Friday, June 26, 2015

We interrupt this broadcast...

Yes, I know I still owe the third part of my series on partigyle, but I just had an interesting conversation that makes me want to write about something else for a moment: Kegging and carbonation.

Two friends of mine called me earlier with a question. One of them kegs his beers, and he had an odd problem: He can keep a sealed keg around for quite a while, but once he taps it, he only has about three days to finish it, or it will go bad. This happens consistently and regardless of the type of beer he kegs. I asked him what does it mean that the beer "goes bad", and he says that it becomes sweeter, heavier, and looses carbonation. I asked him to describe his process:

"I usually naturally carbonate my beer. That is, I put in the corn sugar the way I'd do with bottles, seal it, and put it a away for a bit. If I'm in a hurry I'd force carbonate. I'd put the keg on 30psi for a day and shake it, then 20, then 10. When it's carbonated I put it on tap at serving pressure of 6psi and serve it*."

"Well, there's you're problem" I responded. "In both methods in which you carbonate, you utilize higher pressure for carbonation than for serving. When you put beer on 6psi, the volume of gas dissolved in the beer will eventually equalize to the volume dissolved under that pressure, and the beer will become less carbonated"

Let me explain:
William Henry (source: wikipedia)
The physical relationship between pressure and carbonation is governed by something called "Henry's Law" **, which states:

 "At a constant temperature, the amount of a given gas that dissolves in a given type and volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid."

In laymen's terms this basically means that the more pressure of a gas you have over the liquid, the more of that gas will be dissolved inside the liquid and vice verse. Or to put it in even simpler terms: when you put beer under 20psi of CO2 it will be more carbonated (eventually) than beer that's under 10psi (at the same temperature). The two key phrases in that statement are "eventually" and "same temperature"

The easiest way to think about carbonation is to think of it as a finite amount of CO2 gas in a volume of beer. Think of beer before you carbonate it. It's completely "flat", but that doesn't mean it doesn't have any gas in it.  Rather, it has an amount of gas in it proportional to the amount of gas outside it. Doesn't really matter how much gas that actually is, just that this is our "baseline" amount of gas, so we'll call that 1 volume of gas.

Now if we want the beer to be carbonated, we want the volume of gas IN the beer to be more that the volume of gas OUTSIDE of the beer. We'll talk about how to do that in a second, but first let's just define our goal here. We want an amount X of gas in the beer that is bigger than 1 volume as we described above. For purpose of discussion let's say we want 2 volumes of gas***. That is we want twice as much gas in the beer as it had if it were not carbonated at all. So how do we get it?

Well, remember what I said were the important parts of Henry's law? "Eventually" and "Temperature". As it turns out, if you put the beer under a given amount of pressure at a given temprature for a given amount of time, it will reach the carbonation level you want. How do you know what pressure and temprature? Well, there's formulas for that. Or you could just use this handy chart from  This chart gives you a handy reference to what pressure to put your beer under at what temperature to get the results you want.***

So why did my friend's beer "go bad" after three days? Well, it didn't. What happened was that when my friend carbonated his beer, he carbonated it to his desired carbonation level, about 2.4 volumes. He then put it in a refrigerator that's probably about 40F at 6psi. A quick glance at the handy chart shows that under those conditions the beer would only dissolve 1.92 volumes. This didn't happen immediately, but eventually (remember "eventually"?) the amount of gas dissolved in the beer dropped from 2.4 down to 1.92. At that carbonation level, the beer appeared flat, and (because carbonation effect perceived body and flavor) sweeter/heavier. Putting the beer under the correct pressure for the carbonation level would solve his problem, and let him enjoy his beer for a lot longer.

* Actually, the man said he puts it on 6 bar, which rather amazed me. 1 bar is equal to 14.7 psi, and at 6 bar, he would have been exposing his beer to upwards of 88psi. considering that most corny kegs are only rated to 50psi, I felt that truly trying to use 6 bar would end up in quite a bang.

** People tend to be confused on this, and claim it's because of Boyle's law. It's not. It's Henry's law, which is a useful thing to know next time you hear some pompous putz give a lecture on keg carbonation ;)

*** This is not quite accurate. By convention, when we talk about carbonating beer we talk about ADDITIONAL volume. So in fact, when we carbonate something to 2 volumes it actually has THREE times the amount of gas. The original one volume, plus two volumes' worth of carbonation. This is why the chart has measurements below one, because you'd actually end up with just a little more than the volume of gas you already head.

