BIAB with a Keggle - 3rd batch and still LOW efficiency

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m3B.eer

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Hi homebrew community!

In an attempt to find out what I could do better, I'd like to describe my brewing processes I just did yesterday, that resulted in me in an appearing 55% brewing efficiency of my batch yesterday. I'm quite frustrated obviously. If anyone experienced with that system may be able to point out to me what may be an obvious miss way, please let me know! I think it has do some with either the volume of strike water of the sparging process.

I recently got my hands on an electric keggle, so I've been doing 10Gal batches instead of my regular 5gals in pots.

Grain bill : 22.2lbs - 20lbs of Pilsen, 2lbs of flaked barley, 0.2 acidulated malt.
Strike water : added 30L, heated it up to 71C. I added a tsp of magnesium sulphate and salt.
Put in my new grain bag fitting the keggle.
Put all my grains in.
I was able to maintain throughout the hour a mash temp around 64-65C.

I prepared 15L of sparge, my goal was to fly sparge, heated at 77C.

Once mash time was over, I hoisted the bag thanks to a pulley system I was just able to set up. It did require me to tie the bag at its mouth, and attach it to the hook on the pulley. I lifted the bag just high enough that it could slightly rest on a strainer I put at the opening of the keggle.
So if you have it : the bag is suspended, tied and attached from its top to the pulley system, but slightly resting on the top of a strainer.

From there, I fly-sparged, slowly pouring the heated water over the bag. This is where it might get tricky, because the bag is closed, but I'm hoping it will let through enough water. I do so slowly, a bit at a time, with a measuring cup, trying to target all the sides of the grain bag. All this while I cranked up the heat to start the boil. It takes me maybe 15-20min to do my sparge.

Then I add my hops according to my schedule, but I'd guess from there, the deed is done. Boiled down for 60min.

I do not take gravity reading preboil. I only took one post boil and slightly cooled down : 1.042.
On the recipe I was looking at, it was saying OG = 1.063.

Other thing : I'm not able to accurately measure volumes (besides what I add in) : My keggle has no markings, nor do my fermenters (6gal pails). So I don't exactly know how much is left and I loose in the trub post-boil, how much I am able to transfer to the fermentors and ferment. It's mostly eyeballed to that point, but I sort of calculate my first runnings and sparge based on what I wish to finish off (10Gal of fermentable wort).

I hope this makes sense, I may be able to illustrate this with pictures if need be.

Cheers!
 
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m3B.eer

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EDIT : I got my grains from where I usually get them, and receive them milled. I thought the mash consistency (in the grain when stirring) was fairly good, not too thick. I supposed the amount of water was not insufficient.
At my first attempt, I tried a no-sparge method, filling more water in the keggle, with a grain bill of 20lbs. Still had a low efficiency but slightly better Og 1.046.
My second batch I had a friend to help me fly-sparge the same way I just explained. OG was better 1.05ish. But being 2, I didn't have the pulley system, so 1 was holding the bag, while the other was fly-sparging and pressing the bag.
 
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doug293cz

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With 22.2 lb of grain and ~12 gal (45 L) total brewing water, your pre-boil SG should have been between 1.059 and 1.067, depending on how effective your sparge was, IF you had gotten 100% conversion efficiency (converted all of the available starch to sugar & dextrins.) The fact that your OG was significantly lower than that indicates that your conversion efficiency was nowhere near 100% (which is achievable.) Assuming your post-boil SG (i.e. OG) was actually 1.045 (SWAG at correcting for warm reading) your conversion efficiency is on the order of 65%, which is terrible.

The most common cause of low conversion efficiency is too coarse a crush to convert in the allotted mash time. You can try to compensate for coarse crush by mashing longer, but the best solution is to get your own grain mill so you can control your crush. With BIAB, you don't have to worry about stuck lauters, so you can crush very fine (0.025" or finer.)

You can determine your conversion efficiency if you accurately measure your grain bill weight, your strike water volume, and the SG of the wort in your mash (after aggressively stirring, or recirculating to homogenize.) The calculation details are given here.

Brew on :mug:
 
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m3B.eer

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Thank you for your detailed answer Doug. So you think it doesn't have to do with my sparging method.

I'm not sure when I can get a mill, but if by next brew I can't, I'll ask my supplier to double or grain thinner, and explain to him the situation.

