Help with Mash Recirculation

[jwalkermed]

I'm late to this thread but I'll chime in. I use a recirculating system that I built and for the last couple of batches I've had the stuck BIAB issue described here. I have done a total of 9 brews on the system and only had the issue on the last 2. Haven't changed a thing with my process. I'm wondering if over time proteins/junk whatever coagulate on the bag mesh and cause restriction of flow? I may pick up a new bag for my next brew to test the theory. I'm using "the brew bag" bag if.

 

[hafmpty]

As I'm reading this (as a newer BIABer) I'm thinking about "efficiency" with BIAB systems. Correct me if I'm wrong, but as long as you crush your malt appropriately (whether at .050 or .005) and give the mash the proper time & temperature, you'll always get 100% conversion efficiency (or very near 100%). A starch test will certainly verify conversion.

But once your conversion is complete, your gravity will not change. At the end of your mash, if you take a gravity sample, that is your pre-boil gravity. Even before you remove the bag/basket/grain, you're still seeing your pre-boil gravity.
This is true IF your wort is sufficiently mixed (which happens with a recirculating system).

From there, the only thing that will effect your "Brewhouse Efficiency" is the amount of pre-boil wort you have left in the pot after you remove your bag/basket/grain. This is affected by how well you "drain your wort" out of the grain.

I don't squeeze, crush looser, and get 80%. Help me see my errors in thinking, but that number has to do with the drainage of the wort from the grain...not the crush. Again, as long as the grain is crushed and is given sufficient time at the right temperature, your "conversion efficiency" will be 100%. If you and your system used the same amount of water and grain as me and my system...if we both get 100$ conversion, we would have the same pre-boil gravity after the mash was completed. We would both have 100% "conversion efficiency."

From there, if you ended up with 5.5 gallons in the kettle after you removed your grain and I ended up with 5.3 gallons, your "brewhouse efficiency" would be better...your "drainage" is better and so it affected your overall "brewhouse efficiency."

I say this mostly for my own clarity of thinking. Am I seeing it right?

 

[thekraken]

Looks about right to me. Except maybe don't expect to be able to achieve max conversion efficiency if the crush is too course, no matter how long you mash.

I suspect you've already seen this but in case you haven't: http://www.braukaiser.com/wiki/index.php?title=Understanding_Efficiency

 

[TexasWine]

From there, the only thing that will effect your "Brewhouse Efficiency" is the amount of pre-boil wort you have left in the pot after you remove your bag/basket/grain.

Don't forget hop absorption!

 

[Gavin C]

+1

and lets not forget

kettle/chiller/hoses deadspace (if you use them)

kettle trub

spills

gravity samples (if any taken and not returned)

There are different ways to acount for these losses of sugar in different brewing software.

 

[hafmpty]

I know now why talking about "efficiency" can be so confusing. I thought I was using the proper terms, but I wasn't. When I said, "Brewhouse Efficiency" I should have said, "Pre-Boil Efficiency." Here's the terms I need to use to describe what I'm talking about taken from BrewersFriend.com:

Conversion Efficiency - The percentage of total available sugars that were extracted from the grains inside the mash tun. This is the gravity measured before the boil. The volume does not count grain absorption or mash tun dead space.

Pre-Boil Efficiency - The percentage of total available sugars that made it into the kettle. The gravity is measured before the boil. The volume is how much wort went into the kettle.

Ending Kettle Efficiency - The percentage of total available sugars that made it to the end of the boil, before draining the kettle. Gravity is measured as OG after cooling, before pitching yeast. Volume is measured as the ending kettle volume when cooled, before draining.

Brew House Efficiency - An all inclusive measure of efficiency, which counts all losses to the fermentor. This can be thought of as 'to the fermentor' efficiency. Hops absorption factors into this. Gravity is measured as OG after cooling, before pitching yeast. Volume is how much wort went into the fermentor.

Using the terms above, my earlier post should have said:

As long as you crush your malt appropriately (whether at .050 or .005) and give the mash the proper time & temperature, you'll always get 100% CONVERISON EFFICIENCY (or very near 100%). A starch test will certainly verify conversion.

