Mill Gap for BIAB (Efficiency Problems)

[Epos7]

I'm starting to wonder if my stainless steel kettle might be leaching some metal ions into my brewing water that are interfering with the starch conversion process.

Last time I brewed I noticed that after my RO water had been sitting in the kettle for a little while, TDS levels went through the roof. I thought I had cleaned the kettle pretty well, but wasn't ready to rule out some stubborn residue causing the increase.

After that last batch, I decided to conduct an experiment. I cleaned the kettle with soap and water, rinsed, did a PBW soak, scrubbed some more, and rinsed thoroughly with a high pressure hose. I also cleaned out all the fittings. I'm positive it was 100% clean. I then filled it with five gallons of reverse osmosis water. My TDS meter read 3ppm after the kettle had collected five gallons of RO water, a process that takes several hours with my filter. I then left the kettle with the lid on for a little under two days, and checked it again this morning. It now reads 320ppm.

I don't know if it's possible for metal ions to interfere with the starch conversion process, but I know something is leaching into my water.

 

[Epos7]

If it is iron leaching into my brewing water from my kettle, it could explain my poor conversion efficiency:

http://www.mbaa.com/meetings/distri...ingPresentationBrewingRawMaterialsQuality.pdf

Iron levels should be low to avoid incomplete saccharification

 

[wilserbrewer]

I'm starting to wonder if my stainless steel kettle might be leaching some metal ions into my brewing water ....

I wouldn't have thought that possible, but I will curiously wait for someone more knowledgeable to comment.

 

[dmtaylor]

Wow, this is indeed unexpected. I'm not smart enough to answer this one either.

 

[Epos7]

I may have spoken too soon. While I have been able to reproduce the 300+ ppm measurements of the RO water stored for several days in my kettle, I've also started getting readings in the 5-10ppm range, which is what I would expect for RO water. At this point I think it's likely the high readings I am seeing are instrumentation error, and I don't have excess iron or anything in my brewing water. That points to mill gap as still being the culprit for my poor efficiency.

 

[cegan09]

I'm not saying that gap isn't an issue, however I somewhat fixed my poor numbers by rinsing the grains after pulling the bag. I have missed every OG number on every brew day so far, and have some bad numbers. Crush is good, I stir like mad, stir several times during mash, squeeze the crap out of the bag, etc. Still miss.

Last brew I took a 5 gallon bucket, drilled a ton of holes in the bottom, then set that into my 6.5gallon bottling bucket. Pulled the bag at the end of the mash, drained, squeezed some, then put the bag into this bucket setup. I then poured a gallon of clean water over the grains using a pasta strainer to help "spread" it. Water was at mash temp. I made sure i had this recorded in beer smith to make sure my volumes were right. I then squeezed the crap out of the bag again and drained this extra gallon into the kettle. I nailed my numbers that brew. This may be something to consider. I know many people claim they don't need any type of sparge or rinse, but I couldn't get there. Might be worth considering if messing with the gap doesn't gain you anything.

 

[wilserbrewer]

Wheat and rye are hard little berries, crush more!

Some actually keep a corona mill for dedicated wheat and rye milling.

 

[dmtaylor]

I'm not saying that gap isn't an issue, however I somewhat fixed my poor numbers by rinsing the grains after pulling the bag.... poured a gallon of clean water over the grains using a pasta strainer to help "spread" it. Water was at mash temp. I made sure i had this recorded in beer smith to make sure my volumes were right. I then squeezed the crap out of the bag again and drained this extra gallon into the kettle. I nailed my numbers that brew. This may be something to consider. I know many people claim they don't need any type of sparge or rinse, but I couldn't get there. Might be worth considering if messing with the gap doesn't gain you anything.

Yep, sparging will help, especially as your desired gravity approaches 1.060-1.065 or beyond. Above that point, it's really difficult to achieve decent efficiency without a sparge -- I don't care how hard you squeeze. I don't squeeze at all ever. I just sparge. It's quick and easy and very effective.

 

[Epos7]

After giving it some more thought, I've concluded that there are likely four variables that affect the final crush: roller diameter, mill gap, roller type (knurled or helical slotted), and roller speed.

With my mill set at 0.035" my drill is working pretty hard, and thus not spinning all that fast. I'm hypothesizing that a slower mill speed may be more likely to crush the grains, and a higher mill speed may be more likely to tear them. When taking the other variables into account, especially the difference between knurled and helical rollers, it seems likely that a 0.035" gap on one mill produces a significantly different crush than a 0.035" gap on another mill.

With this is mind, I think for my next batch I'll try setting the gap to 0.025" and see if my drill can handle it. If not I'll try 0.030". In the future I intend to purchase a direct drive motor to power the mill, which should help by maintaining a consistent roller speed. I'm working on designing a small table to accommodate this at the moment. Until then I'll try a narrower gap with my drill and see where that gets me. If I don't start to see some significant improvements, I'll look into adding a sparge step.

