Author Topic: Conversion Efficiency  (Read 3887 times)

Online denny

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Re: Conversion Efficiency
« Reply #15 on: November 21, 2012, 12:03:21 PM »
I was trying to collect 5.5 gal, but I think I don't think beercalculus is very good at factoring that in.

This is actually the first time I have tried fly sparging, I usually batch sparge with the same results. I was trying the continuous sparge to see if investing in a proper fly sparging set-up might help.

According to Kai's formulas, I had a conversion efficiency of 99%, but I'm not sure I understand how that could be possible. Does his table assume qts of water per pound of base malt? or the entire grain bill?

If you're shooting for 5.5 gal. in the fermenter, then 1.066 is the estimate from PM. 


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Offline malzig

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Re: Conversion Efficiency
« Reply #16 on: November 24, 2012, 01:30:27 PM »
my OG with a 75% efficiency should have been 1.079...
 (12lbs 2-row, 2.5 lbs specialties) I mash in an igloo cooler with a 1.5 qt/lb water:grain ratio. This time, that ratio was even a bit higher...I had to add a little more than a galolon of boiling to the mash, so my ratio was closer to  1.94.

I collected my first runnings, and let them cool while I was lautering. At 90°F, the gravity was 1.050. In my mind, my first runnings should have been over 1.080.
Ignore the sparge, for now, you could screw around a lot with how fast you add or drain, what volumes you use, what type of manifold you have, or how long you let the sparge water sit, and you might see a few points improvement, but you would be chasing the wrong problem.  What you have is partially a math problem, but primarily a conversion problem.

First off, if you mashed 14.5# of grain with ~7 gallons, you might expect a  first running gravity of 1.065 with 100% conversion, not "over 1.080".  Assuming that you had good mixing during your vorlauf, at 1.050 you probably had about 75% conversion.

Secondly, this was probably never going to be more than 5.5 gallons of a 1.067 beer, if everything had gone well and you got 100% conversion and the ~80% overall mash efficiency expected for a beer of this size. 

Finally, with your 75% conversion and a quart of dead space, you would expect 1.036 at 8.5 gallons in the kettle.  You got 1.035, so you probably had 95-100% lauter efficiency.

Instead of following a list of random suggestions, some of which would be used to fix problems you don't have, analyze your system like this and you can identify where your problem lies.  If you don't measure basic elements of your process properly, like conversion and lauter efficiency, you'll waste a lot of time making random changes instead of informed decisions. 

In your case, focus on things that will improve conversion.  Crush is most important, then comes pH and mash schedule.  Optimized crush, could easily gain you 10%+ conversion.

I've never used those pH strips, so I can't say if they are accurate or not.  If your pH is really 6.0, though, you need to get it down, because that is high enough to have an effect on your efficiency.  Probably closer to a 5% hit than the 25% that you are seeing, though.

I'd try an alpha amylase rest, too.  Mash at your usual temperature, say 152F, for a half hour or so, then infuse enough hot water to bring the temperature up around 158-162F and thin your mash out to ~1.7 qt/#.  Some brewers can gain 10%+ conversion efficiency with this change.
According to Kai's formulas, I had a conversion efficiency of 99%, but I'm not sure I understand how that could be possible. Does his table assume qts of water per pound of base malt? or the entire grain bill?
You need to include the entire grain bill for Kai's table to work.  Specialty malts contribute nearly as much to gravity as base malts, and Kai's chart is assuming a recipe with a somewhat average mix of grains.
« Last Edit: November 24, 2012, 03:48:26 PM by malzig »

Offline neemox

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Re: Conversion Efficiency
« Reply #17 on: November 24, 2012, 01:59:40 PM »
Wow, Great Response, thank you!! This is the kind of post I was hoping for when I first asked the question. I'll get some pH strips with better accuracy and measure again, hopefully that could be my issue, but I kind of doubt it. Most of my brewing buddies never even bother to measure their pH, use the same water, and relatively similar grain bills. They never seem to have an issue. (Then again, I also don't think they typically measure efficiency...)

I'd try an alpha amylase rest, too.  Mash at your usual temperature, say 152F, for a half hour or so, then infuse enough near hot water to bring the temperature up around 158-162F and thin your mash out to ~1.7 qt/#.  Some brewers can gain 10%+ conversion efficiency with this change.


So with two rests like this, should I aim for 1.7qt/# at my strike, or for the final mash ratio (after the addition to bring the temp yup for the second rest)?
Quote
You need to include the entire grain bill for Kai's table to work.  Specialty malts contribute nearly as much to gravity as base malts, and Kai's chart is assuming a recipe with a somewhat average mix of grains.
I was assuming the entire grain bill, but I was making a math error. This calculation needs to be in points instead of SG. (SG-1).  So in reality, I had about an 84% conversion efficiency, which as you pointed out definitely suggests my conversion, and not my lauter.