But once your conversion is complete, your gravity will not change. At the end of your mash, if you take a gravity sample, that is your pre-boil gravity. Even before you remove the bag/basket/grain, you're still seeing your pre-boil gravity.
This is true IF your wort is sufficiently mixed (which happens with a recirculating system).

From there, the only thing that will effect your PRE-BOIL EFFICIENCY is the amount of wort you lose that is retained/absorbed by the grain that you can't get out. This is affected by how well you "drain your wort" out of the grain.

Your PRE-BOIL EFFICIENCY in a BIAB system has to do with the drainage of the wort from the grain...not the crush. All things being equal (water amounts/grain bill/mash time/mash temp) if you ended up with more pre-boil wort in the kettle (after removing the bag/basket/grain) your PRE-BOIL EFFICIENCY would be better because your "drainage" is better.

So...

I tried a coarser crush this weekend...my mash efficiency has been right around 85%, but when I increased the crush, it dropped to 75% (60-minute mash). I didn't measure the conversion, so I don't know if longer mashing would have increased the efficiency, but it definitely was worse for the same length of time.

To help me (and others) know what you're talking about, what type of "efficiency" are you referring too? Was your pre-boil gravity lower than expected? Did you end up with less wort (so a higher absorption rate)? Just trying to understand. Thanks!

I had the same experience yesterday. Missed my gravity and was about 10% lower in efficiency than normal, but with my usual 30 minute mash.

What type of "efficiency" are you talking about? Did you sparge? Did your pre-boil/post bag pull gravity come in lower? Thanks!

 

[cantrell00]

Extraction efficiency (% or sugar that lands in kettle from mash) is the most pertinent variable.

The remaining losses are much easier to predict.

When taking about brewhouse efficiency, in the real world, you really are talking about mashing efficiency.

In my opinion.

 

[Gavin C]

• Mash efficiency (conversion efficiencyx lauter efficiency)
  
• Brewhouse efficiency

The two can be very different. Certainly not the same thing

here is a thread/article that may be helpful.

It was written with this type of discussion/confusion/peoples personal definitions in mind.

There are absolute definitions of the terms. They are not synonymous.

 

[cantrell00]

• Mash efficiency (conversion efficiencyx lauter efficiency)
  
• Brewhouse efficiency

The two can be very different. Certainly not the same thing

here is a thread/article that may be helpful.

It was written with this type of discussion/confusion/peoples personal definitions in mind.

There are absolute definitions of the terms. They are not synonymous.

Aware.

In a practical sense though, extraction efficiency is the biggest variable that influences the overall brewhouse efficiency. By far, in my experience.

 

[doug293cz]

I know now why talking about "efficiency" can be so confusing. I thought I was using the proper terms, but I wasn't. When I said, "Brewhouse Efficiency" I should have said, "Pre-Boil Efficiency." Here's the terms I need to use to describe what I'm talking about taken from BrewersFriend.com:

Conversion Efficiency - The percentage of total available sugars that were extracted from the grains inside the mash tun. This is the gravity measured before the boil. The volume does not count grain absorption or mash tun dead space.

Basically correct. It's more than just the SG of the wort in the mash. It's a combination of the SG and actual wort volume (which is greater than the strike water volume due to the volume of the sugar dissolved in the wort) compared to the maximum possible SG at the actual wort volume.

Pre-Boil Efficiency - The percentage of total available sugars that made it into the kettle. The gravity is measured before the boil. The volume is how much wort went into the kettle.

This is also commonly known as "Mash Efficiency." There is also a "Lauter Efficiency" which is the percentage of the wort in the mash that actually makes it into the BK. This is where grain absorption and undrainable MLT volume affect efficiency.

Mash Efficiency = Conversion Efficiency * Lauter Efficiency​

Ending Kettle Efficiency - The percentage of total available sugars that made it to the end of the boil, before draining the kettle. Gravity is measured as OG after cooling, before pitching yeast. Volume is measured as the ending kettle volume when cooled, before draining.

This should be the same as mash (pre-boil) efficiency, unless you lost volume due to boil overs, wort samples, etc. You don't boil off any of the sugar.

Brew House Efficiency - An all inclusive measure of efficiency, which counts all losses to the fermentor. This can be thought of as 'to the fermentor' efficiency. Hops absorption factors into this. Gravity is measured as OG after cooling, before pitching yeast. Volume is how much wort went into the fermentor.

