Mystery Brewing Responds To Growler Explosions

From Mystery Brewing:

We’ve recently heard a couple of stories coming out of the market of some of our growlers exploding, and we’d like to talk about it a little. In fact, we’d like to say:

That’s terrifying and unacceptable. If you’ve had a growler explode, we’d like to hear about it.

To give you a little bit of an idea of what’s going on, we thought we’d talk a little bit about our beer and growlers:

Growlers should be kept cold all the time

In the grand scheme of things, this is true for all beer, but it’s especially true for ours. Our beer is unfiltered and unpasteurized. We do it on purpose because it makes beer taste better. It also means that there is at least a small amount of yeast in all of our beer, sometimes a lot, depending on the style. When our packages are moved around, that yeast starts getting kicked up into the beer and can easily start fermenting again, if the growler is in a warm environment. Cold environments cause yeast to go dormant, but once it’s warm it can get back into solution, start eating a little bit more sugar and release more CO2, creating more pressure inside the growler than we had intended.

And warm? It isn’t that warm. You might think your kitchen is pretty chilly, but yeast loves hanging out around 62F – 65F and can even be active in the 50F range.

On top of that – growlers are by and large re-used containers. They’re not flawless. While a good portion of the growlers that we release are new growlers, 40% – 50% have been returned to us from stores, rinsed, cleaned, sanitized, and re-filled. In that process, during shipping, getting loaded in and out of trucks, and moving around the brewery, growlers get banged around a lot. When they clank against each other in the store or in boxes, it can create tiny microfractures in the glass that, under normal pressure, we probably won’t notice before the growler hits a recycling bin somewhere. Under an elevated pressure, however, those microfractures could easily crack and split. We inspect each growler that we use – we look for chips, cracks, and bubbles in the glass and if we see anything that looks like it’s potentially unsafe, we throw that growler away. But we can’t catch things we can’t see, and our growlers should never see the type of pressure that would make one explode.

Plain and simple, growlers should be kept refrigerated at all times.

However, we’ve done a terrible job at letting you know that. We had a breakdown of communication with our distributor that meant that not only were our growlers being stored warm in the warehouse, but they were being delivered to stores where they were also kept warm, which created – for a limited number of brands in a limited number of locations – a very dangerous situation.

That’s our fault.

Going forward, we’ll be including labels on all of our growler boxes that note that growlers should be stored in refrigeration, and on our next and all future rounds of printed tags, we’ll be including the warning: “This product is unfiltered and unpasteurized. Please refrigerate.”

Our growlers are safe

The vast majority of our growlers on the market are fine. The brand we know of that was stored warm was the last batch of St. Stephen’s Green and as far as we know it has all been removed from the market. However, we are unsure of where or when our growlers have been stored warm in a retail location.

If you ever see any of our growlers stored warm please tell us! It’s not good for the beer and it’s not good for the store, and we’d like to make sure that we communicate with that location to make sure we’re all happy and enjoying great beer.

Finally, if you’ve had a growler explode, we’d like to make it up to you. Please, let us replace your growler, refund you for the growler that exploded, and treat you to a pint at our pub.

Send an e-mail to growlerswtf@mysterybrewing.com to tell us about your explosions and we’ll do what we can to make it right.

Yours in beer,
Erik Lars Myers
.