Mill Gap for BIAB (Efficiency Problems)

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I've ordered a 0-12 brix hydrometer, should have it next week to do some more testing. It has 0.1 brix graduations, which should give me a pretty accurate picture.
 
I'm perfectly happy with the standard models of hydrometer and refractometer. Two significant digits is plenty accurate enough, whether you're talking about ABV (5.03% vs. 5.04%, who cares!), specific gravity (1.0513 vs. 1.0514, I don't care!), etc. The average homebrewer thinking that they can measure anything good to 3 sig figs in a non-laboratory setting is very likely just fooling himself/herself, as there's probably dozens of variables and margins for error all going on at one time and it's hard to come up with all of them. Even a slight draft of air, or humidity, or a few degrees temperature difference between instrument and the thing being measured can sometimes mess things up. Alcohol also (if present) quickly evaporates and I know for a fact can royally mess up any final gravity readings with a refractometer.

But anyway... :)
 
dmtaylor said:
I'm perfectly happy with the standard models of hydrometer and refractometer. Two significant digits is plenty accurate enough, whether you're talking about ABV (5.03% vs. 5.04%, who cares!), specific gravity (1.0513 vs. 1.0514, I don't care!), etc. The average homebrewer thinking that they can measure anything good to 3 sig figs in a non-laboratory setting is very likely just fooling himself/herself, as there's probably dozens of variables and margins for error all going on at one time and it's hard to come up with all of them. Even a slight draft of air, or humidity, or a few degrees temperature difference between instrument and the thing being measured can sometimes mess things up. Alcohol also (if present) quickly evaporates and I know for a fact can royally mess up any final gravity readings with a refractometer.

But anyway... :)
Click to expand...

I work in a laboratory, and previously worked in a wine laboratory, so I guess I have that going for me :) Of course, I don't do my homebrew stuff there. At the winery we had digital density meters - now those are cool.

The standard hydrometer is fine for checking the gravity of your wort, but if you want to take advantage of the convenience of a refractometer and need to determine its wort correction factor, a standard range hydrometer isn't going to give you the resolution to do that. At least in my experience :mug:

Besides, 1.05 is three sig figs, and most homebrewers want better resolution than that.
 
Epos7 said:
1.05 is three sig figs, and most homebrewers want better resolution than that.
Click to expand...

Ah, a lab guy. No wonder you seem so knowledgeable. I'm not much of a chemical engineer anymore, but I played one back in college. :)

The 1. is not significant, but only the digits after the decimal.

Cheers.
 
Perhaps calibrate the hydrometer with sucrose (table sugar) solutions, since sucrose is much less hygroscopic than maltose (major component in DME), and then do multiple measurements of actual wort with both hydrometer and refractometer to determine wort correction factor via linear regression. You can do dilutions of actual wort to get a range of SG's from wort from a single source, and do this with worts from different grain bills to collect lots of data points for the regression. Not a weekend project.

Brew on :mug:
 
dmtaylor said:
The 1. is not significant, but only the digits after the decimal.

Cheers.
Click to expand...

The 1 is significant. If it were 0.05, that would only be one significant digit, but 1.05 is three significant digits :mug:

Most homebrewers are going to want four significant digits in their gravity readings.
 
doug293cz said:
Not a weekend project.
Click to expand...

Definitely not! You make a good point though - one calibration point with tap water is only enough to calibrate the hydrometer assuming the scale of the graduations is correct and only the placement of the scale is incorrect. If the density of the hydrometer is not what is assumed by the scale of graduations, you would need a second calibration point, which could be obtained with a sucrose solution.
 
Received my 0 -12 brix hydrometer today. In 20C distilled water, it reads 0.5 brix. For some reason I was expecting better as it comes with NIST and ASTM certification. Oh well, with some adjustment it should let me check my refractometer.
 
Epos7 said:
Received my 0 -12 brix hydrometer today. In 20C distilled water, it reads 0.5 brix. For some reason I was expecting better as it comes with NIST and ASTM certification. Oh well, with some adjustment it should let me check my refractometer.
Click to expand...

What is the calibration temp printed on the paper insert?

Brew on :mug:
 
To re-post my failed brew day from my build thread, here are my notes:

another test batch tonight...failed batch 5/5

Conditioned my grains with 100ml of water and kept the mill at 0.039"
The husks remained intact, pretty cool!

