It's a little strange that the Monster can't go lower than 0.022" as it says it can go down to 0 on their website. Still, if I can get good results I'll be happy. I mostly bought the Monster Mill because it should last forever. I'm pretty confident the rest of my process is sound, but I'm still pretty new to this and it's certainly possible I'm overlooking something obvious that is hurting my conversion efficiency.
Mill Gap for BIAB (Efficiency Problems)
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It's a little strange that the Monster can't go lower than 0.022" as it says it can go down to 0 on their website. Still, if I can get good results I'll be happy. I mostly bought the Monster Mill because it should last forever. I'm pretty confident the rest of my process is sound, but I'm still pretty new to this and it's certainly possible I'm overlooking something obvious that is hurting my conversion efficiency.
normonster
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I have the MM2 (I think it is) and it looks like it goes to 0.
One tip that helped me that may or may not help you is this: when you set the gap, make sure the roller is on it's way closed when you tighten the thumb screws, as opposed to on it's way wide open.
Mine slipped a little on the first batch I used it with and when I called concerned that the thumbscrews weren't locking it down right they told me that and it hasn't slipped since.
I had the same thought as you and basically set the gap by rotating the rollers to find the smallest possible distance. The 2" mills hold their settings a little differently than the 1.5" mills, and it seems to be pretty solid.
Monster said they did some sieve testing around 0.025" gap on the mill I have, and found 63% of the grist in the coarse pan, with 9% flour in the bottom pan. Based on the link posted earlier in this thread by wilserbrewer, that's pretty close to an ideal crush, but could be adjusted to bring the coarse pan down below 60%. I'm hoping dropping the gap to 0.022" will do just that, although I'll have no way of testing.
Couple of questions just to clarify -
It looks like you are taking a gravity reading to measure your conversion efficiency after you have squeezed the bag and taken any additional sparge steps, is that right? I've been taking a reading before squeezing the bag, which is probably making my mash/conversion efficiency appear lower than it is. Any sugars left in the bag represent starches that have already been converted to sugars and should therefore be included in the conversion efficiency. It's a little confusing applying these measurements to BIAB, but I think I have my head wrapped around it now.
Mash efficiency = conversion efficiency, if I'm understanding correctly. For example, I just brewed a batch with a friend on his system, using my mill. We set the mill gap to 0.022". His grain bill was 32lbs 2 Row and 2lbs Munich, and we mashed in 16 gallons of water.
That grain bill gives a total of 1222 points / 16 gallons = 76.375 points per gallon, or a potential gravity at 100% efficiency of 1.076.
Our refractometer reading after squeezing the bag was 14 brix, or a gravity of 1.0568 (56.8 points).
56.8 points / 76.375 points gives us a mash efficiency of ~74%.
Now you're confusing me. Here's my understanding, based on science (FYI, I have an engineering degree):
Squeezing the bag will help your overall brewhouse efficiency, but this overall improvement is due to lauter efficiency, not conversion efficiency. Conversion has to do with starches turning into sugars. Conversion does not improve from squeezing the bag; the conversion efficiency is a measurement of the effectiveness of a chemical reaction which is affected by crush, enzymatic content, temperature, time, pH, etc. You can't just squeeze a starch to turn it into sugar. The concentration of sugars is the same both inside and outside of the grain bag. In other words...
After the mash is complete, any specific gravity readings taken before and/or after squeezing the bag should be identical. However, after squeezing the bag, even though the concentration stays the same, you will indeed have more total mass of sugar collected -- this sugar is not wasted by being soaked up into the spent grains. This extraction of total sugar describes lauter efficiency, which is more based on physical separation than the chemical reaction. You can subsequently concentrate the sugars down in the boil as much or as little as you want, as the total amount of sugar stays the same, while evaporation only affects the water content / volume.
Maybe I'm just rambling, I don't know. I'm trying to make sure you don't think you'll get different readings before and after squeezing a bag, because you won't -- concentration stays the same before and after. However the boil will definitely change the concentration, and so will the mash... at least, for the first 30 minutes or so until conversion nears completion.
