg capacity to maybe keg some half batches and gather that data as well.


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## pcqypcqy (8/10/16)

GABBA110360 said:


> I don't know about the equation but that seems to work for my ales
> the only time i'm interested in g/l is if i'm priming for bottling other than that if it's over carbed from forgetting about it or any over reason I just degas it too easy.


Just checking, Lyrebird is talking about g/L of dissolved CO2, I get the feeling you're talking about g/L of added priming sugar?


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## Lyrebird_Cycles (8/10/16)

You'll need to make a correction for the headspace volume anyway, just add any extra volume for the gauge to that and you'll be good to go.

Edit: this is in reply to #41 above.


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## pcqypcqy (8/10/16)

Another idea - would measuring the gas bottle weight with a set of scales do the trick? I'm thinking a set of commercial scales that could handle the weight of a full gas bottle, reg, etc, but still measure to the gram or less. 

I've seen these online for reasonable prices and I was thinking of getting one to calibrate the volumes on my sight glasses anyway.

if the equilibrium volume for 2.5 volumes is about 5g/litre, this should be measurable at the gram level for a full corny keg?


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## Lyrebird_Cycles (8/10/16)

As I see it measuring the gas bottle won't take account of the gas "blown off" when you equalise the pressure in the corny and any result could easily be thrown off by leaks.

If you can get reliable <1 g accuracy with a mass of around 30 kg, I *think* you could do it measuring the corny itself but you'd have to be very careful to exclude things like condensation.


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## damoninja (8/10/16)

Lyrebird_Cycles said:


> For Damo and / or pcqy:
> 
> I'm assuming all the data you've collected is for an almost full Corny keg or similar.
> 
> As I see it, carbonation time will be dependent on fluid column depth so you'll get different results for vessels of different heights. I can't see why the relationship wouldn't be linear but some data would be good.


Correct - that's in my list of assumptions

FTR - this thing is getting out of my depth / care care factor, I love excel to bits but usually use it for automation and data analysis using formulas for data manipulation opposed to equations. Some people get annoyed with people taking charge but I've got no issues with my sheet and calc becoming obsolete in the interest of better model.


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## GibboQLD (9/10/16)

zorsoc_cosdog said:


> That's interesting, subscript on the superscript. ASCII Special? It handles like text. How did you do that LC?


OT: It'll be the forum's stylesheets -- you can stack super/subscript with CSS as many times as you like, theoretically, and you'll still be able to copy/paste it like normal text.

Using the code below in an online evaluator will give you this, for example:






test
<font style="vertical-align: super;">test
<font style="vertical-align: super;">test
<font style="vertical-align: super;">test
<font style="vertical-align: super;">test
<font style="vertical-align: super;">test
<font style="vertical-align: super;">test
<font style="vertical-align: super;">test
</font></font></font></font></font></font></font>

And now, back to our regularly scheduled program...


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## pcqypcqy (10/10/16)

damoninja said:


> Correct - that's in my list of assumptions
> 
> FTR - this thing is getting out of my depth / care care factor, I love excel to bits but usually use it for automation and data analysis using formulas for data manipulation opposed to equations. Some people get annoyed with people taking charge but I've got no issues with my sheet and calc becoming obsolete in the interest of better model.


Yeah, sorry about that  You just happened to start the thread at the same time as I was looking into this myself AND had way too much spare time on my hands.

Here's the spreadsheet based on lyrebirds input.

It's not a pretty chart, but I'm guessing there are too many variables at play here to simplify it that much. 

Maybe we can think of some simple cases that are representative of what people do, like 24 hours at 40 or 30 psi, that sort of thing.

Inputs are all highlighted yellow, the rest should all be calculations or constants. 

View attachment carbonation over time2.xlsx


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## pcqypcqy (10/10/16)

Lyrebird_Cycles said:


> As I see it measuring the gas bottle won't take account of the gas "blown off" when you equalise the pressure in the corny and any result could easily be thrown off by leaks.
> 
> If you can get reliable <1 g accuracy with a mass of around 30 kg, I *think* you could do it measuring the corny itself but you'd have to be very careful to exclude things like condensation.


I might try a combination of methods. I want the scales anyway to calibrate my volumes, and I'm thinking about a kegmenter currently so if I get the spunding valve off that and pop it on the corny, should give me two methods to check without having bought anything specifically for it. If I adjust the spunding valve to have a high blow off pressure, theoretically it shouldn't blow off at all and the gauge will give me the headspace pressure.

The scales say they're precise to a gram, but at the price they're selling for I doubt it (around $50 from ebay). 

To get scales that can reliably measure 40kg to 0.1g though you're talking a few thousand dollars, so it's a bit of a jump.


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## damoninja (10/10/16)

pcqypcqy said:


> Yeah, sorry about that  You just happened to start the thread at the same time as I was looking into this myself AND had way too much spare time on my hands.


No sweat  just throwing it out there so it's clear no toes being stepped on


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## TheWiggman (10/10/16)

Any chance you could change the calculator so it deals with all SI units? (i.e. not PSI)


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## pcqypcqy (10/10/16)

TheWiggman said:


> Any chance you could change the calculator so it deals with all SI units? (i.e. not PSI)


Try this.

I'm normally a stickler for SI as well, but I've found that with nearly all the references for brewing are in US Imperial units that sometimes it's just easier to go with the flow. 

View attachment carbonation over time-si.xls


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## pcqypcqy (10/10/16)

damoninja said:


> No sweat  just throwing it out there so it's clear no toes being stepped on


If you want to give me an unlocked version of your sheet, I can use my model to update your charts with the curved increase over time (instead of linear as it is currently).


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## Liam_snorkel (28/11/16)

in SI too? That would be super.


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## pcqypcqy (28/11/16)

This fell by the wayside, but I'm thinking of doing some experiments soon. 

I'll use my threaded pin lock gas disconnect and a closed spunding valve to measure, then I'll force carb at some temp/pressure for some time, and then disconnect the gas, put the spunding valve on and wait for the head pressure to reach equilibrium. 

I'll then read the equilibrium pressure off the spunding valve gauge, and using the temperature read off a chart how many volumes were dissolved in that time step.

Not 100% accurate, but will give an indication of how the dissolved volumes changes with time.


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