This is the definition of Brew House Efficiency that BeerSmith and Brewer's Friend use. Although there are some who define it differently, which leads to much confusion.

Using the terms above, my earlier post should have said:

As long as you crush your malt appropriately (whether at .050 or .005) and give the mash the proper time & temperature, you'll always get 100% CONVERISON EFFICIENCY (or very near 100%). A starch test will certainly verify conversion.

But once your conversion is complete, your gravity will not change. At the end of your mash, if you take a gravity sample, that is your pre-boil gravity. Even before you remove the bag/basket/grain, you're still seeing your pre-boil gravity.
This is true IF your wort is sufficiently mixed (which happens with a recirculating system).

From there, the only thing that will effect your PRE-BOIL EFFICIENCY is the amount of wort you lose that is retained/absorbed by the grain that you can't get out. This is affected by how well you "drain your wort" out of the grain.

Your PRE-BOIL EFFICIENCY in a BIAB system has to do with the drainage of the wort from the grain...not the crush. All things being equal (water amounts/grain bill/mash time/mash temp) if you ended up with more pre-boil wort in the kettle (after removing the bag/basket/grain) your PRE-BOIL EFFICIENCY would be better because your "drainage" is better.

I agree with your analysis.


Brew on

 

[Gavin C]

Aware.

In a practical sense though, extraction efficiency is the biggest variable that influences the overall brewhouse efficiency. By far, in my experience.

i'm not sure what you mean by extraction efficiency.

Are you using it to describe conversion efficiency or mash efficiency or some other hybrid term? This is a perfect example of the confusion inherrent in written discussions on the topic. People use different terms but are describing the same thing.

I think the two very useful figures to know are mash efficiency (how much sugars make it to the boil-kettle) and brewhouse efficiency (how much sugars make it to the FV)

If someone is having problems in the brewery then examining conversion efficiency and lauter efficiency is the obvious first step. You gotta look at both to see where an issue lies.

This is the crux of the issue with recirculation it seems. Upping conversion efficiency with a finer milling can impact lautering in a recirculating system perhaps. Finding the sweet spot between the two to optimise performance and consistency would seem to be the issue at hand.

In that sense it is important to use the correct terms appropriately.

 

[cantrell00]

i'm not sure what you mean by extraction efficiency.

Are you using it to describe conversion efficiency or mash efficiency or some other hybrid term? This is a perfect example of the confusion inherrent in written discussions on the topic. People use different terms but are describing the same thing.

I think the two very useful figures to know are mash efficiency (how much sugars make it to the boil-kettle) and brewhouse efficiency (how much sugars make it to the FV)

If someone is having problems in the brewery then examining conversion efficiency and lauter efficiency is the obvious first step. You gotta look at both to see where an issue lies.

This is the crux of the issue with recirculation it seems. Upping conversion efficiency with a finer milling can impact lautering in a recirculating system perhaps. Finding the sweet spot between the two to optimise performance and consistency would seem to be the issue at hand.

In that sense it is important to use the correct terms appropriately.

I specifically mentioned sugars making it to the kettle.

 

[Gavin C]

I specifically mentioned sugars making it to the kettle.

I saw that, but wasnot sure as it is not a term I have heard before. Thanks for the clarification.

Mash efficiency then. Cool

 

[cantrell00]

I saw that, but wasnot sure as it is not a term I have heard before. Thanks for the clarification.

Mash efficiency then. Cool

Sorry.. You are right. It really is semantics when you are knowledgeable.

When you aren't, I can see that it could become very confusing.

The concepts really aren't confusing though. Well, no more than any other ratio.

 

[dunbruha]

Before you give up on the coarser crush, compare the flavor of this beer to one that you made with the finer crush and report the results. I'm curious about the final product.:rockin:

It's bubbling away right now, so I'll see in a few weeks.

 

[1MadScientist]

schiersteinbrewing, I like your mash recirculation arm. Would you describe more about it, number of holes, how much of it is below the mash, etc...

I need to measure my flow rate, at the lowest setting it's 10 L/Min at 0 head and 5 L/Min at 1 meter of head. I want a slow flow rate like you.