I used
11lbs of pale 2-row
4 oz cascade pellets

Mashed for 90mins at 148F while recirculating. This time i hit my mash temp spot on and flucuated between 147-149 for the 90mins. I stirred 3-4 times, and had my locline attached to the lid for recirculation below the surface of the water. Didn't notice a stuck mash this time, the conditioned grains helped. Pump was turned all the way down

7.5gallon of water into kettle
~half way between 6.75 and 7 gallons post mash with 9.2 brix (1.037)
(pretty near 0.66gal if I estimate .06gal/lb grain absorption)
Boil 60 mins
post boil volume = 5.25galons at 12.2 brix (1.049)
~5.25gallon into fermenter
boil off = 1.6gallon/hour with PID at 70% (still too high)

conversion effiency: 68%
63% brewhouse efficiency (brewers friend)

whhhhhyyyyyyy??? All this effort and I only got SG 1.049

I mashed for 90mins, held a consistent mash temp with recirculation, no stuck mash, I put my water profile into Bru'n water and everything checked out fine with no need to add anything. Other brewers in my area don't need to adjust pH.

I'm tempted to go the opposite way now and crush very fine and not recirculate to see if there is a difference

Full volume mash I should be getting higher efficiency
 
Mash pH may have been VERY high because it was a SMASH beer. Specialty grains bring pH way down. Without any then I would not be surprised if pH was 6.0, way higher than the recommended 5.3-5.5.
 
dmtaylor said:
Mash pH may have been VERY high because it was a SMASH beer. Specialty grains bring pH way down. Without any then I would not be surprised if pH was 6.0, way higher than the recommended 5.3-5.5.
Click to expand...

Interesting I did not know this... I should have read more before I started using the single malt (2row or pils) as my test. I assume people that normally do SMASH beers test the pH and correct for the pH if its out of range?

So this *may* explain the poor conversion efficiency?
 
dmtaylor said:
Yeah, you're pretty much forced to add acid to SMASH beers to get pH into range.
Click to expand...

Okay that may explain the 2 out of the last 5 that I didn't meet my expected OG. But someone else locally brewed using all pilsner and got a pH of 5.6 with the local tap water

Something else is still effecting my overall mash i think
 
dmtaylor said:
Yeah, you're pretty much forced to add acid to SMASH beers to get pH into range.
Click to expand...

Here's the water calculator results with my tap water and smash...

water_2.jpg
 
So I brewed a black IPA yesterday and the recipe used specialty grains... they brought the pH down to an acceptable range (for med-dark beers) of 5.48 according to Bru'N water...yet my mash efficiency was still really low @ 69%

I am going to triple check my grain mill crush next and reduce the grind from 0.039" to 0.035"??
 
Do you guys recirculate?

If yes, I will try your method of 0.035" and double crush :mug:
 
I have a chugger pump and I do recirculate during the mash. Not 100% of the time but several times for a few minutes at a time. The bag tends to clog a bit and it drains slower than the pump sometimes.
 
Got my new knurled rollers! They arrived pretty rusty. I spent an hour and some elbow grease polishing up the axles, and I think I'll try to find a wire brush to clean up the knurling somewhat before putting them into service. I'm excited to see what kind of efficiency gains I get.

2016-12-07 16.55.32.jpg
 
Epos7 said:
Got my new knurled rollers! They arrived pretty rusty. I spent an hour and some elbow grease polishing up the axles, and I think I'll try to find a wire brush to clean up the knurling somewhat before putting them into service. I'm excited to see what kind of efficiency gains I get.
Click to expand...

Why is it rusty?
 
stever1000 said:
Why is it rusty?
Click to expand...

They must have spent some time in a humid environment before or during shipment. I was able to get them looking pretty nice using a stainless steel brush. Then I scrubbed them in some soapy water to remove all the dust, rinsed, and immediately placed them in a hot oven to prevent further rusting. I might apply a really light coat of mineral oil for added protection.
 
I was able to brew for the first time using the new knurled rollers on my mill yesterday. One observation is that the knurled rollers are slightly wider in diameter than the helical rollers, though both are specified as 2". The practical implication is that while I couldn't set the mill gap with the helical rollers below 0.022", I can now set the mill gap all the way down to 0. I found that most people are setting their mills with knurled rollers at a gap around 0.035" so I set my mill to 0.030" as I don't have to deal with stuck sparges doing BIAB. The knurled rollers set to a 0.030" gap produced a crush that was noticeably finer than what I was seeing with the helical rollers set to a gap of 0.022".

