Nice post Bill
. Just caught it before posting the below...
[Managed to make that phone call re the lagering. The many time, gold medal lager brewer I called who also has micro-brewing experience first comment was, "Well, lagering in the fermentor would be fine but who can afford to tie up a fermentor???" Talked on it more and we can't see any major rights or wrongs on this but I wouldn't mind some more info. Probably worth another thread on that topic, "Lagering - before or after priming?"]
2trout, I'm hoping that the following will ease your mind a bit and make answering the temperature question much easier. You've been on this site long enough to know that we like coming up with simple, well thought-out solutions not simplistic answers.
You also know that there are many basic areas that there are still no answers to in brewing and that the only remedy then is to at least be informed. I'm going to really concentrate on this answer so let's see if we get lucky here on getting an answer, getting informed or me just getting drunk
The Temperature Question - Understanding the Science
I think there are two things that we need to understand here which then make everything else a lot easier.
The first thing we need to do is understand that cold wort can hold more CO2 in solution than warm wort.
The second thing to understand is that CO2 must be getting actively
put into the beer. In other words, if there is no fermentation activity going on you will not be able to increase the CO2 levels.
Three Different Scenarios
Let's look at three different scenarios...
1. An ale (or lager) fermented at a constant temperature e.g. 18 C - Input 18C as that is the temperature that the wort has been at while consistently exposed to an active CO2 input (fermentation).
2. Lager fermented at a constant 9 C and then given a diacetyl rest at 14C and then bottled - Input temp would be 9 C. Why? Well, if you are doing your diacetyl rest correctly (btw please note that a diacetyl can be avoided by using other practices) then you will be gradually lowering the temp back to 9 C and there will be definite active input of CO2. (Ah!, I remember now, that
is the reason I over-wrote a very old 'BIABacus' priming formula a member wrote some time ago that gave the diacetyl temperature priority. In other words, existing formula is fine.)
3. Lager fermented at a constant 9 C and then given a diacetyl rest at 14C and then lagered at 1C for say, two months before bottling. If you do use this method, from what I have read today, it is important that you get down to lagering temperatures while there is still about a third of fermentation left to go. If you leave it too late then Noonan says you must reduce your lagering time. (Not sure why and there are many other 'rules' in Noonan's book that give no reasoning.) My guess here is that Noonan is saying that lagering should be done whilst there is still fermentation activity going on. The lowering of temperature is simply slowing this last bit fo ther ferment right down. Interesting. But, what is the temperature answer?
One and two above are easy. What about three?
In my first post in this thread I mentioned time and that is where we are back to now. As an extreme example, if you left a beer for a year in a fermentor at 1 C (or 18C), at the end of that year, it will basically have no CO2 in it. Same as if you left a bottle of Coke in the fridge (or outside) for a year with the lid off. In other words, you might as well put in 37 C as your temperature as that is the temperature at which the maximum amount of priming sugar is required. (The scenario I am using says you'll need 3.2 grams per 500ml bottle).
At the other end of the time scale though, if you have carefully measured and timed all the lagering procedures outlined by Noonan, it probably works out that you reach final gravity just as the lagering process ends. Great! Then just use 1 C as your temperature as the wort will have had an active CO2 input at that temperature. (The scenario I am using says you'll need 1.5 grams per 500ml bottle).
As a matter of interest in this same scenario, if we put in 9 C we end up with 2.2 grams being required per 500 ml bottle.
Do we have an answer yet?
I think we certainly have answers on scenarios one and two and even scenario three but, but, but,...!!!
What about in 2 trout's case where he has had the beer sitting at about 4 C for 45 days?
Well, that temp is too high for lagering for that long (unless you want to read pages and pages of Noonan's stuff, trust me on this
). So I think that at 45 days at that temp, the beer will not have much CO2 in it at all. Your judgement on this though will be as good as mine. And that's where we are at on this - judgment.
All we know so far on 2trout's wort is that he probably shouldn't be using only 1.5 grams of sugar per 500 ml bottle to get 2.5 vols of CO2 but he also maybe should not be using 3.2 grams per bottle.
The Worst Case Scenarios
As a matter of interest and to put things into perspective, let's pretend that 2trout was
lagering at 1C not 4C. If 2trout only uses 1.5 grams per 500ml bottle and his wort had no CO2 in it, he would end up with a beer with about 1.5 vols of CO2. A bit flat for sure.
If 2trout uses 3.2 grams per 500ml bottle and his wort actually was full of CO2 at 1 C, he would end up with a beer with about 3.5 vols of CO2. A bit too lively but he's not going to kill himself
If he puts in 2.2 grams (the value required at 9C) he'll end up with somewhere between 2.0 and 2.9 vols of CO2.
you are not sure, then go for the primary fermentation temperature.
My Personal View
The priming formula we are using in the BIABacus is the most advanced available. This does not mean it should be treated as a god though. Very few brewing formulas are
god-like and this is the point that mally was making above and that I also like rambling on about...
Use numbers to get you into the ball-park. (The BIABacus numbers are the best you'll get as they are very carefully written and studied, so do use them). But, what if they don't work?
Well, the whole aim of the BIABacus and this site is to get brewers asking the right questions. For example, if we had scenario 1 here on the priming and the beer tasted over or under-carbonated then there is a process that we can work through. The first part of that process is for the brewer to be willing to distrust their own measurements. The second part is for the brewer to be willing to repeat what they think
they did on the next brew/s. The third part is to then be prepared to adjust the formulas - knowingly.
Slow and steady wins the race on this stuff.