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"Mash efficiency" ("Pre-Boil Efficiency" in BrewersFriend's terminology) is made up of two components: "Conversion Efficiency" - the percentage of starch in the grain converted to sugar during the mash, and "Lauter Efficiency" - the percentage of the sugar actually created in the mash that makes it into the boil kettle.
Mash Efficiency = Conversion Efficiency * Lauter Efficiency
Conversion efficiency can be as high as 100%, meaning you converted all of the available starch. Lauter efficiency is alway less than 100% because of the sugar content of the wort remaining in the wet grain.It turns out in practice that for typical grain bills, the maximum potential wort SG in the mash, at 100% conversion efficiency, depends only on the water to grain ratio in the mash (ref: http://braukaiser.com/wiki/index.php?title=Understanding_Efficiency#Measuring_conversion_efficiency.) So, conversion efficiency can be measured by measuring the SG of the wort in the mash, and then dividing the measured value by the maximum possible for the water/grain ratio used. A table of maximum SG's is provided in the reference linked above.
Since you mashed 34 lbs of grain in 64 qts (16 gal) of water, your water/grain ratio was 64 qt / 34 lb = 1.88 qt/lb. From the reference, your maximum possible wort SG was about 1.067. Since your measured SG was 1.0568, your conversion efficiency was:
56.8 / 67 = 0.8478 = ~85%
This is not a very good conversion efficiency.Your potential max SG calculation is in error because the PPG is defined by wort volume not water volume. The wort volume is higher than the water volume due to the volume added by the dissolved sugar. For 16 gal of strike water with 34 lbs of grain @ 100% conversion efficiency, the actual volume of wort in the mash would be 17.785 gal. So, the sugars make up 1.785 gal of the wort volume.
Brew on
BeardedBrews
Well-Known Member
Whew, I waited long enough for Doug to take care of the math. That was a close one!
All I can add is that it seems much easier to get good consistent beer by adjusting the consistency, quality, and quantity of raw materials instead of adjusting your entire brewing process.
Thanks for taking the time to respond.
Agreed.
It's not though. At least not in my experience. Brewing this batch with my friend we did a little experiment.
First we measured the wort at the end of the 60 minute mash: 9.25 brix
Next we squeezed the bag into the kettle and took another wort sample: 14.0 brix
Finally we squeezed some of the wort remaining in the bag into a sample cup and measured that: 25.0 brix
Clearly the wort left in the bag has a higher concentration of sugars than the wort in the kettle. Those sugars have already been converted from starch - squeezing the bag isn't converting anything, but it is adding more of the sugars you converted to your kettle (and at a higher concentration than the sugars already in the kettle). Since those sugars have already been converted, my contention is that squeezing the bag should be included in calculating conversion efficiency.
I have also observed the brix/gravity of my wort rising after I have squeezed the bag on my previous brews.
Agreed.
It's not though. At least not in my experience. Brewing this batch with my friend we did a little experiment.
First we measured the wort at the end of the 60 minute mash: 9.25 brix
Next we squeezed the bag into the kettle and took another wort sample: 14.0 brix
Finally we squeezed some of the wort remaining in the bag into a sample cup and measured that: 25.0 brix
Clearly the wort left in the bag has a higher concentration of sugars than the wort in the kettle. Those sugars have already been converted from starch - squeezing the bag isn't converting anything, but it is adding more of the sugars you converted to your kettle (and at a higher concentration than the sugars already in the kettle). Since those sugars have already been converted, my contention is that squeezing the bag should be included in calculating conversion efficiency.
I have also observed the brix/gravity of my wort rising after I have squeezed the bag on my previous brews.
Since you mashed 34 lbs of grain in 64 qts (16 gal) of water, your water/grain ratio was 64 qt / 34 lb = 1.88 qt/lb. From the reference, your maximum possible wort SG was about 1.067. Since your measured SG was 1.0568, your conversion efficiency was:56.8 / 67 = 0.8478 = ~85%This is not a very good conversion efficiency.
Your potential max SG calculation is in error because the PPG is defined by wort volume not water volume. The wort volume is higher than the water volume due to the volume added by the dissolved sugar. For 16 gal of strike water with 34 lbs of grain @ 100% conversion efficiency, the actual volume of wort in the mash would be 17.785 gal. So, the sugars make up 1.785 gal of the wort volume.