Thursday, May 21, 2015

It's my party and I'll gyle if I want to (part 2)

(Wow.. Two posts in the same year, not to mention the same month... )

OK, so last time we talked about partigyle and the myth of free beer. I discussed how to figure out roughly what you can expect from second-runnings beer and ways you can improve it. I also mentioned (at least, I think I did) that the big problem with this is that it's very hard to plan ahead and brew a second beer of your choosing. While this is not necessarily a huge problem for some people (the "hey, it's beer, I'll drink it" crowed. You know who you are.. ) some of us like to have the beer we LIKE on tap, not just the beer we ended up with...

So, how do you make a deliberate  second-runnings beer? Or possibly a better question: How do you make two beers out of the same mash?

Let's say that you want to make two beers, a porter, and an IPA, and being a complete lush, you want a full keg of each (That'll just about tie you over for the weekend, wouldn't it? Yeah, I thought so...) Full keg is about 18L (we're talking cornys here), so you need about 36L of beer at the end of the process. Call it 40 with losses and trub. How do you make it?

Let's start by taking a look at the two beers that you want to make and look for any commonalities, I deliberately chose two beers that seem very different for this example (cause I don't believe in coddling). So...

For the IPA
OG: 1.065. FG: 1.012 IBU: 64 
85% Two row, 5% Munich, 8.5%, Crystal 15, 2.5% Crystal 40

On my system I get about 72% efficiency, so that means I need about
 4.75kg Two row, 300g Munich, 450g C15, and 100g C40. (For a 20L batch)

For the Porter:
OG: 1.052 FG: 1.013 IBU:27
74% Two row, 10% Brown Malt, 10% Crystal 40, 6% chocolate malt or 
3.4kg Pale, 450g brown, 450g C40, 285g Chocolate.

We'll start with the malt. More precisely, we'll start with the base malt, because the steeping grains don't require mashing and can be, well, steeped. Going through the calculation we've learned in part 1 backwards, we can say that 20*65=1300 + 20*52=1040 == 2340 total point that we are going to need for these beers.

Of that, the percent that comes from the base malt can be calculated per-beer, so for the IPA 85% of 1300 = 1100, and for the Porter 72% of 1040 =750. Together, that means that if we wanted to do a mash of Two Row only, we would need a mash that can provide 1850 points.

Now that we have that number, we can decide how we want to achieve this amount of sugar.  Basically, we have two choices: We can increase the gravity, or we can increase the volume.

Increasing the volume goes like this: We need 20L of 1.055 wort for the IPA, and another 13.5L for the Porter. This is because 1.055 is the relative part of the base malt in the IPA (with another 1.010 coming from the steeping malt.) For the porter, we will dilute the 13.5L with 6.5L of water to achieve 20L of 1.037, which is 72% of 1.052 - the relative part of the base malt there. To double check that figure we can calculate back: 55*33.5=1842.5. Close enough.

Increasing the volume has advantages: A lower wort gravity means better hop utilization, for example. But the biggest disadvantage of this idea is that you have a lot of wort to boil. For a 33.5L final batch size you'd probably have to bring something in the neighborhood of 40-42L to a rolling boil. Most of us who do 20L batches don't necessarily have the capability to boil that much liquid, both in terms of kettle size or heat, and trying to brew that size batch on a system that's dialed in for half of it is just asking to screw things up.
The other option is to increase the gravity: We know we need a total of 1850 points in our kettle. For a regular 20L batch size that makes 1.0925 OG (1850/20), which is the size of a good size DIPA or RIS, but not out of reach for most homebrew systems. Of course, as with high gravity brewing you have to take into account lower efficiency and utilization, but to my mind this is still the better option. Especially if you've brewed "big beer" before and are familiar with how your system functions under those conditions.

So that's those are the basics. So far I've only talked about the base malt, and there're still the questions of the steeping grains and the hops, but this post is already getting long, so I'll talk about those things in part three of this series...

Wednesday, May 13, 2015

It's my party and I'll gyle if I want to (part 1)

(Yeah, I know I have only written one post in the past two years. Been busy...)

So, let's talk about partigyle, second runnings, and the myth of free beer. For anyone who doesn't know, partigyle is the practice of making two (or more) beers out of the same mash by using the second (or more) runnings to brew an additional batch. It is a combination of the two terms "partial" and "gyle", which is an old term for mash runnings. Fuller does it with their London Porter to do their London Pride beer, for example.

The theory is that you can brew a batch of beer, especially a big one where the efficiency tends to drop, and after you've hit your volume and numbers for that batch, you can continue sparging and collect more wort to make a second batch. One mash, two beers, and best yet, since you were going to make the first batch anyway, the second one is kind of a bonus. Free beer!