I preboil gravity ready has to be adjusted for temperature but should be quite accurate the define the forthcoming OG?
 

doug293cz

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Thank you for your detailed answer Doug. So you think it doesn't have to do with my sparging method.​
I'm not sure when I can get a mill, but if by next brew I can't, I'll ask my supplier to double or grain thinner, and explain to him the situation.​
I preboil gravity ready has to be adjusted for temperature but should be quite accurate the define the forthcoming OG?​

I doubt your sparge process had much to do with the extremely low OG. The range of pre-boil SGs I gave included no-sparge at the low end.

To completely diagnose mash efficiency problems, you need to take the following measurements:
  • Grain bill weight
  • Weighted grain bill potential (can be swagged at 80% or 1.037 in most cases)
  • Strike water volume, corrected for temp
  • End of mash SG, before any sparge water added, and corrected for temp
  • Pre-boil volume, corrected for temp
  • Pre-boil SG, corrected for temp
  • Post-boil volume, corrected for temp
  • Post-boil SG (OG), corrected for temp
The calculated efficiencies can only be as accurate as your least accurate measurement, so being as accurate as possible is critical. End of mash and pre-boil SGs should be taken only after aggressive mixing in order to homogenize the wort so as to avoid false reading. Post-boil the wort is well homogenized due to boiling.

Since mash efficiency equals conversion efficiency times lauter efficiency, you need to be able to calculate both conversion efficiency and lauter efficiency in order to determine if your issue is due to low conversion, or lousy sparge. With the above measurements you will be able to calculate both.

Mash efficiency and conversion efficiency are both straight forward to calculate, and then lauter efficiency is calculated as:
Lauter Efficiency = Mash Efficiency / Conversion Efficiency​
You should target a conversion efficiency above 95%. Lauter efficiency will vary depending on lauter process and the ratio of grain bill weight to pre-boil volume. This variation is straight forward to calculate for batch or no-sparging, and can be estimated for fly sparging by calculating for a 3 or more batch sparge process. My spreadsheet for mash and sparge simulation is here. The lauter efficiency variation with grain bill size looks like the following:

Efficiency vs Grain to Pre-Boil Ratio for Various Sparge Counts.png


Brew on :mug:
 

RM-MN

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The most common cause of low conversion efficiency is too coarse a crush to convert in the allotted mash time. You can try to compensate for coarse crush by mashing longer, but the best solution is to get your own grain mill so you can control your crush. With BIAB, you don't have to worry about stuck lauters, so you can crush very fine (0.025" or finer.)
I'm not sure when I can get a mill, but if by next brew I can't, I'll ask my supplier to double or grain thinner, and explain to him the situation.

Good luck with getting the supplier to double mill or change their mill adjustment to suit you. It may happen, it may not.

I've been getting incredible brewhouse efficiency by using a Corona style mill and setting it as tight as I can. They aren't sexy but they are cheap and effective. Here's an example of the type of mill that I have.


Here's an example of how people have modified their Corona style mill.

 

RufusBrewer

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+1 what teddy4xp said.

In my world, the reason to be distracted by efficiency is to understand variables such that you can make the beer you like.

Too many home brewers worry about efficiency because *the higher the efficiency, the better of a brewer you are." This aint true.

Having said that, what can you do to optimize your efficiency?

Squeeze the bag before sparging.
Try a switch to dunk sparge
If you do do a pour, try opening the bag and pour all over the exposed grains.
BTW you are not doing a fly sparge.
Do what you can get a better finer grain crush
 

hottpeper13

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To see if it's the crush I would do a decoction mash striking in at the 64 temp you stated ,and bring it to 70. The extra time at 64 and the step should give you complete conversion and a very fermentable wort.
 

TkmLinus

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+1 to getting a mill and setting it to a fine crush. It is yet another piece of equipment to buy, but it will make a huge difference with your numbers. Good luck!
 

wsmith1625

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I also think it's the grain crush that attributed to your low gravity. If you can't get a grain mill right away, you can compensate poor efficiency with additional grain. I'm sure there's a formula to figure out how much is needed, but I'll leave that to someone who knows better.
 

odie

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crush finer.

mash longer.

open bag sparge.
 
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m3B.eer

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Hey Everyone,

I am re-opening this thread as I just did my 4th batch. And guess what? I'm still frustrated.

I asked my grain supplier if I could get a double mill or a finer crush, but his answer was negative. We discussed it, and well, as knowledgeable as he may seem, he simply told me my system was not efficient. lol. He said I should move to a mash tun. Anyways... I decided to give it one last go like this.