Brew on
I am finding a lot of conflicting information on what constitutes good or typical conversion efficiency. Some say 95% or higher should be easily attainable, others such as BeerSmith say typical mash efficiency is in the 80% range:
http://beersmith.com/blog/2014/11/0...vs-mash-efficiency-in-all-grain-beer-brewing/
I lean toward believing what you and the Braukaiser wiki you linked to say, which is that something around 95% should be easy to attain. Given that I'm way off, I'd like to figure out what I'm doing wrong, but that's proving very difficult
Aha, that makes sense. So to sidetrack a little bit, how is grain absorption determined?
Is it [strike water volume] - [pre-boil volume]
or
[strike water volume] - [pre-boil volume] - [volume of sugars dissolved into mash]
It seems like most are just using the first formula, but that's not really taking into account the sugars added back into the wort, which is dependent on conversion efficiency. If the second formula is correct, then grain absorption is also dependent to a small degree on conversion efficiency.
1MadScientist
Well-Known Member
Isn't a 14 brix equal to a 1.0592
I used the Brewer's Friend calculator, it spits out 1.0568.
1MadScientist
Well-Known Member
Sorry, I was thinking of a Brix hydrometer.
Wow. This seems scientifically improbable to me. The only explanation that I can think of is that you're not stirring the mash enough to force the concentration to be equal everywhere, AND there is still some active conversion going on inside the grains. If conversion is still happening then yes I would expect a lot more sugars in the grains, but if it is complete or very near complete then I would expect very little difference in concentration -- maybe a couple points Brix if conversion is like 90% or so complete but not a huge difference like you're seeing. Besides stirring to even out the concentration, this also makes me wonder if the crush is inadequate. If it's not then you essentially have millions of starchy "sponges" holding sugars that can't get out into the liquid portion of the mash, and even with a lot of stirring and even squeezing you can't get the majority of it out.
Bottom line from what I can tell is that if you crush very well and stir very well, then the concentrations should be the same inside and out. If you're not seeing that, then improvements are needed in the crush and or the stirring.
I'm crushing at 0.022" which is as low as my mill can go. The crush looks pretty good to me, but I'll post a picture when I brew again this weekend.
My process it to stir for 2 minutes at the start of the mash and break up any dough balls, then stir at 15 minute intervals for 30-60 seconds until the mash is complete. I'll definitely try stirring more next time, although there is a balancing act between how long I stir for and how much heat I lose from my mash tun as it's un-insulated when I'm stirring.
Based on my theoretical discussion above, the only time we really should ensure we stir well is at the very end of the mash right before pulling the bag, or maybe 3-5 minutes before pulling the bag. Doing that should make a big difference. I'll have to ensure I do this from now on as well -- maybe I learned something from this thought-experiment!
1MadScientist
Well-Known Member
Could you share your recipe with us before you brew? The total grain bill weight, target OG, batch size, starting water, etc. etc. With an efficiency problem and a refractometer handy, why don't you monitor readings past the 60 mins. mash and go out to 90 mins. + ?. What size kettle do you have? Can you do a full volume mash?
A SG measurement right before and after pulling the bag at the end of the mash could be a useful indicator for whether the mash has been stirred well enough. I think next time around I'll try dunking the bag a few times at the end of the mash as well. Most of my stirring has been at the beginning of the mash, maybe stirring at the end is all I need to do!
Pretty much my thoughts as well. Saved me some typing
OP's estimated conversion efficiency was only 85%, so I think the continued conversion during the post-initial drain steps is definitely playing a role. Concentration gradients at the grit surfaces is also likely to be in play.
Agree, a good stir prior to pulling the bag is essential.
Brew on
I'm going to try brewing Brulosophy's Munich Helles recipe.
Total grain bill: 9.375 lbs
8.125 lbs Belgian Pilsner
1.125 lbs Munich Light
0.125 lbs Melanoidin
- Target OG: 1.047
- Total mash water: 9 gallons
- Strike temp 155F
- 60 minute mash at 150F
- Est pre-boil volume: 8.41 gallons
- 90 minute boil
- Shooting for 5.25 gallons into the fermenter
I have a 15 gallon kettle and have been doing a full volume mash for every batch so far. Depending on how my SG looks at the end of 60 minutes, I may prolong the mash and see what happens. That's a good thought.
