Sweet Potato Wee Heavy, my first bottle bomb

With Thanksgiving coming up — and of course with my penchant to make complicated beers I am grossly unprepared for — I decided I wanted a sweet potato casserole beer.  I did some reading on adding potatoes to beer and decided I’d bake one so it caramelizes and add it to the boil, then filter it out before it goes in the fermentor.  I love wee heavys, was fascinated by the technique, and thought it’d go well with this idea.  I planned to use a vanilla bean in secondary to impart a little more sweet taste and maybe a hint of marshmallow.


  • 1.5lb Marris otter
  • 6oz 60 crystal
  • 2oz special b
  • 1oz roasted barley
  • 1/4oz East Kent goldings
  • 1/2pkg Windsor Ale yeast
  • 1sm sweet potato
  • yeast nutrient
  • irish moss
  • gelatin finings
  • vanilla bean

For the grain bill I used mostly Maris Otter, a traditional British malt, some crystal 60 for color and sweetness, special b for some carmely raisin flavor, roasted barley for color.  I used some traditionally British EKG hops for an earthy taste that would go well with the potatoes, and Windsor ale yeast, for a fruity low-attenuator.

I mashed in at 154, sparged out the first runnings into one kettle, and lautered in to a separate kettle.  Wee heavy technique has the first runnings cooked down to reduce by half and then added back into the main kettle.  Once it was all boiling together, I added the whipped sweetpotato, the EKG at 60 and 30.  Cooled it, and passed through a strainer and filter several times to aerate and remove the considerable trub.  Pitched at 70, put in the closet.

This was right around the time I was learning that my previous issues with beer were temperature related, so this beer spent about a day at 73, then got the evap skirt.

There was a TON of potato trub in this beer, so I racked it after three days to a new carboy.  After two weeks, I added a vanilla bean.  After about five days, I noticed a slight sheen on the top of the beer.  Wasn’t sure if this was an infection or just oils from the bean or what.

After about five days I bottled. I’d finally got a hydrometer, so I knew the FG was pretty high but I didn’t have an OG to compare it to. Plus, by their nature Wee Heavys finish pretty high.

img_57291Three weeks later I tasted.  This beer was okay, I guess.  It had still picked up some phenols from the start.  It didn’t taste much like sweet potato casserole, or potato at all, or vanilla, but there was something different about it.  Maybe an advanced palate could pick out the potato, but I wouldn’t have been able to name that as what was unique.

Another week or so went by.  I ended up going out of town for Thanksgiving.  I’d originally envisioned bringing this beer to wherever I celebrated the holiday and sharing it with people.  However, I was traveling to a nearly alcohol-free home where no one would be drinking, and I wasn’t proud enough of the beer img_57471to leave it behind for my family to have during their gathering.

When I returned I chilled down a beer, and noticed that one of them had leaked.  I’d been using Alaskan bottles because I  liked their stubby size, but noticed that it felt like their mouth was just slightly larger than taller bottles and it didn’t quite feel like the caps went on as snug.  When I opened the beer, it was my first gusher.  Beer foamed out and I had to sit it in the sink for a while.  When I finally poured, the head was huge.img_57571

There were a few explanations here:

  1. Sweet potato.  This should be a fairly simple starch and sacc should ferment it, but it’s new territory for me.  Perhaps it takes much longer to ferment and I bottled too early, leaving too much fermentable potato in the wort.
  2. Windsor yeast.  Many people report low attenuation from this yeast.  That’s a common complaint with yeasts that will taper off pretty sharp; there’s sometimes a risk that the yeast is still working, though slowly, so you end up bottling a beer with too much residual sugar in it and yeast that aren’t done working through it.
  3. An infection.  Remember that film on top?  Maybe I caught some sort of bug, and while the Windsor had given up on attenuation, the bug was still working through the wort.

I should’ve seen what was coming.  I drank through most of the just-okay-and-sorta-gushery beers, saving a bomber like I do with every batch to have months down the road.

On December 21, about six weeks since the beers were bottled, my wife sent me a text:

Wife: “Something exploded.”

Go figure.  At this point in time I’m going with the theory that all three factors above led to this conclusion.  I put a low attenuating yeast into a difficult-to-attenuate beer that had a non-typical fermentable in it, then introduced a vanilla bean without proper sanitation, which brought some sort of outside contaminant in it.  The Windsor gave up and I decided it was time to bottle, putting a bug and a bunch of not-finished beer into bottles.  A month and a half later, the resultant carbonation caused my closet to have a sticky, glass filled mess.

At least I learned this lesson with just one residual bomber and had only made one gallon of just-okay beer.


4 thoughts on “Sweet Potato Wee Heavy, my first bottle bomb

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