Robobrew drop in efficiency all of a sudden

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Halfakneecap

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I have a robobrew, just doing my 90th batch in right now.

The last 4 or 5 batches ive been a good 8 points short. Preboil samples are much lower than id expect, so i boil the crap out it and still come up 8 points short.

These are all similar beers to what i always brew ( 1.040 ).

I have been using different base malts. One of them being gladfield pils, which seems to like a very open mill gap. I have been playing with mill gap since then, but im pretty much at .040'', which seems to be a pretty good spot for Robo's.

Spent grain does not taste overly sweet, and i have noticed i seem to have more boil volume after the mash. Odd.


I have a new bag of Atlas, so will have consistency to try a few things.


Beers turn out fine, just on the lighter side. Annoying though.


Rant over!
 
The higher boil volume seems to mean less absorbtion from the grain. So you could back calculate the amount of boil volume you received and work out how much you expected, then work out the new absorption rate. I'd say that could be a possible issue for the boil volume difference and some points.

You can try to run your grain twice through. There's also spraying down the grain with a mist to soften the hills before grinding.

Some grains have different diastatic abilities, so it's also possible this is a lower one.
 
The higher boil volume seems to mean less absorbtion from the grain. So you could back calculate the amount of boil volume you received and work out how much you expected, then work out the new absorption rate. I'd say that could be a possible issue for the boil volume difference and some points.

You can try to run your grain twice through. There's also spraying down the grain with a mist to soften the hills before grinding.

Some grains have different diastatic abilities, so it's also possible this is a lower one.
The extra volume i find odd. I always eyeball how much the boil volume is on the graduations in the kettle. Ive recently started writing it all down. But i have been playing around with the crush, so makes sense i suppose.

Running the grain through twice is easy enough, so ill try that. Never had to bother but easy to do.


Its just odd ive had so many batches through the robo with no issues. It does coincide with the gap adjustments.

With a 100 minute hard boil with both elements the whole boil, i ended up 6 points short of predicted OG. 1 or 2 im fine with, but 6 is a bit too much.

Much appreciate the reply
 
Could you post the recipe?
Sounds like crush, condition the grain with 2% by weight of water, leave for about 15 minutes and then crush with the gap a little tighter.
I find that pils doesn't do quite as well as ale malt.
 
Could you post the recipe?
Sounds like crush, condition the grain with 2% by weight of water, leave for about 15 minutes and then crush with the gap a little tighter.
I find that pils doesn't do quite as well as ale malt.
Its been 4 or 5 of the last batches.

Very similar beers, mostly pils ( i always use pils malt as base, for a long time with no issue ), i dont use a lot of spec malts.

Looking over my brewing notes, i had to change the gap for Gladfield pils malt, it apparently likes a fairly open gap. Next batch with Heidelberg pils, quite short of OG, which makes sense with the open gap. I did re close the gap, but its been the same setting for so long it isnt marked, so kind of winged it.


Todays beer was an american wheat, 25% wheat, crushed at .020", then Atlas at .040''. 6 points short, after a hard 100 minute boil. Better than the previous, but not great.

Im thinking crush. I have a new bag of pils malt, so at least that will give me more consistency ( ive used a few different base malts the last few brews )

Bit odd, as ive often used different base malts batch to batch, for quite a while with few issues. I havent changed my mill gap forever, thinking it must be that, i hope.
 
All of this discussion is really just speculation since we are missing the critical measurements needed for diagnosing mash issues. The data that should be collected are:
  • Total grain bill weight
  • Weighted average extract potential for the grain bill
  • Weighted average moisture content of the grain bill (this is the least critical of the data points, but useful)
  • Strike water volume
  • Sparge process
  • Sparge water volume (if batch sparging)
  • Times and temps of all mash rests, including transition times between steps
  • End of mash wort SG, after complete wort homogenization, and prior to adding any sparge water
  • Pre-boil volume and SG
  • Post-boil volume and SG (OG)
With the above data it is possible to separate mash efficiency into its two factors - conversion efficiency and lauter efficiency (mash efficiency = conversion efficiency * lauter efficiency). This allows you to determine if your low efficiency is due to incomplete conversion of starch to sugar, or due to poor lautering process. You need to know which, as the fixes are different for each.