It was cold yesterday, and though I wrapped the kettle in a sleeping bag, I found the mash was losing about 1.5 degrees F per 15 minutes, so I turned the burner back on at 15, 30, and 45 minutes to bring the mash temperature back to my target 152F. The result is that the mash temperature fluctuated from 150.2F to 152F for 60 minutes. An added benefit was that the mash received a couple of minutes worth of stirring every 15 minutes.

I checked the volume markings on my kettle earlier this week and found that they are off by ~0.3 gallons. I accounted for this and am now confident my measured volumes are accurate to < 0.1 gallon.

I chose to brew the Mosaic Honey Wheat recipe for the third time, to see if I could produce any efficiency gains over my previous attempts with the helical cutters.

9 pound total grain bill (4.082kg)

4 pounds Great Western organic 2 row
4 pounds Great Western organic white wheat
1 pound Gambrinus honey malt

Mashed in 7.37 gallons of RO water with the following additions:

4.5g gypsum
4g calcium chloride (4.3g measured to account for hygroscopic nature)
2g baking soda
4mL 88% lactic acid

I heated my strike water to 157.3F, mashed in, started my timer, then stirred for a couple of minutes before closing and insulating the kettle. Where possible, I tried to take measurements with both my Milwaukee MA871 refractometer and a 9-21 brix precision hydrometer. All samples were covered and chilled to 20C prior to measurement.

15 minutes into mash:

temp - 150.5F
pH - 5.21
refractometer - 4.1

30 minutes into mash:

temp - 150.4F
pH - 5.29
refractometer - 6.0

45 minutes into mash:

temp - 150.2F
pH - 5.38
refractometer - 8.3

60 minutes (mash end):

temp - 150.7F
pH - 5.39
refractometer - 9.1
hydrometer - 9.3

After removing and squeezing the bag:

volume - 6.6 gallons
refractometer - 9.5
hydrometer - 9.8


With the new knurled rollers, I was hoping to see a better crush, improved conversion efficiency, and faster conversion (was hoping conversion would be mostly complete by 30 minutes). I did see the improved crush, and slightly improved conversion efficiency. I did not see the conversion process complete by 30 minutes, and to my disappointment the SG was higher after squeezing the bag than it was at the 60 minute mark, likely meaning that conversion had not completed.

Putting the formulas here to use, I came up with the following conversion efficiencies:

60 minutes:
refractometer - 85%
hydrometer - 87.6%

post-squeeze:
refractometer - 89.7%
hydrometer - 92.8%

So if you believe the hydrometer is most accurate, I came close to seeing good conversion after squeezing the bag. As has been discussed previously in the thread however, measured brix/sg should be the same at the end of the mash as it is after squeezing the bag. The fact that it wasn't means conversion was not complete. The mash was stirred thoroughly throughout the 60 minutes, so I can't imagine that is the issue.

I think next time I'll try dropping the mill gap to 0.025" and see what happens, but I'm no longer holding out hope. Something about my system just doesn't like producing good conversion efficiency, and after 4-5 months, 9 batches of beer, a lot of time, effort, and money, I still can't figure out what it is.
 
Hey, sounds like you're making good progress, just not quite there yet. I agree with dropping the gap to 0.025" for your next trial. I got ~99% conversion on the last batch I did (60 min mash) with a 0.022" gap (up from 0.016" I had been using) on my two roll mill.

Brew on :mug:
 
Good point, maybe I do just need to go tighter. Plenty of adjustment left with the new rollers.

Cheers!
 
Epos7 said:
I was able to brew for the first time using the new knurled rollers on my mill yesterday. One observation is that the knurled rollers are slightly wider in diameter than the helical rollers, though both are specified as 2". The practical implication is that while I couldn't set the mill gap with the helical rollers below 0.022", I can now set the mill gap all the way down to 0. I found that most people are setting their mills with knurled rollers at a gap around 0.035" so I set my mill to 0.030" as I don't have to deal with stuck sparges doing BIAB. The knurled rollers set to a 0.030" gap produced a crush that was noticeably finer than what I was seeing with the helical rollers set to a gap of 0.022".

It was cold yesterday, and though I wrapped the kettle in a sleeping bag, I found the mash was losing about 1.5 degrees F per 15 minutes, so I turned the burner back on at 15, 30, and 45 minutes to bring the mash temperature back to my target 152F. The result is that the mash temperature fluctuated from 150.2F to 152F for 60 minutes. An added benefit was that the mash received a couple of minutes worth of stirring every 15 minutes.

