First AG brew, missed pre-boil gravity by 24 points

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muppix

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This has been a ’learning curve’ kind of day! Mashing went well (far as I can tell) as did sparging, but I checked the numbers while heating to boil temperature and it looks like I’m 3.5 litres low at 28, and 24 points low at 1.020. OK, the wort was at 65C and not 20, but 24 points?!

I had thought to maybe add some LME and do a post-mortem afterwards, but would prefer to keep the ingredients as-is and maybe just boil a bit longer?

Any ideas? It’s an American Pale 18A via the Brewfather app, using Brewtools B40Pro (and a terminal lack of experience)

🤭
 
Thanks for that! No, I knew that my hydrometer is calibrated for 20 degrees but I didn’t think there would be 24 points difference between 20 degrees and 65 degrees. That calculator give me an updated pre-boil gravity of 1.036, which is better but still short.
 
I just brewed today and took my OG at a higher temp(mid 60's) it was 21 points out. When I cooled my wort sample as I usually due it went from 1.020 to 1.041 so yes it is possible. I usually take a sample jar and cool it in the fridge which does not take that long to get to 20c before taking a reading. Just as a further I also took a refractometer reading at the higher temp too and it was showing 1.042
I would not do anything until your wort sample is at 20c and see where the land lies then
 
Thanks for the help guys, really appreciate it. I can live with the adjusted values and will learn from this experience. Boil is now underway and the 60 minute additions are done.
 
Let us know how you get on and update us on your post-boil gravity/OG.

But don’t sweat it - everyone’s efficiency is poor when starting AG brewing (mine was atrocious!) as we’re learning our equipment and processes. It will get better as you get more brews under your belt. 👍
 
Will do, thanks again. Maybe Brewfather should come with an adjusted efficiency for n00bs like me...
 
Let us know your OG when you take a temperature correct reading I bet you are not miles away
 
Well, that turned into a bit of an epic day yesterday. Started out at 12:50 by measuring out the water and weighing the ingredients, got everything cleaned up again by 21:20. I've learned a number of valuable lessons, including the fact that kettle and brew fridge shouldn't share the same extension lead. Don't ask ...

And of course the 3.5L of sparge water will make a difference to your OG as well.

To be honest I'm not entirely sure how to deal with the discrepancy that is my counterflow chiller. Yesterday I started with the chiller more or less empty and filled my kettle with the requisite amount of strike water - 22.57 litres, and the sparge water heater with the right amount of sparge water - 11.79 litres. OK, in both cases I might have been a little bit off due to using a combination of 5 litre and 1 litre bottles as measuring devices, but I'm sure I was in the right region.

The chiller stayed empty until a couple of minutes before end of boil (was meant to be 15 but I forgot, so more like 5) and I didn't drain it at the end which means I have that loss to add to other losses like boil-off, etc. Going forward, should I measure and add the chiller capacity to my strike water volume in order to get closer to the numbers? That feels wrong because I'd still be diluting the fermentables, so maybe there's a setting in Brewfather somewhere. Need to explore more anyway - had a quick gander last night and found the same SG / temperature calculator that was patiently pointed out to me in an earlier message.

Let us know your OG when you take a temperature correct reading I bet you are not miles away

Funny you should say that, but after chilling to 20 ℃ (and before pitching yeast) I was at 1.050, which is 3 points above the post-boil / OG target of 1.047. I'm a bit puzzled by this. Had my pre-boil been on target (instead of 6 points low) would I have had an ever higher post-boil?

Did you stir the mash? I often get a low efficiency if (most of the time) I forget to stir the mash.

I have to admit this area is one where my lack of knowledge makes me uncomfortable. Nowhere did it say to stir the mash other than at dough-in, and I only did that after the 20 minute rest period which Brewtools recommend in several places, even though their wording doesn't make it 100% clear whether that's the first 20 minutes of your mash time or if it's 20 minutes followed by your mash time. I went for the former, and resisted the urge to give it a stir at the start, despite some grain being above the water for that whole time - I suspect that's a potential cause of low pre-boil SG.

Anyway, back to stirring. During the first 20 minute rest I circulated outside the malt pipe, and after my first stir I blended in the centre pipe in order to drive water through the mash and bring the temperature closer to the water temperature - I think the mash was around 63 and the water at 65 until that point. (penny just dropped: this is why the default strike water target temperature is 68 when you turn the B40pro on)

I wanted to have quite a bit of water through the centre pipe so that any solids that fell through the screen at the base would be sucked back into the mash and not make it to boil, but I found that the more I circulated through the mash the lower the water level became outside the malt pipe, until at one point the dip tube was sucking in air. Good job I had it set high enough to avoid scorching the elements. I adjusted the balance between circulating around / through, and found that stirring the mash caused the level outside the malt pipe to raise again quite quickly, especially if I stirred low down. Trouble is, I'm not sure if I should have been stirring constantly, every 20 minutes, or not at all, so I kept it to a minimum and only stirred when I thought the water level outside the malt pipe was getting too low, because I didn't want to compact the mash too much and ask for trouble when sparging. In the end I think that translated to some stirring every 10 minutes or so.