My grain bill was :
18lbs of Pilsner
1.1lbs of Buckwheat malt
1lbs of crushed buckwheat groat. + other adjuncts (acidulated malt and rice hulls).

Brewer's friend calculator, in my attempt to break a 10 gal batch, says I should get a 1.059 OG.

I also got a refractometer that I tried for the first time. I calibrated it with water, and took measurements at different times :
-At the end of mash, before sparge : 1.056
-After sparge/pre-boil (did a fly sparge again, with some help,which was done more accurately IMO) : 1.057
-After boil, while cooling down : 1.048.

All samples used were taken from the ball valve at the base of the keggle. I confirmed the last sample with the same sample and the hydrometer...

First : I'm surprised of this difference in readings... why is that?

Second... I'm still not able to hit target OG... which is frustrating... by maybe a full point again...

Any ideas? Or is it just "Get you own mill and mill your grain yourself..."?

Thank you
 

doug293cz

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Hey Everyone,

I am re-opening this thread as I just did my 4th batch. And guess what? I'm still frustrated.

I asked my grain supplier if I could get a double mill or a finer crush, but his answer was negative. We discussed it, and well, as knowledgeable as he may seem, he simply told me my system was not efficient. lol. He said I should move to a mash tun. Anyways... I decided to give it one last go like this.

My grain bill was :
18lbs of Pilsner
1.1lbs of Buckwheat malt
1lbs of crushed buckwheat groat. + other adjuncts (acidulated malt and rice hulls).

Brewer's friend calculator, in my attempt to break a 10 gal batch, says I should get a 1.059 OG.

I also got a refractometer that I tried for the first time. I calibrated it with water, and took measurements at different times :
-At the end of mash, before sparge : 1.056
-After sparge/pre-boil (did a fly sparge again, with some help,which was done more accurately IMO) : 1.057
-After boil, while cooling down : 1.048.

All samples used were taken from the ball valve at the base of the keggle. I confirmed the last sample with the same sample and the hydrometer...

First : I'm surprised of this difference in readings... why is that?

Second... I'm still not able to hit target OG... which is frustrating... by maybe a full point again...

Any ideas? Or is it just "Get you own mill and mill your grain yourself..."?

Thank you
First, SG measurements without the corresponding volume measurements are useless for doing diagnosis. The measurements you should take, and report when asking for help, are:
Strike water volume​
Volume of any other water added during the mash​
Sparge water volume​
Pre-Boil Volume​
Post-Boil Volume​
Fermenter Volume​
Ideally, all volume measurements will be corrected for thermal expansion back to equivalent room temperature volumes, for best accuracy. Accurate volume measurements are important, as the uncertainty in the efficiency values will be at least as large as the uncertainties in the volume measurements.

It is not possible for pre-boil SG to be higher than end of mash SG if you do a sparge. There have to be errors in measurement for this to occur. It is also not possible for post-boil SG to be lower than pre-boil SG. Again there have to be measurement errors if your data come out this way.

Can't offer any additional suggestions until you collect all of the needed data, and resolve your measurement error problem. One common problem with pre-boil SG measurements is failure to adequately mix the initial run-off wort with the sparged wort. If the total wort volume is not homogenized, it is possible to sample from a zone either higher or lower than the average (true) SG.

Sorry to be so blunt. I would really like to be able to offer you some helpful suggestions, but am unable to with missing and erroneous data.

Brew on :mug:
 
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m3B.eer

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Makes sense Doug.

i did not bother to express the volumes because I followed the exact same protocol as before.

Strike water to start at mash-in was 30L. Mashed in at 71C and mash help a temperature around 64-65C.
Added 3L during the mash.
Sparged with 14L of hot water, fly sparged.


I can not accurately measure my volume in my keggle but I nailed to fill my 10 gal keg, so I finished with a Fermenter volume is 9.5 gal.
From there I'd say post boil was 10.5, preboil 12gal. Shouldn't be too far off.

To explain the differences in gravity reading I understand not having mixed the wort could be an effect. Where do usually the sugar resides? Top or bottom?
I ,mentioned I did take them from the same spot as well.
 

marc1

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Makes sense Doug.

i did not bother to express the volumes because I followed the exact same protocol as before.

Strike water to start at mash-in was 30L. Mashed in at 71C and mash help a temperature around 64-65C.
Added 3L during the mash.
Sparged with 14L of hot water, fly sparged.


