I've just put the extract version of this in the fermenter: http://www.wagonbrewing.co.nz/panhead-port-road-clone?search=pilsner

The gravity is 1.037 which seems way low. Dammit I don't want no weak beer! But I don't understand why it is so low. I did a partial boil (13L once the extract was added), chilled, siphoned to the fermenter and then topped up to 23L per the recipe. Wishing now I stopped at 20L and took a reading. Also aerated it by shaking the fermenter so it is definitely not a mixing issue messing with the reading. There is maybe 1cm of fluid/hops gunk left in the kettle. What happened?

One thing that was not great was the stove I was using was underpowered so it was a weak boil.


  • 2 x Black Rock Ultra Light Extract 1.7kg Can
  • 250g - Weyermann Carahell Malt (Steep)
  • What extracts you used, and how much of them?
    – Mołot
    Apr 30, 2016 at 17:53
  • I doubt a weak boil would alter your OG post-topoff. Do you know what the OG was supposed to be? 1.037 is on the lower end for a recipe, but not that uncommon.
    – Vince
    Apr 30, 2016 at 20:37
  • Deleted my answer because I couldn't re-create my results. Probably I entered extract parameters wrong, because second time I got 1.046. My bad. By the way - were you stirring during boil?
    – Mołot
    May 1, 2016 at 22:39
  • No worries. No I didn't stir very much during the boil. May 1, 2016 at 22:41

3 Answers 3


You say your boil was weak, and you didn't stir much. Extracts are hard to dissolve properly. Even vigorous boil without stirring may fail to do it. And 10-20 minutes of vigorous stir before wort boils may be barely enough. And it gets worse the less water you have in boil, so partial boil brews are most exposed to this risk. Sugars are heavier than water, so if not dissolved enough, they concentrate on the bottom.

What I guess happened is that a lot of sugars stayed at the bottom, with your hop waste. You would lose some of theoretical 1.046 anyway, but you probably lost more than you needed. Your results are consistent with loss of 0.4kg of liquid extract. Within what I can imagine in 1cm of gunk liquid. Especially given the fact that most extracts are already boiled, so you shouldn't have hot break - you shouldn't have any waste except spent hops, but it looks like you think you did.


If you have some dry malt extract (or liquid), you can get the gravity to where you want it now. It's not too late to add the DME, even though it's already in the fermenter.

About 1 pound of DME should get you up to about 1.045, which should give you a roughly 5% abv beer.

  • Thanks Jeff I'll try that. I think I'll add 50/50 DME and Dextrose, or even all Dextrose since I want to go for dryness, and I'm kind of digging the flavour and colour right now! Do you think I should pitch some additional yeast in with the malt addition to make sure it attenuates more fully? May 1, 2016 at 21:16
  • 1
    I'm not quite clear about what stage your beer is at, but no more yeast should be required.
    – Jeff Roe
    May 2, 2016 at 3:58
  • Thanks. It's been in the fermenter for about 36 hours, the airlock bubbling peaked maybe 18 hours ago and is now beginning to slow, once every 5 seconds now. May 2, 2016 at 4:14
  • I don't think I've ever added a big hit of fermentables at that stage, but the yeast is very active and you shouldn't need to add any more yeast.
    – Jeff Roe
    May 2, 2016 at 4:33
  • So your suggestion worked great with the addition of Dex/Malt mix to the primary to bring up the gravity. I'll add some details in a separate answer as they might be helpful to others trying this procedure for the first time. The behaviour of the yeast after the addition was very interesting. May 25, 2016 at 0:20

To fix the low gravity I followed Jeff's suggestion and added dry Dextrose/Malt mix. Here's the details in case someone else wants to try this procedure for the first time.

I did some calculations in BeerSmith and added 1kg of Dextrose/Malt mix into 1.5L of wort from the fermenter + 1.5L of boiled water. Boiled this then cooled to fermenter temp (24C). This was added 3 days after racking to primary and added 1.017 to the gravity in the fermenter to give me an equivalent OG of 1.054.

The way the yeast responded to the addition was fascinating with the fermentation rate increasing briefly, then almost stopping completely before resuming rigorously all in the space of an hour:

  Time   |   Stage            |    SG   |  Airlock Bubble Interval   
 0       | Racking to Primary |  1.037  |  0
+36h     | Primary            |  1.017  |  5 seconds
+72h     | Before DME/Dex Add |  1.015  |  23 seconds
+72h 15m | After DME/Dex Add  |  1.032  |  18 seconds
+72h 20m |        "           |    -    |  Almost stopped completely
+73h     |        "           |    -    |  10 seconds
+73h 30m |        "           |    -    |  3 seconds
+8 days  | Primary            |  1.019  |  68 seconds
+10 days | Primary            |  1.016  |  0 (possible slow leak)
+12 days | Fejoa + Dry Hop    |    -    |  0
+13 days | Primary            |  1.013  |  0
+18 days | Final              |  1.013  |  0

It didn't quite attenuate as much as I'd hoped but on bottling the beer smelled and tasted great so I think it has all worked out.

  • 1
    Cool. I think I can explain the "Almost stopped completely". I think the mixing I'm assuming you did when you added the DME/Dex knocked some of the CO2 out of suspension in the beer. The yeast continued to produce CO2, but instead of coming out of the airlock it was just re-saturating the beer. Once the beer was re-saturated with CO2, it started coming out of the airlock again.
    – Jeff Roe
    May 25, 2016 at 1:00
  • Ahh that's a great thought, although I actually didn't mix it I just poured it in slowly thinking diffusion would be sufficient. But still there was a tiny bit of disturbance. But would your idea explain why fermentation increased immediately after the addition and then dropped right down before recovering? May 25, 2016 at 3:07

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