Phew - long post. In summary I think I need to:
  • Measure water accurately and account for losses in chiller, plumbing, etc.
  • Improve my mash technique; maintain 65 ℃ inside the mash, better understand when to rest and when to stir.
  • Get a better sense of timing. I think I rushed from mashing to sparging (via a brief attempt at vorlauf) and then from sparging to boil because I was convinced bad things would happen if the temperature dropped too much or if the grain bed got too dry.
Once again thanks to everyone who helped out, I appreciate it very much. Here's how the actuals stack up against the recipe:

1616317829064.png
 
I take the preboil gravity at post mash temperature and convert, then leave it to cool and see what it is afterwards as well.

As for volumes, I am always out by up to a litre or so but always manage within a couple of points of OG.

You also need to account for grain and hop absorption, but Brewfather does that for you anyway. I noticed that it has an equipment profile for the B40, so dead space and chiller loss should be accounted for.

My latest brew day I crushed some of the grain too finely, and got a really high mash efficiency, but a really slow sparge.

And my boil off always seems to be less than expected 🤔
 
You also need to account for grain and hop absorption, but Brewfather does that for you anyway. I noticed that it has an equipment profile for the B40, so dead space and chiller loss should be accounted for.

It does have that profile, but IIRC there was only an option for with / without steam hat and condenser (both optional) since they have an impact on boil-off. I don't recall seeing any mention of the counterflow chiller, also optional.

My latest brew day I crushed some of the grain too finely, and got a really high mash efficiency, but a really slow sparge.

Hmmm, that kind of makes sense. I get my grain ready crushed since I don't have a mill yet, and invariably some of the 'flour' settles on the bottom of the bag during shipping. I did my best to mix it all up, though I guess the same could hold true if I were to mill it myself.

Just out of interest, how slow is slow when referring to a 'slow sparge'? I was thinking about this a lot while rehearsing brew day, because I see times online quoted as 60 - 90 minutes and I couldn't imagine why it would take that long. Yesterday I started fly sparging at 16:13 and maintained about an inch of water over the grain bed until 11 litres later I was done ... at 16:19. Three minutes. Even looking back over my notes now I can't believe it was that quick.
 
Usually the sparge takes me about 20 minutes. A 6 minute sparge may account for some of the loss of efficiency. The last slower sparge took about 40 minutes. It needs to be slow enough that it takes as much sugar with it as possible.
 
It does have that profile, but IIRC there was only an option for with / without steam hat and condenser (both optional) since they have an impact on boil-off. I don't recall seeing any mention of the counterflow chiller, also optional.



Hmmm, that kind of makes sense. I get my grain ready crushed since I don't have a mill yet, and invariably some of the 'flour' settles on the bottom of the bag during shipping. I did my best to mix it all up, though I guess the same could hold true if I were to mill it myself.

Just out of interest, how slow is slow when referring to a 'slow sparge'? I was thinking about this a lot while rehearsing brew day, because I see times online quoted as 60 - 90 minutes and I couldn't imagine why it would take that long. Yesterday I started fly sparging at 16:13 and maintained about an inch of water over the grain bed until 11 litres later I was done ... at 16:19. Three minutes. Even looking back over my notes now I can't believe it was that quick.

3 minutes does seem pretty quick! But you've done right maintaining the inch above the grain bed, thats spot on. I usually vorlauf first (4-5L) then get into sparging.

Next time aim to decrease the rate the wort is exiting your mash tun. Slow it all down, and maintain that inch above your grain bed still when you're adding your sparge water. Generally, an optimal sparge is approx. 40 min, and if you slow it down you will take more sugars into your boil. That should sort you a better efficiency too!
 
I was at 1.050, which is 3 points above the post-boil / OG target of 1.047. I'm a bit puzzled by this. Had my pre-boil been on target (instead of 6 points low) would I have had an ever higher post-boil?

Just to answer this particular point: Quite possibly.

But there is something wonky here. If your pre-boil gravity was 1.036 at 28.5L then, by my calculations, you’d have to boil off a rather excessive 8L of wort to concentrate it to 1.050, which would leave you with 20.5L (not taking into account trub/chiller loss).

As I said before though, try not to sweat it too much in your early AG adventures. It can be really hard to work out exactly where your system losses are occurring and will likely take you a few brews to get a better handle on this and getting your equipment profile on Brewfather working how you’d like. I still struggle with where my losses are occurring, years into my brewing journey!
 
Gotcha, thanks. Oddly enough I am down to exactly 20.5 litres, bubbling away nicely now in the Fermzilla, but that includes chiller loss.
 

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