I can not accurately measure my volume in my keggle but I nailed to fill my 10 gal keg, so I finished with a Fermenter volume is 9.5 gal.
From there I'd say post boil was 10.5, preboil 12gal. Shouldn't be too far off.

To explain the differences in gravity reading I understand not having mixed the wort could be an effect. Where do usually the sugar resides? Top or bottom?
I ,mentioned I did take them from the same spot as well.

Calibrate a stick. I use a wooden spoon.

20220117_003849.jpg
 

doug293cz

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Makes sense Doug.

i did not bother to express the volumes because I followed the exact same protocol as before.

Strike water to start at mash-in was 30L. Mashed in at 71C and mash help a temperature around 64-65C.
Added 3L during the mash.
Sparged with 14L of hot water, fly sparged.


I can not accurately measure my volume in my keggle but I nailed to fill my 10 gal keg, so I finished with a Fermenter volume is 9.5 gal.
From there I'd say post boil was 10.5, preboil 12gal. Shouldn't be too far off.

To explain the differences in gravity reading I understand not having mixed the wort could be an effect. Where do usually the sugar resides? Top or bottom?
I ,mentioned I did take them from the same spot as well.
The first few times you use a refractometer, you should also check all measurements with a hydrometer. After you can consistently get the measurements to agree, you no longer have to verify all refractometer measurements with the hydrometer.

If the sparge wort is not mixed with the initial wort, then you are likely to have the higher gravity wort at the bottom of the kettle. This could explain why your post-sparge SG reading was essentially identical to your end of mash reading.

The best way to calibrate a dipstick is to add a gallon of water at a time to your vessel, and then mark the stick. Repeat until you have the vessel capacity marked on the stick. The most accurate way to measure a gallon of water is to weigh it with a scale that has a precision of 0.01 lb. Water at room temperature weighs 8.33 lb/gal.

I'll try working with the numbers you have in the morning, to see if I can discern anything about your efficiency.

Brew on :mug:
 

RM-MN

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I asked my grain supplier if I could get a double mill or a finer crush, but his answer was negative. We discussed it, and well, as knowledgeable as he may seem, he simply told me my system was not efficient. lol. He said I should move to a mash tun. Anyways... I decided to give it one last go like this.
Any ideas? Or is it just "Get you own mill and mill your grain yourself..."?

With a supplier with that attitude I would be looking for a different supplier. The grain mill is also recommended.

Where do usually the sugar resides? Top or bottom?

If you were to look in the beginners forum you might see where extract brewers will complain about their OG being very low. That's because they use a malt extract and top off water. The concentrated wort produced during the boil doesn't want to be mixed with the top off water.

When you mash your grain, the sugars are denser than water and will settle towards the bottom. I have experimented with my refractometer and pipette and will get quite different readings between right at the top and 4" (the limit of the pipette) down. When you draw off the bottom of the keggle you get the highest concentration of sugars. Take it off the top and you will get the lowest. That's where the drop in reading between your preboil and post boil comes from.
 

madscientist451

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. I'm still not able to hit target OG... which is frustrating... by maybe a full point again...

Any ideas? Or is it just "Get you own mill and mill your grain yourself..."?

Thank you

You have several options as you go forward:
-Already stated: Get your own mill. I run my grain though twice when I'm BIAB brewing. If money is tight, look around for used stuff, there's always someone selling homebrew gear.
-Until you get a mill, accept the efficiency you are getting, and change your grain bill to make up for it; throwing a pound or two more of base malt in to your brew would be an easy fix.
-Have some DME on hand to throw in the end of the boil if your post boil gravity is low. You could also add table sugar or a combination of DME/Sugar
-Boil longer (but then you'll have less volume)
-Try using your ball valve to run off the first runnings to a bucket. Then add your sparge water to the kettle with the bag in place and stir it up some. Pull your grains out and add your first runnings back in.
 

TkmLinus

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Are you squeezing the bag to get as much wort as you can after your mash before sparging? When I sparge, I place the bag in another empty kettle, pour in the water, then give it a good mix and drain. No need to heat the sparge water, since all we are doing is essentially rinsing the grains.