What about taking gravity readings at 30 minutes then at 45 to look for a change? I've read how some feel they can get away with only a 30 minute mash. If you see the gravity increasing from 30 to 45 to 60 then you can keep going longer. If it stays the same wouldn't that be an indication you can stop? I'm facing similar issues and I'd hate to go to a 90 minute mash if I don't need to do I might try to take more readings during the mash.
I've actually done this on most of the brews I've completed so far, and I do see the gravity increasing throughout the mash. For example, my last mash:
15 minutes: 1.018
30 minutes: 1.040
45 minutes: 1.041
60 minutes: 1.043
It does seem to slow down toward the end, which is why I'm hoping I can keep doing a 60 minute mash but stir better at the end and dunk the bag a couple of times to better rinse it. Like you I don't want to do a 90 minute mash if I don't have to.
Yep, taking readings of mash SG will tell you how far your conversion has progressed. You should stir well before each reading for the same reason you stir before pulling the bag. Compare your measured SG with the value in the table here to determine what your conversion efficiency is at that point in the mash. You can end the mash when your conversion efficiency gets close enough to 100% to satisfy you. If you get to a point where the SG no longer is increasing, even if significantly less than 100% conversion, your enzymes have probably completely denatured, and you are done (whether you want to be or not,)
As said above, if the gravity is still increasing between measurements, you mash is not "done." Again, use the link above to determine the actual % conversion.
Dunking the bag will not provide any benefit over just stirring adequately, unless you dunk in fresh water (then you are doing a dunk sparge, which is a version of a batch sparge.)
Brew on
Well maybe a longer mash is called for then. When I brew this weekend I'll try mashing out to 90 minutes and monitor the SG. Kind of kills some of the time savings of BIAB, but if it helps me attain better conversion efficiency then it's worth it.
Required mash time for full conversion is primarily determined by crush. Gelatinization of the starch is the rate limiting step in the conversion process. The enzymes cannot do their work until the starch is gelatinized (and they work even faster once the starch is dissolved in the wort.) Gelatinization proceeds from the surface of the grits towards the center. The larger the grit, the greater the distance from the surface to the center, and the longer it takes the grit to fully gelatinize.
If you can't reduce the crush size, you may have to accept longer mash times or lower conversion efficiency.
Brew on
If you can't reduce the crush size, you may have to accept longer mash times or lower conversion efficiency.
Brew on
Required mash time for full conversion is primarily determined by crush. Gelatinization of the starch is the rate limiting step in the conversion process. The enzymes cannot do their work until the starch is gelatinized (and they work even faster once the starch is dissolved in the wort.) Gelatinization proceeds from the surface of the grits towards the center. The larger the grit, the greater the distance from the surface to the center, and the longer it takes the grit to fully gelatinize.
If you can't reduce the crush size, you may have to accept longer mash times or lower conversion efficiency.
Brew on
Exactly. What he said.
Required mash time for full conversion is primarily determined by crush. Gelatinization of the starch is the rate limiting step in the conversion process. The enzymes cannot do their work until the starch is gelatinized (and they work even faster once the starch is dissolved in the wort.) Gelatinization proceeds from the surface of the grits towards the center. The larger the grit, the greater the distance from the surface to the center, and the longer it takes the grit to fully gelatinize.
If you can't reduce the crush size, you may have to accept longer mash times or lower conversion efficiency.
Brew on
That makes perfect sense, however I'm crushing finer than most, and seeing significantly lower conversion efficiency than most. Based on the sieve testing Monster Brewing performed, and the gap I have my mill set to, I should have really good crush. To my inexperienced eyes it looks really good, but I'll post a picture later this week when I get ready to brew my next batch.
It seems like non-BIAB brewers, who have to use a coarser crush, are seeing pretty good conversion efficiency too, and other than the presence of the bag, the mash is identical.