MS

 

[schiersteinbrewing]

With 8gal of water and 9lbs of grain it sits about 3.5-4 inches below the mash. With 12gal of water and 14lbs of grain it is fully submerged. The part above the green o-ring is a piece of copper soldered onto the threads to act as a spacer so I can tighten it down to the lid.

I want to remake it to where it goes to the center of the kettle and sprays out all around, and make the spacer a little nicer looking. Possibly have it come in the side of the kettle to make removing the lid easier. Right now I just use the grain bucket to set the lid on, and the arm drips into the bucket.

I just adjust the flow to where it looks right. I use a chugger pump with a ball valve on the output to control the flow. The last image is an older one before cam locks and this recirc arm but it will give you an idea on the setup and pump.

 

[1MadScientist]

Thank you. I want to make one of those now.

 

[Gavin C]

With 8gal of water and 9lbs of grain it sits about 3.5-4 inches below the mash. With 12gal of water and 14lbs of grain it is fully submerged. The part above the green o-ring is a piece of copper soldered onto the threads to act as a spacer so I can tighten it down to the lid.

I want to remake it to where it goes to the center of the kettle and sprays out all around, and make the spacer a little nicer looking. Possibly have it come in the side of the kettle to make removing the lid easier. Right now I just use the grain bucket to set the lid on, and the arm drips into the bucket.

I just adjust the flow to where it looks right. I use a chugger pump with a ball valve on the output to control the flow. The last image is an older one before cam locks and this recirc arm but it will give you an idea on the setup and pump.

That's a great setup there. Thanks for showing the detailed images. Is that a DIY COFI of sorts then?

 

[schiersteinbrewing]

That's a great setup there. Thanks for showing the detailed images. Is that a DIY COFI of sorts then?

Pretty much.

 

[schiersteinbrewing]

Just bought a Bayou Classic FB to, test flow with.

http://www.amazon.com/dp/B00CAAD1D6/?tag=skimlinks_replacement-20

Still working on the plan to make it fit and beef up/redo the FB supports.

 

[schiersteinbrewing]

I just cut about a 1/4in off each side so it would slide in. Fit is pretty good.
View attachment ImageUploadedByHome Brew1443402178.023436.jpg
View attachment ImageUploadedByHome Brew1443402198.593036.jpgView attachment ImageUploadedByHome Brew1443402209.976460.jpg

 

[hafmpty]

OK. I brewed two back-to-back batches on Monday. Two different beers so that's obviously a variable. Here are my results:

BATCH 1
Brewing Classic Styles - Triple-X
5.6gal of Strike Water - 7lbs 1oz of Grain

0min - 7.2/7.3 brix
10min - 8.6/8.7 brix
20min - 9.4/9.5 brix
30min - 10/10.1 brix - I stirred the mash at this point
40min - 10.1/10.2 brix
50min - 10.5/10.6 brix
60min - 10.5/10.6 brix
After 10min Mash Out - 10.8/10.9

My thoughts on the sudden rise in gravity during Mash Out...I wonder if the more viscous wort allows the "trapped" sugars in the grain to go into solution? Not sure. Thoughts?

BATCH 2
Brewing Classic Styles - English Ordinary Bitter - No Short Measure
5.4gal of Strike Water - 5lbs 8oz of Grain

Immediately After Dough-In - 3.4 brix
After Stirring (i.e. 0min) - 4.6 brix
45min - 5.2 brix (Stirred)
30min - 6.2 brix (Stirred) - Checked Conversion w/ Iodophor - Conversion Complete
15min - 6.7 brix
0min - 6.8 brix
After 5min Into Mash Out - 7.2 brix
After 15min Mash Out - 7.2 brix

Thoughts? I found it interesting that conversion was tested as complete at 30 minutes but the gravity still continued to rise. I tested it twice to verify that it was indeed complete. What's up with that?

 

[iijakii]

That's very interesting to me. That's a significant raise, not sure you can attribute that to mash-out. Ive personally never measured gravity until after I've drained/sparged so I can't attest to if there's something finicky with those readings.

 

[doug293cz]

Did you stir prior to each gravity sample? If not, the wort gravity might not have been uniform throughout the mash. Uniformity is key to getting good data. All of the sugar is in solution when it is created, but there are very likely to be concentration gradients in the wort, especially around any wort trapped in pores of the grits.