By the way, I picked up a cereal killer mill($100.00 at austin homebrew, link below) and after setting the gap to 0.025" my efficiency jumped from 60-65 to 80-85%, my OG on kits is consistently above the estimates. After getting the mill I wished I had picked it up sooner. Cereal Killer Grain Mill
 

wsmith1625

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I think I have a solution for you until you get a grain mill. Buy your grain online. I buy all my ingredients online because I don't have a local homebrew shop. A lot of shops will double crush the grain if you request it. Also, many shops have free or flat rate shipping when your order hits a certain price point. I usually order several recipes at once to take advantage of this.

I order uncrushed grain now and use several online shops depending on what promotions are running, but my go-to favorite shop is Atlantic Brew Supply. Great prices, great team, and fast shipping here on the east coast.
 
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m3B.eer

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-Boil longer (but then you'll have less volume)
-Try using your ball valve to run off the first runnings to a bucket. Then add your sparge water to the kettle with the bag in place and stir it up some. Pull your grains out and add your first runnings back in.

I like this idea. would be a bit more work obviously, and need more material,to fit my 30L+ of first runnings. Then basically batch sparge... I could definitely try this.

Are you squeezing the bag to get as much wort as you can after your mash before sparging? When I sparge, I place the bag in another empty kettle, pour in the water, then give it a good mix and drain. No need to heat the sparge water, since all we are doing is essentially rinsing the grains.

Oh yeah. Big squeeze, I spend quite a bite of time after the sparge and until the boil arrives pressing the bag as much as I can.

It may also be that the bag I use has a finer mesh than the one I used to use on my 5Gal batches...

I guess I'll be looking slowly into my own mill then. I recently moved to kegging, and it feels like needed things keep adding up and adding up...it's endless... lol. Need more space, and money obviously.

I'm in Canada and don't know many online shops, but can take a look. I usually plan my recipes quite on the fly, and like to get my ingredients and brew them quickly after. More planning would then be needed...

Thanks to all of you for the suggestions.
 

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...

Oh yeah. Big squeeze, I spend quite a bite of time after the sparge and until the boil arrives pressing the bag as much as I can.

..
You'll get more extract for your effort (more bang for the buck) if you squeeze prior to the sparge rather than after the sparge, but both is best. The wort squeezed prior to sparging is much higher SG than wort recovered by squeezing after sparging. As far as efficiency goes, from worst to best:
  • No squeeze
  • Squeeze after sparge only
  • Squeeze before sparge only
  • Squeeze before and after sparge.
Brew on :mug:
 

doug293cz

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Hey Everyone,

I am re-opening this thread as I just did my 4th batch. And guess what? I'm still frustrated.

I asked my grain supplier if I could get a double mill or a finer crush, but his answer was negative. We discussed it, and well, as knowledgeable as he may seem, he simply told me my system was not efficient. lol. He said I should move to a mash tun. Anyways... I decided to give it one last go like this.

My grain bill was :
18lbs of Pilsner
1.1lbs of Buckwheat malt
1lbs of crushed buckwheat groat. + other adjuncts (acidulated malt and rice hulls).

Brewer's friend calculator, in my attempt to break a 10 gal batch, says I should get a 1.059 OG.

I also got a refractometer that I tried for the first time. I calibrated it with water, and took measurements at different times :
-At the end of mash, before sparge : 1.056
-After sparge/pre-boil (did a fly sparge again, with some help,which was done more accurately IMO) : 1.057
-After boil, while cooling down : 1.048.

All samples used were taken from the ball valve at the base of the keggle. I confirmed the last sample with the same sample and the hydrometer...

First : I'm surprised of this difference in readings... why is that?

Second... I'm still not able to hit target OG... which is frustrating... by maybe a full point again...

Any ideas? Or is it just "Get you own mill and mill your grain yourself..."?

Thank you

Makes sense Doug.

i did not bother to express the volumes because I followed the exact same protocol as before.

Strike water to start at mash-in was 30L. Mashed in at 71C and mash help a temperature around 64-65C.
Added 3L during the mash.
Sparged with 14L of hot water, fly sparged.


I can not accurately measure my volume in my keggle but I nailed to fill my 10 gal keg, so I finished with a Fermenter volume is 9.5 gal.
From there I'd say post boil was 10.5, preboil 12gal. Shouldn't be too far off.

To explain the differences in gravity reading I understand not having mixed the wort could be an effect. Where do usually the sugar resides? Top or bottom?
I ,mentioned I did take them from the same spot as well.
Ok, you used ~22.25 lb of grain and 30+3 L (8.72 gal) of water in the mash. Assuming a weighted grain potential of 36.5 ppg (pilsner @ 37 and buckwheat @ 31), the end of mash SG should have been 1.077 - 1.078 @ 100% conversion efficiency. Your value of 1.056 would put conversion efficiency at 69 - 70%.