Again, thank you so much. Is there a way to measure the crush that I am getting from my LHBS? The grain looks very well crushed,with lots of dust and no intact hulls, but perhaps I need to get more analytical here. I asked them what their mill was set to, but they didn't know. Is that something I could measure for/with them?

Offline malzig

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Re: Conversion Efficiency
« Reply #18 on: November 24, 2012, 04:51:58 PM »
I'll get some pH strips with better accuracy and measure again, hopefully that could be my issue, but I kind of doubt it.
I'd try an alpha amylase rest, too.  Mash at your usual temperature, say 152F, for a half hour or so, then infuse enough near hot water to bring the temperature up around 158-162F and thin your mash out to ~1.7 qt/#.  Some brewers can gain 10%+ conversion efficiency with this change.
So with two rests like this, should I aim for 1.7qt/# at my strike, or for the final mash ratio (after the addition to bring the temp yup for the second rest)?
Quote
You need to include the entire grain bill for Kai's table to work.  Specialty malts contribute nearly as much to gravity as base malts, and Kai's chart is assuming a recipe with a somewhat average mix of grains.
I was assuming the entire grain bill, but I was making a math error. This calculation needs to be in points instead of SG. (SG-1).  So in reality, I had about an 84% conversion efficiency, which as you pointed out definitely suggests my conversion, and not my lauter.

Again, thank you so much. Is there a way to measure the crush that I am getting from my LHBS?
pH is generally not that much of an issue for conversion, though it can be and I've known brewers from areas with poor water whose conversion was impacted.  I'd move it down the list, but you might want to reign it in to prevent astringency in your beer.  Do you know if you are in an area with high bicarbonate?

For the alpha amylase rest, I aim for 1.7 qt/# or higher after the temperature step.  (I actually shoot for ~ 2 qt/# but it depends on the grist mass.)  The reason I recommended this is that I believe that it can make up for a less than optimal crush.  It's tough when you are getting your malt crushed by a homebrew shop. 

You could measure their gap, and I'm sure you could find plenty of threads with a long list of gap sizes that brewers prefer, but I have always optimized crush by gradually closing the gap until I got near complete conversion.  Ultimately, I believe that any serious homebrewer needs to break down and get a mill so that they have control over this aspect, but it took me 20 years to do that, so I can sympathize with brewers who don't.

One easy thing to try at a homebrew shop is to ask for them to crush the grain twice.  That's probably not going to be optimal, but it usually makes the largest chunks a bit smaller and can improve conversion in a case like yours.  What is common is that the larger grain chunks are not gelatinizing well.  Since we usually mash just below the optimal gelatinization temperature, making the grain smaller, thinning the mash, and raising the temperature can all tend to accomplish the same thing: making the starch available to amylase.

I think you might still be a little generous in your interpretation of Kai's equations, unless I'm screwing up the math or misunderstand your volumes and gravities.  I've tried using them a couple ways and the highest conversion I have calculated for you was about 77%.

Offline neemox

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Re: Conversion Efficiency
« Reply #19 on: November 24, 2012, 05:11:07 PM »

I think you might still be a little generous in your interpretation of Kai's equations, unless I'm screwing up the math or misunderstand your volumes and gravities.  I've tried using them a couple ways and the highest conversion I have calculated for you was about 77%.

Hmm ok. Maybe you can walk me through this table then... I was figuring 14.5 lbs of grain, 7 gal (28 qts) of water gives ~1.94 qt/#, so I should have had a FW of ~1.065. I got 54 points, so (54/65) *100%= 83%. Where did I screw this up?

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Re: Conversion Efficiency
« Reply #20 on: November 24, 2012, 05:41:46 PM »
Hmm ok. Maybe you can walk me through this table then... I was figuring 14.5 lbs of grain, 7 gal (28 qts) of water gives ~1.94 qt/#, so I should have had a FW of ~1.065. I got 54 points, so (54/65) *100%= 83%. Where did I screw this up?

In the first post, you said that the first runnings were 1.050 SG.
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Offline neemox

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Re: Conversion Efficiency
« Reply #21 on: November 24, 2012, 05:43:41 PM »
Ahh, indeed I did. But that was at 90. I should have done the temperature correction in my OP. @60, that would be 1.054 according to my calculator.

Offline malzig

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Re: Conversion Efficiency
« Reply #22 on: November 24, 2012, 06:21:39 PM »
Ahh, indeed I did. But that was at 90. I should have done the temperature correction in my OP. @60, that would be 1.054 according to my calculator.
Sounds right.  My mistake.  Like Denny, I was remembering the 1.050, not the 90F.