 

[wilserbrewer]

After giving it some more thought,.

Stop thinking and crush more lol, just kidding. I would try and hold .025 even if it means narrowing the mill feed even temporarily with a little duct tape.....

Perhaps all barley malt, no wheat as well.....

cheers!

 

[Epos7]

Stop thinking and crush more lol, just kidding. I would try and hold .025 even if it means narrowing the mill feed even temporarily with a little duct tape.....

Perhaps all barley malt, no wheat as well.....

cheers!

Ha! I would like to, but I've got to wait a couple weeks for some space to open up in my fermentation chamber. That leaves me a lot of time to ruminate, maybe too much

 

[gezzanet]

my mill is set to 0.035" single pass and i get 78% brewhouse eff. I dont stir at all after mash in. Mash in is the only time I stir. I havent seen any change in efficiency by not stirring. I have been trying this as there was a school of thought that very very slow lifting of the bag after mash helped reduce the amount of flour and trub in the kettle. I let it hang over the kettle for the 30 min it takes my system to reach boil and I also squeeze just before i move it.
i havent sparged because i dont think i need to but then again most of my brews are below 1.060 so cant comment on need to sparge higher OG

 

[wilserbrewer]

That leaves me a lot of time to ruminate, maybe too much

Ok than read this about crushing grain....note the "expert" didn't even use a feeler gauge but rather just by eye...Look at pics of what a good crush looks like, I believe it to be more crushed than where you are.

http://brewlikeapro.net/maltmilling.html

 

[gezzanet]

On another note when i set my mill i used a feeler gauge and noticed that there is a slight misalignment in the rollers com,pared to the adjustment markers on the mill ends. If I used the adjustment marks on the sides of the mill and set them the same the feeler gauge at one roller end is not the same as the other. I now ignore the markings if i move it and set using feeler gauges at each end of the mill rolls.

 

[Epos7]

Ok than read this about crushing grain....note the "expert" didn't even use a feeler gauge but rather just by eye...Look at pics of what a good crush looks like, I believe it to be more crushed than where you are.

http://brewlikeapro.net/maltmilling.html

Wow, what a great article, and an excellent method for quantifying mill setup. I would say my crush falls in between his examples of "good" and "bad" meaning I can afford to tighten it up some more.

 

[Epos7]

On another note when i set my mill i used a feeler gauge and noticed that there is a slight misalignment in the rollers com,pared to the adjustment markers on the mill ends. If I used the adjustment marks on the sides of the mill and set them the same the feeler gauge at one roller end is not the same as the other. I now ignore the markings if i move it and set using feeler gauges at each end of the mill rolls.

I noticed the same with my mill, and also elected to set it using the feeler gauge and ignore the position of the adjustment knob.

 

[wilserbrewer]

Wow, what a great article, and an excellent method for quantifying mill setup.

I believe he mentions wheat and rye as well....

Also notice the impressive numbers that the cheap $25 corona mill puts out lol, I just find that interesting / ironic.

 

[BeardedBrews]

There isn't really a reason you'd have to wait for a new batch to test your conversion efficiency. 2# of 2-row and a gallon of hot water are cheap, you can just dump it when you're done.

For what it's worth, I keep my Cereal Killer between the 0.025 and 0.050 marks on the side and get fairly good conversion efficiency, but I also found early on that I was putting volume numbers into Brewer's Friend "wrong" based on my BIAB approach.

"Mash Complete" Step - Enter the total strike water volume
"Pre-Boil Gravity" Step - Enter the volume after you've squeezed the grain bag
"Boil Complete" Step - Volume in the kettle after you chill it but before transferring
"Brew Day Complete" Step - Volume in the carboy

Using this approach means that each step can only have one source of "loss".

Mash - Conversion Efficiency
Pre-Boil - Lautering Losses
Boil Complete - N/A
Brew Day Complete - Transfer and Trub Losses (and any losses because it wouldn't fit in the carboy)

http://cdn.brewersfriend.com/understanding_efficiency_large.png

I included a snapshot of the brew I did Sunday morning. It was a 20 minute mash / 20 minute boil which meant my conversion efficiency wasn't great (88%), and I overshot my final volume which ended up being the biggest hit on my brew-house (BH 66%).


For my process the biggest things that have helped improve my conversion efficiency were:

1. Mind the Gap - I am more consistent with my home mill, and I keep it relatively tight.
2. Stir the Mash - Unless it's a short mash I stir every 15 minutes during the mash. It has helped out considerably.

I honestly worry less about brew-house efficiency numbers because they swing so much depending on how much trub and hops you send into the carboy. Brewer's Friend lets you pick the ending kettle volume instead of the carboy volume as your batch size target which normalizes your efficiency a bit.

 

[Epos7]

There isn't really a reason you'd have to wait for a new batch to test your conversion efficiency. 2# of 2-row and a gallon of hot water are cheap, you can just dump it when you're done.