If you can't get finer grain crush you should mash longer to get more conversion. To determine your required mash time, sample the SG in the mash (after an aggressive stir) after 60 minutes, and then measure again (after stir) at 15 minute intervals. When the SG stops increasing between samples, you have gotten as much conversion as you are going to get. Make sure you stir well before sampling, or you could get erroneous measurements due to inhomogeneous wort. If you see the SG go down from sample to sample, that means you are not stirring enough prior to sampling (i.e. you've been sampling inhomogeneous wort), or your refractometer technique needs to be improved.

Can't say too much about the rest of you process as SG measurements are inconsistent, and the volume measurements cannot be reconciled with each other under required constraints.

Brew on :mug:
 

madscientist451

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Another option I didn't mention, and its related to doug's post above is to do an overnight or all day mash. Get your mash started, hitting your desired mash temp, then wrap the keggle up un an old sleeping bag, winter coat or whatever you have and don't mess with it for about 8 hours. Do it at night and go to bed, get it going before work, whatever, and then pull a sample when its done and check your gravity. Note that this process may result in a lower attenuating beer than the recipe calls for.
 

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Another option I didn't mention, and its related to doug's post above is to do an overnight or all day mash. Get your mash started, hitting your desired mash temp, then wrap the keggle up un an old sleeping bag, winter coat or whatever you have and don't mess with it for about 8 hours. Do it at night and go to bed, get it going before work, whatever, and then pull a sample when its done and check your gravity. Note that this process may result in a lower attenuating beer than the recipe calls for.
If by "lower attenuating" you mean attenuate to a lower FG (i.e. more fermentable), then yes.

Brew on :mug:
 

madscientist451

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Yeah I guess I should have said "more attenuation"? But what I found with overnight mashes is that the FG does go lower, which is OK in some situations, but not OK in others.
 

RM-MN

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Yeah I guess I should have said "more attenuation"? But what I found with overnight mashes is that the FG does go lower, which is OK in some situations, but not OK in others.

Whether the FG goes lower in an overnight mash depends on whether or not the conversion was complete before the temperature fell or not. If there was still unconverted starches, such as in a coarse crush, then conversion will continue with the temperature drop and then beta amylase will be more dominant. If you convert all starches with the temperature stable, beta amylase won't survive long enough to make the wort more fermentable.
 

madscientist451

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Doing BIAB on my smooth surface electric range, the temperature stays pretty stable for and hour or more then starts going down. I noticed higher SG (more conversion) and also lower FG. My drafty old house is pretty chilly in the winter when I turn the heat down at night, so in my case the overnight mashing is somewhat unpredictable, so I seldom use it anymore, but for the OP it may help solve some of the problems described.
 

Bobby_M

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There really is no way to effectively fly sparge grain in a bag. It may seem like it works from a big picture perspective, but the mechanics really only work in a vessel that is being drained. A stirred dunk sparge (batch sparge from a calculation/software perspective)

It's unfortunate that your grain supplier was so closed off to the idea of double milling. It's likely the person has never deviated from multi-vessel brewing and just doesn't want to hear it. What I would say to them is that if they are not willing to take the extra 2 minutes to run the grain through one more time, you will be finding a supplier that will. They are out there. If my customers ask for it, I'll turn their grain into 90% flour.

The last thing to consider is a shift in expectations. When you say that you're missing your numbers, a better way to say it is that your expected numbers were inflated. Your system efficiency is unique to you and recipes that you import must be scaled to your system. If the recipe says use this amount of grain for 1.060 OG, it's in relation to a stated efficiency. You adjust that efficiency to your system and use whatever grain plus/minus required.
 

Sam_92

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You said you are using an electric keggle and maintaining the mash temp over the hour so I'm assuming you have a heating element at the bottom and a temp probe into the kettle somewhere. Are you taking temperature readings with a standard thermometer or trusting the temp probe? Did you calibrate the temperature probe? Where is the temperature probe in relation to the heating element?

I'm wondering if maybe your temp probe is up in the middle of the mash and calling for more heat when at the bottom of the temperature is high enough to denature enzymes from the bottom up. I have a very small electric kettle I built and I've seen it do things like that.
 
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