Iodine tests can mislead in two ways:

1. If only the wort is sampled, starch can remain in the grits which will not show up in the tests
2. The polysaccharides remaining in the mash can be too sort to change the color of the iodine but still not have reached the point where all that's left is limit dextrines

Brew on

 

[hafmpty]

Did you stir prior to each gravity sample?

For the first mash I did not. I only stirred at the 30 minute mark. The second mash, I stirred where noted.

Iodine tests can mislead...

Definitely! Which is part of the reason I wanted to test it. I mash for 60min. But I wanted to see if I could get the same rate of conversion from grain crushed at .050 as someone who crushes much tighter.

As far as the "visual conversion" test, it was "converted" at 30min. But like you say, the visual test doesn't actually indicate that I've truly converted all the starches into sugar. That's why with whatever crush, I default to the 60min mash.

For next brew day, I will keep a better process. I'm thinking gravity checks every 10min offset with stirring in between...

0min - Dough-In & Stir
5min - Gravity Check
10min - Stir
15min - Gravity Check
20min - Stir
25min - Gravity Check
30min - Stir
35min - Gravity Check
40min - Stir
45min - Gravity Check
50min - Stir
55min - Gravity Check
60min - Stir & Mash-Out
Mash-Out 5min - Gravity Check
Mash-Out 10min - Stir
Mash-Out 15min - Gravity Check

 

[Gavin C]

OK.here's my great data set. What's up with that?

Thanks for sharing this interesting data. Much appreciated.

 

[1MadScientist]

OK. I brewed two back-to-back batches on Monday. Two different beers so that's obviously a variable. Here are my results:

BATCH 1
Brewing Classic Styles - Triple-X
5.6gal of Strike Water - 7lbs 1oz of Grain

0min - 7.2/7.3 brix
10min - 8.6/8.7 brix
20min - 9.4/9.5 brix
30min - 10/10.1 brix - I stirred the mash at this point
40min - 10.1/10.2 brix
50min - 10.5/10.6 brix
60min - 10.5/10.6 brix
After 10min Mash Out - 10.8/10.9

My thoughts on the sudden rise in gravity during Mash Out...I wonder if the more viscous wort allows the "trapped" sugars in the grain to go into solution? Not sure. Thoughts?

BATCH 2
Brewing Classic Styles - English Ordinary Bitter - No Short Measure
5.4gal of Strike Water - 5lbs 8oz of Grain

Immediately After Dough-In - 3.4 brix
After Stirring (i.e. 0min) - 4.6 brix
45min - 5.2 brix (Stirred)
30min - 6.2 brix (Stirred) - Checked Conversion w/ Iodophor - Conversion Complete
15min - 6.7 brix
0min - 6.8 brix
After 5min Into Mash Out - 7.2 brix
After 15min Mash Out - 7.2 brix

Thoughts? I found it interesting that conversion was tested as complete at 30 minutes but the gravity still continued to rise. I tested it twice to verify that it was indeed complete. What's up with that?

I'm trying to draw some data based on those 2 brews. I noticed that the grain bills are much lower than the book. What batch size do you make?, more specifically what was your volume at flame out? On page 41, recipes are designed to leave 6 gallons of wort in the kettle at the end of the boil. I want to see how your 0.050" crush faired (efficiency wise). Can you provide beginning or end of boiling volumes and OG sets to determine efficiency?

 

[schiersteinbrewing]

Definitely! Which is part of the reason I wanted to test it. I mash for 60min. But I wanted to see if I could get the same rate of conversion from grain crushed at .050 as someone who crushes much tighter.

So for both brews your crush was at .050?

 

[doug293cz]

For the first mash I did not. I only stirred at the 30 minute mark. The second mash, I stirred where noted.



Definitely! Which is part of the reason I wanted to test it. I mash for 60min. But I wanted to see if I could get the same rate of conversion from grain crushed at .050 as someone who crushes much tighter.

As far as the "visual conversion" test, it was "converted" at 30min. But like you say, the visual test doesn't actually indicate that I've truly converted all the starches into sugar. That's why with whatever crush, I default to the 60min mash.

For next brew day, I will keep a better process. I'm thinking gravity checks every 10min offset with stirring in between...