Fair point, and thanks for the post. It looks like I've been using a different tool than you have on Brewer's Friend. I've just been using the Brewhouse Efficiency Calculator.

 

[brew703]

I'm not saying that gap isn't an issue, however I somewhat fixed my poor numbers by rinsing the grains after pulling the bag. I have missed every OG number on every brew day so far, and have some bad numbers. Crush is good, I stir like mad, stir several times during mash, squeeze the crap out of the bag, etc. Still miss.

Last brew I took a 5 gallon bucket, drilled a ton of holes in the bottom, then set that into my 6.5gallon bottling bucket. Pulled the bag at the end of the mash, drained, squeezed some, then put the bag into this bucket setup. I then poured a gallon of clean water over the grains using a pasta strainer to help "spread" it. Water was at mash temp. I made sure i had this recorded in beer smith to make sure my volumes were right. I then squeezed the crap out of the bag again and drained this extra gallon into the kettle. I nailed my numbers that brew. This may be something to consider. I know many people claim they don't need any type of sparge or rinse, but I couldn't get there. Might be worth considering if messing with the gap doesn't gain you anything.

Did you withhold a gallon of water from your strike water volume to pour over your grains? I don't sparge but I normally just dunk the bag in and out of the wort then squeeze using some bbq gloves to squeeze all the wort out. My brewhouse efficiency always sucks, usually under 70%. I like the idea of using a bucket and drilling holes in the bottom and may try that on my next brew to see if that improves my efficiency.

 

[cegan09]

Did you withhold a gallon of water from your strike water volume to pour over your grains? I don't sparge but I normally just dunk the bag in and out of the wort then squeeze using some bbq gloves to squeeze all the wort out. My brewhouse efficiency always sucks, usually under 70%. I like the idea of using a bucket and drilling holes in the bottom and may try that on my next brew to see if that improves my efficiency.

Yes. In Beer Smith I specify whatever volume I'll rinse with as "kettle top up" so it pulls that from the strike volume and adjusts strike temps correctly. You can do the same thing without messing with the software just by holding off on a gallon.

 

[BeardedBrews]

Fair point, and thanks for the post. It looks like I've been using a different tool than you have on Brewer's Friend. I've just been using the Brewhouse Efficiency Calculator.

I'm using the brew session log function to track my brews, it makes it easier for me to keep all the data in one place, although it also means I have to keep a phone or ipad nearby during the brew day.

 

[Epos7]

I've set my mill to 0.025". I looks like 0.022" is as low as I can go, so hopefully 0.025" gets close to a good result. I could try mashing a couple pounds of 2-row in a gallon of water, but maintaining mash temps on that small of a volume would be challenging. I've got a friend who is going to brew soon and wants to use my mill. I'm hoping he can be my tester.

 

[doug293cz]

I've set my mill to 0.025". I looks like 0.022" is as low as I can go, so hopefully 0.025" gets close to a good result. I could try mashing a couple pounds of 2-row in a gallon of water, but maintaining mash temps on that small of a volume would be challenging. I've got a friend who is going to brew soon and wants to use my mill. I'm hoping he can be my tester.

Do the test mash in a pot you can put in your oven. Will help hold temperatures.

Brew on

 

[pricelessbrewing]

Do the test mash in a Thermos.

 

[Epos7]

I brewed again today, and with a 0.025" gap I hit 86% conversion efficiency. I think next I'll try going to 0.022", which is as low as my mill can go. 86% is a significant jump from where I was. For this brew I also fired up the burner for five minutes about 15 minutes into the mash to bring it back to 152 as it had already dropped a few degrees. This might also have aided efficiency.

 

[ch19]

I brewed again today, and with a 0.025" gap I hit 86% conversion efficiency ... 86% is a significant jump from where I was.

Great job!

 

[Epos7]

Entered the numbers wrong, conversion efficiency was 82% not 86%. I'm wondering how much of that improvement was from the finer crush and how much was from reheating the mash water. Think I'll go as low as my mill can go next time - .022" and see what happens. If that doesn't get me up to 90% there's not much else I can do. Still, at least I'm moving in the right direction.

 

[Epos7]

I emailed Monster Brewing and got some good info. They said the gap setting for the helical rollers is much different than for knurled rollers, and recommended starting at 0.030" and going down from there. It's good to know the setup is different, and I'm hoping I can take another big jump in conversion efficiency going down to the lowest setting 0.022".

 

[normonster]

I emailed Monster Brewing and got some good info. They said the gap setting for the helical rollers is much different than for knurled rollers, and recommended starting at 0.030" and going down from there. It's good to know the setup is different, and I'm hoping I can take another big jump in conversion efficiency going down to the lowest setting 0.022".

After that you should borrow a Corona and grind it up even further and check the diff. When I was dogging on Corona mills everyone kept saying how they're awesome for BIAB. It sure would be a bitch though if you got better results with a $50 mill vs. your Monster.