homebrewandbeer.com

Hi everyone

Over the past week I have been putting togeather a spreadsheet to do calculations for me while I'm formulating recipes.

Now before you all go and say "hey Blandy, don't bother: just go and get Beersmith or QBrew or something," I have actually learned a lot on the way, and now I actually understand a lot more about the calculations this sort of software does, in stead of just putting numbers in, and magically some other numbers come out the other end with next to no understanding of how they got there.

I believe understanding the calculations, while not a substitute for having good technique and a "feel" for what's going to work, can be extremely valuable to a brewer and help them make beer even better.

also, it will help avoid arguments like this one:
http://www.homebrewandbeer.com/forum/vi ... highlight=
where we were all correct, but using different IBU scales .

Anyway, if anyone else is interested in sharing some equations, formulae, or tables of data they have found useful in making their recipes, how about we post them here?

Also, If anyone is curious how some things are calculated, post here and maybe someone else has already worked it out.

OK, I'll start with a favorite of mine (see above post)

IBUs

Palmer explains this extremely well (see link below), but I've given an example in metric units.
http://www.howtobrew.com/section1/chapter5-5.html

The "International Bitterness Unit" is a measurement of concentration of alpha acids in the beer, expressed in milligrams per liter.

factors affecting the IBU are:
- the mass (weight) of the hops (in grams)
- the percentage of alpha acids in the hops (%AA)
- the specific gravity of the boil
- the final volume of the batch (in litres)
- the time the hops are in the boil (in minutes)

the IBU is calculated like this:

IBU = (mass of hops) x (% Utilization) x (%AA) / [(boil volume) x 10]

where the percentage values are whole numbers (ie if you have %AA = 6.5%, use 6.5 for the calculation, not 0.065)
add the IBU contributions up if you have more than one hop addition.


The utilization is a function of boil time and boil SG, and represents the fraction of alpha acids in the hops that make their way into the wort.

this can be looked up on a table like the one in Palmer:
http://www.howtobrew.com/section1/chapter5-5.html
(you'll have to scroll down a bit, and multiply these figures by 100 to get the percentage values)

Utilisation values are highly variable depending on whose data you use. Palmer uses the Tinseth values, which is usually the default setting for most brewing software (I think).

However, if you are using another brewing manual, such as Papazian's "Complete Joy of Homebrewing," then you may use a different scale. It is therefore best to use just one scale and state which one you are using in your recipes.
(Papazian uses the Rager scale, which is much higher than Tinseth. for example, for a 45 min boil with SG = 1.070, the Rager value is 24%, and the Tinseth value is 17.7%)

formulae for Utilization are complicated, so tables are good unless you are doing a spreadsheet:

Tinseth: %utilisation = 165 x 0.000125^(Gb - 1)x[1 - e^(-0.04 x T)] / 4.15
where Gb is the boil SG, and T is the boil time
(see the link to Palmer)

for Rager:
% utilisation = (18.11+13.86*TANH((T-31.32)/18.27))
for a boil SG of 1.050 or less
if the boil SG is greater than 1.050, divide the above value by 1+(Gb-1.05)/0.2)
(source: http://www.realbeer.com/hops/FAQ.html#units)

now THAT'S why the tables are useful


------------------------------------------------------------------
so for an example (using the Tinseth scale):

if we have these hop additions:
40g of hop xyz AA = 7% boiled for 45mins
25g of hop zxy AA = 4% boiled for 15 mins
boil SG = 1.050
final volume = 20L

for the first contribution: Utilization = 21.2%
IBU1 = 40 x 21.2 x 7 / (20x10) = 29.7

for the second contribution: Utilization = 11.4%
IBU2 = 25 x 11.4 x 4 / (20x10) = 5.7

TOTAL IBU = IBU1 + IBU2 = 29.7 + 5.7 = 35.4
(Rager comes out at about 42)

If anyone can find some good formulae for bulk priming, that'd be super.

I've been using these:
http://oz.craftbrewer.org/Library/Metho ... uide.shtml
http://oz.craftbrewer.org/Library/Metho ... uide.shtml
http://www.geocities.com/lesjudith/Alco ... lator.html

but I'm after a formlar I can put into my spread sheet. Espectially one that can do the stuff the third link does (ie: required amount of sugar expressed as a function of temperature, desired level of carbonation, percentage of fermentable sugars in said sugar etc)

thanks,

Blandy

You can see the javascript source code for the calculator in that third link, just view the source of the page. Either have a look at it yourself or wait for me to convert it to an algorithm for you. I may never get around to that though.

um, right.

I'll look at it later. thanks rwh

OK, here's the priming equation for priming with cane sugar (sucrose):

according to the priming calculator at:
http://www.geocities.com/lesjudith/Alco ... lator.html

m = 3.22 x V x (CO2d - CO2r)

where:

m = mass of sucrose in grams
V = volume of beer in litres
CO2d = the desired volumes of CO2 in the brew
CO2r is the residual volumes of CO2 in the brew before priming

a good list of carbonation rates for CO2d, and a table of residual CO2 (CO2r) with respect to temperature can be found at:
http://oz.craftbrewer.org/Library/Metho ... uide.shtml

and here's a formular for residual CO2 with respect to temperature:

CO2r =(3.0378-5.0062*(10^-2)*(T*1.8+32)+2.6555*(10^-4)*(T*1.8+32)^2)
where T is temp in *C

this temperature is the temperature that the beer is at when you add the priming sugar.


PLEASE check these values. if you do a typo or something, you could end up with bottle bombs

meh....I gas up the keg until there's enuff bubbles innit!

Good work Blandy....does your "residual CO2" calcs also take into account the elevation at which you bottled the beer?!

Cheers,
TL

Unfortunately, no. It's just for sea level. Which will be OK for most people, but I'm sure there's quite a few high-altitude brewers out there that would have undercarbonated beer if they use that equation.

Also, I highly reccommend the VicBrew Recipes and Almanac. It's got loads of recipes and other useful stuff in it. It's got data on local produce and the like, such as descriptions on a lot of the grain that's available.
I picked it up at G&G the last time I was there for about $10

No probs - for the records, Farrer Ridge is 755m above sea level which may have a bearing on the results....but since I always brew here it's something that I can overlook!

Cheers,
TL