[Visor]

   I was perusing my brewing notes today and discovered something interesting, I've used WLP007 for only two batches of beer, and both those beers eventually became volcano beers, as in pop the cap and the beer immediately gushes out of the bottle until less than half the bottle remains. These are also the only 2 batches that I've had this happen to, I've had more than a few over carbonated batches but no Vesuvius Specials.
   Just thought I'd throw that out there.

[GS]

Couple of thoughts...

Is it overcarbonation, or infection?

What are you priming with? Are you measuring it, like say 3/4 cup, or are you weighing it, for instance 3.6 oz.

Also...if you are using a priming calculator, are you accurately capturing the volume being packaged, and the temperature of the beer?

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[Visor]

  My first thought on both was infection, in fact that was my assumption until I realized that the only times it's happened were the only times I used this yeast. I always prime with reserved, boiled and sealed wort from the same batch. I prime using a formula the does take into account volume of total batch including prime and degrees of attenuation or the batch. I have come to the conclusion that the particular formula I've been using over carbonates a bit too much for bottling, but again, not to the point of eruption.

[GS]

Well, there it is. Use a different formula. But I don't see why this particular challenge is yeast-specific.

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[Todd H.]

This happened to me with my last two batches using wlp002.  They were both repitches.  I tossed the yeast after the last batch, assuming it was infected.
I found that it had fermented a further couple of gravity points in the bottle (yes, degassed it first).  Amazingly the caps all held and no bottles burst.
Did you check your gravity after the eruptions?

[salcedo]

Looking at the web page for this yeast, it says the yeast is "highly attenuative" http://www.whitelabs.com/yeast-bank/wlp007-dry-english-ale-yeast. I guess your results confirm that :-)

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[reverseapachemaster]

English yeast can be lazy yeast, especially when fermented on the cooler side. It is possible that the combination of rousing and a little oxidation during bottling convinced the yeast to keep fermenting in the bottle. It doesn't take too much additional fermentation in the bottle to create geysers.

[Visor]

   Well, to add another twist, one of the 2 beers was fine until 3 months after bottling. I remember reading a story in Tony Magee's book about a similar problem they had at Lagunitas once. As I recall, it turned out that some less than ideal lab practices had allowed some extraneous organisms into their yeast culture, and that under just exactly the wrong conditions, with just the right population density this organism, would, after a certain amount of time, begin to further ferment the remaining sugars.
    Looking through my records, the yeast for both batches was purchased at the same time, so it probably was all from the same production lot, so it's not impossible that defective or compromised yeast was the culprit. Not to suggest that is the most likely answer, but it's worth considering. And yes I did hydrometer test the Porter and the final gravity was down by a single point, that is within what I'd consider the margin of error.