0min - Dough-In & Stir
5min - Gravity Check
10min - Stir
15min - Gravity Check
20min - Stir
25min - Gravity Check
30min - Stir
35min - Gravity Check
40min - Stir
45min - Gravity Check
50min - Stir
55min - Gravity Check
60min - Stir & Mash-Out
Mash-Out 5min - Gravity Check
Mash-Out 10min - Stir
Mash-Out 15min - Gravity Check

That protocol should give more consistent data, but I would suggest taking the gravity samples immediately after stirring in order to minimize the time for any new concentration gradients to develop.

Brew on

 

[hafmpty]

So for both brews your crush was at .050?

Yes I used .050 for both batches.

I'm trying to draw some data based on those 2 brews. I noticed that the grain bills are much lower than the book. What batch size do you make?, more specifically what was your volume at flame out? On page 41, recipes are designed to leave 6 gallons of wort in the kettle at the end of the boil. I want to see how your 0.050" crush faired (efficiency wise). Can you provide beginning or end of boiling volumes and OG sets to determine efficiency?

I brew 2.5gal batches (actually into the keg). My pre-boil gravity for the Triple X was 1.044 (without Lactose) with 5gal in the pot pre-boil and 3.75gal 1.070 POST-chill (with Lactose).

The second batch was 4.9-ish gallons in the pot with 1.028/9 pre-boil and 1.038 with 3.75-ish gallons POST-chill.

BTW I scale the recipes with the same amounts by percentage.

My profile is to begin the boil with 4.75gal in the pot and end with 3.75gal (Both batches ended up with more pre-boil wort. I'm still working on my grain absorption & boil off percentages). Don't know if it's helpful or not but I used 5.6gal of strike water in the Triple X. And the Bitter used 5.4gal of strike water.

I was mistaken above with my grain bill weight for the bitter. I didn't have enough Maris Otter so I supplemented with 2-row and Munich. I used 3lbs 8oz of Maris Otter, 7oz of 2-row and 1oz of Munich. I realized as I was writing this that the changes I made to the grain bill should have resulted in more of these malts being used, but my calculations were off. All the rest of the grains percentages were the same.

By my calculations using Brewers Friend is got 78.36% efficiency on the Triple X and 83.68% efficiency on the Bitter.

I don't have my brew notebook in front of me, but I'm 99% sure of these numbers. I'll look later when I get home to verify.

 

[hafmpty]

I would suggest taking the gravity samples immediately after stirring in order to minimize the time for any new concentration gradients to develop.

I think what I'll do it take a sample and then stir...trying the stir in the same/similar way each time.

 

[TexasWine]

I think what I'll do it take a sample and then stir...trying the stir in the same/similar way each time.

You'll need to stir then sample. Otherwise you won't get a proper reading.

 

[hafmpty]

You'll need to stir then sample. Otherwise you won't get a proper reading.

Why would that order get a proper sample? If I sample first I'd get the reading "as is." Then I stir and give the mash 10min of recirculating to get to "equilibrium" again.

I don't care either way...I'm trying to understand why stirring first is better?

Maybe it's because I'm thinking take a sample from the recirculation port vs. from just somewhere in mash?

 

[thekraken]

That protocol should give more consistent data, but I would suggest taking the gravity samples immediately after stirring in order to minimize the time for any new concentration gradients to develop.

Brew on

I'm having trouble conceptualizing why concentration gradients would develop. They are recirculating after all.

Why would that order get a proper sample? If I sample first I'd get the reading "as is." Then I stir and give the mash 10min of recirculating to get to "equilibrium" again.

I don't care either way...I'm trying to understand why stirring first is better?

Maybe it's because I'm thinking take a sample from the recirculation port vs. from just somewhere in mash?

I'm thinking that this would be fine. I guess, in any case the best thing is to be consistent.

 

[TexasWine]

Why would that order get a proper sample? If I sample first I'd get the reading "as is." Then I stir and give the mash 10min of recirculating to get to "equilibrium" again.

I don't care either way...I'm trying to understand why stirring first is better?

Maybe it's because I'm thinking take a sample from the recirculation port vs. from just somewhere in mash?

Well, for some reason forgot that this was a thread all about recirculating. So i would say that stirring in this case should provide little to no benefit! My apologies.