The only other thing I can think of is to machine new bulkheads for my Monster Mill that would allow me to adjust the mill gap even finer. I could do this, it would take some work, and seems well outside the realm of what should be necessary.
I'm stumped. Will try stirring like a madman this weekend as well as extending the mash and see how things go. Otherwise I'll likely just assume 80-85% conversion efficiency moving forward. The fact that I'm getting lower conversion efficiency than I should will forever bug me, however.
I appreciate all the input. While I may not have completely solved my problem, I've seen some improvement and I've learned a lot more along the way.
wilserbrewer
BIAB Expert Tailor
Just a guess here, I'm thinking the helical slotted rollers may not free the inside of the kernel, and the kernel remains whole with the husk cracked, but not free of the kernel. This would slow conversion. The quest for husk preservation may have been taken too not allowing easy access to the inner starch portions ... idk.
Monster claims this is a first in homebrewing mills....perhaps this concept is in the developmental stages for smaller 2 roller mills.
Perhaps it works great on larger multi roller commercial mills but doesn't scale down quite so simply.
Anyways I have a hunch at the reduced gap your planning, and THOROUGH stirring, your efficiency will jump.
Milling new end plates?
OMG I would look to send it back to MM before taking on that project.
All the best!
Wilser
Monster claims this is a first in homebrewing mills....perhaps this concept is in the developmental stages for smaller 2 roller mills.
Perhaps it works great on larger multi roller commercial mills but doesn't scale down quite so simply.
Anyways I have a hunch at the reduced gap your planning, and THOROUGH stirring, your efficiency will jump.
Milling new end plates?
OMG I would look to send it back to MM before taking on that project.
All the best!
Wilser
Very interesting theory! There is obviously something going on as Monster says the mill gap setting is different than with a knurled roller. The depth of the helical cuts in the roller is substantial, so if two of the cuts were to align around a grain, the mill gap is significantly greater than if the non-cut portions of the rollers line up.
This is also possible, and I'd be a little frustrated to have spent such a large sum of money on a prototype. Monster has been a great source of information however, and their sieve testing gives me confidence that the mill *should* produce a very good grain crush. At a mill gap ~0.025" they obtained 63% of the grist in the coarse pan, which is close but not quite in the ideal range referenced in the link you posted earlier in the thread. My hope is that setting the mill to its lowest setting of 0.022" will get me there.
I already tested the reduced (smallest possible) gap on the batch I brewed with a friend, and our conversion efficiency wasn't great. That was with his process though, which doesn't involve as much stirring as mine. I've yet to try the finest gap setting with my process, so I'll reserve judgement until this weekend. I do hope you're right
As helpful as Monster Brewing has been in providing information to dial in the grain crush, they weren't willing to concede that the mill might require a finer setting than the supplied bulkheads will allow, so I'm not sure I'd get very far in requesting a return.
I've also invested a significant amount of time already in milling a base for the mill out of a block of aluminum (see attached image of almost complete base prior to filleting). On top of that I've designed a table for the mill to accommodate a direct-drive motor, construction of which is almost complete.
Thanks again, really appreciate all the input I've received here!
1MadScientist
Well-Known Member
Thanks for sharing in advance of your next brew day.
Your 9 gallons starting water is spot on, that's good.:rockin:
1.047 OG with 9# grains
34.68 L = 9.16 Gal of cold starting water
33.57 L = 8.87 Gal of boiled hot wort
32.27 L (adjusted) pre-boil to a cold temperature
34.68 L - 32.27 L = 2.41 L (difference)
9 lbs grain = 4.083 kg
4.083 kg * 0.6 L/KG (hot liquor retained by grain) = 2.45 L
Apparent grain absorption = 2.45 L / .647 Gal
pre-boil 8.87 gals @ 1.0326
evaporation in 90 mins. 2.71 gals
flame-out 6.16 gals
cooled at 5.92 gals @ 1.047
trub 0.64 gals
in fermentor 5.28 gals.
I will always recommend a 90 mins mash with enough stirring plus keeping the bag in the kettle during heating to a mashout (takes about 10+ mins to get to mashout temp) , one last stir, then lift the bag.
Good Luck
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