I checked the volume markings on my kettle earlier this week and found that they are off by ~0.3 gallons. I accounted for this and am now confident my measured volumes are accurate to < 0.1 gallon.

I chose to brew the Mosaic Honey Wheat recipe for the third time, to see if I could produce any efficiency gains over my previous attempts with the helical cutters.

9 pound total grain bill (4.082kg)

4 pounds Great Western organic 2 row
4 pounds Great Western organic white wheat
1 pound Gambrinus honey malt

Mashed in 7.37 gallons of RO water with the following additions:

4.5g gypsum
4g calcium chloride (4.3g measured to account for hygroscopic nature)
2g baking soda
4mL 88% lactic acid

I heated my strike water to 157.3F, mashed in, started my timer, then stirred for a couple of minutes before closing and insulating the kettle. Where possible, I tried to take measurements with both my Milwaukee MA871 refractometer and a 9-21 brix precision hydrometer. All samples were covered and chilled to 20C prior to measurement.

15 minutes into mash:

temp - 150.5F
pH - 5.21
refractometer - 4.1

30 minutes into mash:

temp - 150.4F
pH - 5.29
refractometer - 6.0

45 minutes into mash:

temp - 150.2F
pH - 5.38
refractometer - 8.3

60 minutes (mash end):

temp - 150.7F
pH - 5.39
refractometer - 9.1
hydrometer - 9.3

After removing and squeezing the bag:

volume - 6.6 gallons
refractometer - 9.5
hydrometer - 9.8


With the new knurled rollers, I was hoping to see a better crush, improved conversion efficiency, and faster conversion (was hoping conversion would be mostly complete by 30 minutes). I did see the improved crush, and slightly improved conversion efficiency. I did not see the conversion process complete by 30 minutes, and to my disappointment the SG was higher after squeezing the bag than it was at the 60 minute mark, likely meaning that conversion had not completed.

Putting the formulas here to use, I came up with the following conversion efficiencies:

60 minutes:
refractometer - 85%
hydrometer - 87.6%

post-squeeze:
refractometer - 89.7%
hydrometer - 92.8%

So if you believe the hydrometer is most accurate, I came close to seeing good conversion after squeezing the bag. As has been discussed previously in the thread however, measured brix/sg should be the same at the end of the mash as it is after squeezing the bag. The fact that it wasn't means conversion was not complete. The mash was stirred thoroughly throughout the 60 minutes, so I can't imagine that is the issue.

I think next time I'll try dropping the mill gap to 0.025" and see what happens, but I'm no longer holding out hope. Something about my system just doesn't like producing good conversion efficiency, and after 4-5 months, 9 batches of beer, a lot of time, effort, and money, I still can't figure out what it is.
Click to expand...

Your conversion was likely done at 30 minutes but when conversion happens the wort is more dense than water and sinks, leaving you with less dense water near the surface. During the rest of the time the sugary wort will disperse into the less dense water making you think that you are still getting conversion. Next batch, stir very well before taking your refractometer sample. I'll bet that your reading will not change from the 30 to 60 minutes if you get the wort mixed well.

On my last batch I took a refractometer sample about 3 minutes into the mash, then another one at 15 minutes and found that the gravity had gone down. I know that with some religions you can unconvert but I doubt that I had unconversion in my mash.
 
RM-MN said:
Your conversion was likely done at 30 minutes but when conversion happens the wort is more dense than water and sinks, leaving you with less dense water near the surface. During the rest of the time the sugary wort will disperse into the less dense water making you think that you are still getting conversion. Next batch, stir very well before taking your refractometer sample. I'll bet that your reading will not change from the 30 to 60 minutes if you get the wort mixed well.

On my last batch I took a refractometer sample about 3 minutes into the mash, then another one at 15 minutes and found that the gravity had gone down. I know that with some religions you can unconvert but I doubt that I had unconversion in my mash.
Click to expand...

It's not that there is higher SG wort formed near the top of the mash, that then sinks, it's just that higher SG wort forms lower in the mash. What happens, particularly in a thin mash, is the grain settles towards the bottom of the vessel, so that is where more sugar gets created, and higher SG wort exists, because that's where the starch is. So, the SG stratification is caused by where the sugar is actually formed. And, it takes way more stirring than you think it does to get the wort homogenized. (I got bit by insufficient mixing of initial and sparged wort, leading to an erroneously low pre-boil SG measurement, on my last batch. And I thought I stirred pretty well.)

Brew on :mug:
 

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