Update: Carbo-Woes; I take it all back...

Some of you may know quite well the fact that I have long been preaching the virtues of repitching with dry yeast at bottling time when batches have been in secondary for longer than 6 weeks. This line of thinking was a result of a wheat doppelbock that I brewed last September. It never carbonated, and had been aging for awhile in secondary. I've always assumed all the yeast flocculated and there wasn't enough in the bottle to carbonate with. So, ever since then, I've been preaching and practicing the "6-weeks+, repitch" golden rule.

Now, I take it all back.

You may also remember a hefe and a wit that I brewed a couple months back that are both vastly undercarb'd. Well, on those batches, I was pretty certain it was the DME being very unfermentable (effing laaglander!), so I ordered a bunch of Munton's carb tabs so that I could pop open the bottles and recarb them.

Well, turns out that the bottles, while undercarbonated, are getting a little better. Unfortunately, some of them gush when opened warm, and if I try to put carb tabs in there...well...I'm sure you all have seen the Mentos & Pepsi videos. Even when cold, and I let them vent their co2, they still gush like a madman when I drop the tabs in.

So, I'm just going to deal with a slightly undercarbonated couple of batches and learn my lesson. But I also decided to pop open the remaining bottles of the wheat doppelbock (which is, unlike the other two batches, almost completely flat). I opened a few bottles last week, let them get rid of any carbonation, and drop a few carbtabs in before (quickly - they like to gush once you put those tabs in there!) recapping. I tried a bottle on Saturday. 100% beautiful carbonation!

So, in this light, I'd like to retract my theory on repitching at bottling (with the exception of lagers, until I'm proven wrong on that front too). That stuff has been sitting in bottles since the middle of last september---just about 10 months---and the yeast in the bottle was still viable enough to turn those carbtabs into alcohol and carbonation.

The moral of the story: don't use extract to carb with, if possible, and if you have to, don't use laaglander. In fact, avoid laaglander altogether. You may as well be using maltodextrin or lactose.

Now...one last question for anyone who might know: going back to my wit & hefe, when I chill them down and open them to drink, they're carbonated, like I said, just not as much as I'd like them to be. But when I open any of them if they're warm, it sits there for about 5 seconds not doing anything...then the bubbles start rolling to the top and roiling the trub...then it gushes if I don't recap it. What's going on here?

One odd thing I have noticed with my Hefe's in particular, is that in the first place they get primed big...usually shooting for over 3.5 volumes. Well in the first week (one week ferment, 2 weeks in bottle...tried after 3 week mark) they were like open and they'd fizz up and flow out of the bottle. Second week after that, the effect goes down and I am guessing in another week it'll be under control. I reason this because the exact same thing happened with my DunkelWeizen. I am not exactly sure why it is so in the beginning and why it seems to settle out later.

As for long term carbonation, one batch I did that was in secondary forever, I carbed it really cool (~60 and much below that probably closer to ~50) with an Ale yeast. It took forever and a day to fully finish out in the bottle, but it is exactly what I had been shooting for, only 6 months late .

as CO2 comes out of solution at the warmer temp, its causing a chain reaction. as each bubble of CO2 rises, it bumps other beer molecules and causes that CO2 to possible come out of solution too.
its like a fission reaction really.

I have the same type of problem.
I made three beers on yeast I got from bottles of La Fin Du Monde. I did one after another on the same yeast cake. They all fermented very well, but after 2 1/2 months or more none of these beers carbed in the bottles. These are the only beers I've done that have not carbed.
Any ideas what went wrong

46 batches and the 3 with the same yeast to forget the priming sugar seems unlikely.