To test this theory, I would be interested to know if you (we) would get a different reading before and after stirring. If you have a refractometer you should be able to easily pull a sample from the recirculation port, stir, then pull another sample from somewhere in the middle of the grain bed.

I've got too many things I'm supposed to be testing during the course of my brew days!!!

 

[IDrinkBr]

This thread has gotten a little off-topic but I thought I'd chime in again as well.

Since I started BIAB with my RIMS tube I have been taking readings during my mash.

I take readings with my refractometer at 5 minute intervals and stirring in between the readings. My thought was that I would stop the mash as soon as I hit my target preboil gravity and then pull the bag. A sort of "brew to numbers" as opposed to "brew to time" like I did with my 3V system. (Now my brew sheets are all full of tables of numbers!)

After about five brews of doing this I started noticing a pattern. At about the 30 min mark I am getting to about "90% conversion" Meaning, about 90% of the way to my preboil gravity. Then, little to no noticeable change occurs until about the 45-50 min mark. This pattern has held true for 16 brews now and stirring has no noticeable effect on the numbers (as I have experimented along the way.) I then see a jump in my gravity again and typically achieve the gravity I look for w/in 60 minutes.

It's been interesting to chart the numbers because it gives me a better picture as to what is going on during the mash. And, it gives me something to do while I'm mashing.

 

[doug293cz]

I'm having trouble conceptualizing why concentration gradients would develop. They are recirculating after all.

It depends on how uniform the flow pattern of the recirculation is, and to a little extent on just how much shear there is due to the flow. If there is any channeling in the flow pattern, then gradients will develop. If the flow is too slow in the grain bed, then there will not be enough shear to disrupt the gradients that develop naturally.

Ideally, the recirc would provide good mixing in the grain bed, and then stirring wouldn't make any difference. But I don't know if that is the case or not for @hafmpty 's system.

Brew on

 

[doug293cz]

This thread has gotten a little off-topic but I thought I'd chime in again as well.

Since I started BIAB with my RIMS tube I have been taking readings during my mash.

I take readings with my refractometer at 5 minute intervals and stirring in between the readings. My thought was that I would stop the mash as soon as I hit my target preboil gravity and then pull the bag. A sort of "brew to numbers" as opposed to "brew to time" like I did with my 3V system. (Now my brew sheets are all full of tables of numbers!)

After about five brews of doing this I started noticing a pattern. At about the 30 min mark I am getting to about "90% conversion" Meaning, about 90% of the way to my preboil gravity. Then, little to no noticeable change occurs until about the 45-50 min mark. This pattern has held true for 16 brews now and stirring has no noticeable effect on the numbers (as I have experimented along the way.) I then see a jump in my gravity again and typically achieve the gravity I look for w/in 60 minutes.

It's been interesting to chart the numbers because it gives me a better picture as to what is going on during the mash. And, it gives me something to do while I'm mashing.

This is really interesting! I have read that the starch particle size distribution is bimodal (two peaks in the size vs number curve), and that the small starch particles are more difficult to gelatinize (I don't know why.) So, what you are observing could be due to much longer times to gelatinize the particles at the small end of the distribution. Starch to sugar conversion cannot happen until the starch has gelatinized.

Brew on

 

[thekraken]

This thread has gotten a little off-topic but I thought I'd chime in again as well.

Since I started BIAB with my RIMS tube I have been taking readings during my mash.

I take readings with my refractometer at 5 minute intervals and stirring in between the readings. My thought was that I would stop the mash as soon as I hit my target preboil gravity and then pull the bag. A sort of "brew to numbers" as opposed to "brew to time" like I did with my 3V system. (Now my brew sheets are all full of tables of numbers!)

After about five brews of doing this I started noticing a pattern. At about the 30 min mark I am getting to about "90% conversion" Meaning, about 90% of the way to my preboil gravity. Then, little to no noticeable change occurs until about the 45-50 min mark. This pattern has held true for 16 brews now and stirring has no noticeable effect on the numbers (as I have experimented along the way.) I then see a jump in my gravity again and typically achieve the gravity I look for w/in 60 minutes.

It's been interesting to chart the numbers because it gives me a better picture as to what is going on during the mash. And, it gives me something to do while I'm mashing.

Very interesting. You said charts, can you share the data, or graphs? We love graphs!