How does it work? Well, let's say you brewed a big beer, like a 1.080OG Double IPA kinda thing, and you used about 8Kg of grain to do it. Typically, the more grain you mash (above a certain point), your efficiency drops, so whereas on your 1.050 APA you might be getting 75% efficiency, here you'd only get 66%.

Now, for simplicity lets assume you are using strictly 2-Row grist. 2-Row has a potential yield of 37 points per gallon (PPG). This means that, theoretically, if you extracted ALL the sugar from ONE pound of grain, into ONE gallon of water, you will have a gallon of 1.037 wort. From that number you can derive the amount of sugar you can expect in your mash. We'll look at the calculation in metric:

1 kg is 2.2 pounds, so 37*2.2=81.4 Points Per Kilo.

3.74 Liters to the gallon, so 81.4*3.74 =  304.5 Points Per Kilo Per Liter

In our case, we have 8 kilos, so that's 8*304.5  = 2436 total points in our batch

2435 divided by 20L (batch size) = 121.8. Convert to S.g. that's 1.122 wort

Now of course, that's a maximum potential yield. We are expecting an efficiency of 66% so 121.8 * .66 = 80.388. or 20 Liters of 1.0838 wort. We'll take that :)

Now lets look at what's left behind. We had 2436 total points in the grain to extract. We actually extracted 80.38*20= 1607 pf them. That means that we still have 828 points in there. Divided by 20L we get 40.4, or 20L of 1.040 wort. That's plenty good for another beer. Right?

Well... no. Or at least, not quite.
First of all, you don't ever sparge your grain to depletion, the general recommendation is to stop sparging at 1.010 in order to avoid tannin extraction. Second, that's figure of 828 is maximum potential theoretical yield. Your results WILL vary.

So how much can you get? Well.... We said that your typical efficiency on your system was 75%, and in this big batch you got 66%. Let say that because of all the extra sparging your total efficiency (both beers combined) will be 81%. So you get 15% of the original maximum yield. 2435*,15 = 365
or 20L of 1.018 wort. That's a much more reasonable number. In general I think your runnings after you got your first full batch will be between 12 to 18 percent of your initial maximum theoretical yield. YMMV.

1.018 is not exactly a  DIPA strength. In fact, if  you consider that even a Mild, probably the lowest alcohol beer on the BJCP guideline, starts at about 1.030, it's pretty useless. So no free beer for you with those numbers.

 What CAN you do with it? Several options:

  1. Make a half batch - Instead of 20L of 1.018 you can have 10L of 1.036. That'll get you in the range of some English beers or maybe even a blond ale. Remember that you still need to boil, hop, cool, pitch yeast and ferment this though. Not sure everyone would think it's worth the work for 10L
  2. Cap it - Add more grain to the mash and let it mash while you're brewing your first batch. Remember that a kilo of grain will add a theoretical 304 points to your batch. And since these weren't mashed in the first batch, we can calculate about 75% from them, so about 11.5 increase in a 20L batch (304/20*.075). Or in other words: chuck another 2 kilos of grain on top of your mash and you'll get 20L of about 1.041 wort. Respectable, but you need a pretty big mashtun.
  3. Add extract - Same concept as capping, but you don't need the a bigger mashtun, and you have a known quantity because you know exactly how much extract you're adding and what its yield. Extract is generally more expensive than grain though, and sometimes you can run into freshness issues. 
  4. Add specialty grain - Remember in the beginning when I said you're using 8KG of two row? Well who said you have to stay there? A typical "Crystal" or Roast malt will give you about 20PPG when steeped in water (see so steeping about a kilo of specialty grain will give you about an 8.2 point bump in SG for a 20L batch. (20*2.2 = 44 * 3.74 = 164.5/20=8.228) This is not enough to bring your 1.018 wort into respectability, but combined with capping or extract it will allow you to make a completely different beer style. For example, a mild, a brown porter, dry stout, or an American Amber are all fairly small beers with a high percentage of specialty malts. 
My favorite approach is to combine methods 3 and 4 and to try to have a specific goal in mind in terms of the second beer. I can then brew my first, see what kind of extra runnings I get, and adjust accordingly with steeped grain and extract. 

In this part I've walked you through the basic calculation of parti-gyle, and how to approach the recipe development. In part 2 I'll go into two other types of 2-for-1 brewing: Split batch and high gravity brewing. Hopefully, it wont take another year to write... :)