Accurate measurements are critical as the calculated results can be no more accurate than the measurements used in the calculations. i.e. if your volume measurements are +/- 10%, then your calculated efficiency values will be at least +/- 10%, and probably worse.

It was mentioned that different grain sources were used over time. This can mean you have different grain extract potentials, but also different gelatinization behavior. Some grains will gelatinize faster at lower temperatures than others, and this can have a huge effect on the time to reach 100% conversion in the mash, and the coarser the crush, the larger this effect is.

Brew on :mug:
 
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All of this discussion is really just speculation since we are missing the critical measurements needed for diagnosing mash issues. The data that should be collected are:
  • Total grain bill weight
  • Weighted average extract potential for the grain bill
  • Weighted average moisture content of the grain bill (this is the least critical of the data points, but useful)
  • Strike water volume
  • Sparge process
  • Sparge water volume (if batch sparging)
  • Times and temps of all mash rests, including transition times between steps
  • End of mash wort SG, after complete wort homogenization, and prior to adding any sparge water
  • Pre-boil volume and SG
  • Post-boil volume and SG (OG)
With the above data it is possible to separate mash efficiency into its two factors - conversion efficiency and lauter efficiency (mash efficiency = conversion efficiency * lauter efficiency). This allows you to determine if your low efficiency is due to incomplete conversion of starch to sugar, or due to poor lautering process. You need to know which, as the fixes are different for each.

Accurate measurements are critical as the calculated results can be no more accurate than the measurements used in the calculations. i.e. if your volume measurements are +/- 10%, then your calculated efficiency values will be at least +/- 10%, and probably worse.

It was mentioned that different grain sources were used over time. This can mean you have different grain extract potentials, but also different gelatinization behavior. Some grains will gelatinize faster at lower temperatures than others, and this can have a huge effect on the time to reach 100% conversion in the mash, and the coarser the crush, the larger this effect is.

Brew on :mug:

When i studied Quadratic equations and imaginary numbers i thought i was done with such intricate maths!

Im a data nerd, but not that much of a data nerd haha


Basically,

* 85 of the 90 batches ive done in my robobrew ive had no problem hitting predicted OG within 2 points, regardless of brand of malt for same OG and Volume. Very consistent results.

* I played around with my grain mill gap recently, and have had issues since. I have looked over all my other brewing processes, probably too hard, and have probably confused the issue, given the grain mill gap adjustment.

Appreciate your reply, and you are right.
 
When i studied Quadratic equations and imaginary numbers i thought i was done with such intricate maths!

Im a data nerd, but not that much of a data nerd haha


Basically,

* 85 of the 90 batches ive done in my robobrew ive had no problem hitting predicted OG within 2 points, regardless of brand of malt for same OG and Volume. Very consistent results.

* I played around with my grain mill gap recently, and have had issues since. I have looked over all my other brewing processes, probably too hard, and have probably confused the issue, given the grain mill gap adjustment.

Appreciate your reply, and you are right.
It's not such intricate math. There are no quadratic equations, complex numbers, differential equations, etc. required. It's all just arithmetic and algebra.

Brew on :mug:
 
So, my mate has the same robo as me, and the same grain mill, and brews to fill the same size No chill cubes as i do. Up until the above, were pretty much identical efficiency etc.

I checked his mill gap. .032". I adjusted mine to that.

Brewing a bitter this morning. Predicted OG 1.033, my pre boil is 1.035 haha.

Think i found the issue, as suspected by most of you.


Funny, ive been brewing all grain since 2004, and ive never really had to think about mill gap. Both mills ive had ive just used as they came.


Have also added a few more data points to my brew day spreadsheet

*Mill gap*
*Pre Boil Volume*
*Post Boil Volume*
 
Thanks for the update!
10 points over calculated OG haha. Will have to modify efficiency calcs next few batches til its consistent, but otherwise pretty happy its back to normal

Much thanks to all people who responded!
 
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