I recently brewed what was going to be a double IPA with a target OG of 1.075 and ABV of around 8%. It ended up being 1.060. I use a cooler with a stainless steel braid for false bottom and I always do a double batch sparge with 3 gallons first and then however much is needed (usually around 2 gallons) after that. I stir thoroghly on both sparge steps. I usually hit my numbers or get pretty close. As far as I can tell I did everything properly the way it was set up in beer smith. My volumes were right. My mash temperature was spot on and held well until the end of the mash. So I'm trying to figure out why my OG was so off and I'm wondering if it has something to do with sparging. I've heard that its more difficult sometimes to hit numbers with bigger beers such as this. Does anything in my process seem off? One thing I have been doing recently is heating my sparge water to 168F per beer smiths instructions as opposed to what I used to do and what I know some others do which is heat it to 180F so that it will get down to around 168F after heat loss. Could this temperature difference potentially be the problem?
Lauter Efficiency Issue?
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The first three causes of lower efficiency are:
1. The crush of the grain.
2. The crush of the grain.
3, The crush of the grain.
While it is expected to lose efficiency with a higher OG because your mash thickness makes it more difficult to get the grains all stirred in, I'd be looking at the grains to see how well crushed they are. Someone may have adjusted the mill between your two batches and that can really affect the outcome. It's one of the reasons I often advocate for owning the mill so you get to do the adjusting.
1. The crush of the grain.
2. The crush of the grain.
3, The crush of the grain.
While it is expected to lose efficiency with a higher OG because your mash thickness makes it more difficult to get the grains all stirred in, I'd be looking at the grains to see how well crushed they are. Someone may have adjusted the mill between your two batches and that can really affect the outcome. It's one of the reasons I often advocate for owning the mill so you get to do the adjusting.
To throw this out there, too: for batch sparging, the temp of the sparge water doesn't impact lauter efficiency. Hell, with batch sparging not much does. As RM-MN mentioned, you probably have a conversion issue as opposed to a lautering issue. Heating that sparge water to 168°F is more for purposes of a mashout step - which is unnecessary for batch sparging. To be accurate, though, you need to get the mash and runoff itself to 170°F. Using 170°F water will just raise it a little bit, not actually denaturing the enzymes. Despite batch sparging, myself, i actually use boiling water to sparge. I know you can batch sparge with cold water, even, but hot water gets me that much closer to a boil after runoff. One thing i suggest is to take a grav reading of your second batch sparge runoff. This would give you an idea of how much sugar you're leaving in the grain, and thus, how efficient your sparging method is.
Digging deeper into the conversion issue: without knowing the grainbill, possibly this was an 'outlier' recipe? Something was different for this one that isn't the case for your typical brews? For example, if this was a stout vs all your other IPAs, and you didn't do anything to address mash pH, maybe there was an issue there? Not saying that having your mash pH off will cause a -0.015 SG difference, but you get the idea.
Digging deeper into the conversion issue: without knowing the grainbill, possibly this was an 'outlier' recipe? Something was different for this one that isn't the case for your typical brews? For example, if this was a stout vs all your other IPAs, and you didn't do anything to address mash pH, maybe there was an issue there? Not saying that having your mash pH off will cause a -0.015 SG difference, but you get the idea.
It is normal to see reduced lautering efficiency with bigger beers although probably not to the extent you described.
The normal drop in lauter efficiency is due to dilution math. In your first run-off you remove some portion of the wort and leave behind a wet grain bed. All the moisture left in the grain has the same concentration of sugars that the initial runoff had. The amount of sugar left in the moisture in the grain bed depends on the quantity of grain x the concentration of the wort. A larger grain bill will retain more wort, and if you are like me and bigger grain bills with a thicker mash (due to mash tun volume constraint) then the increase in concentration also means even more sugar left behind. When you sparge the same issues impact your efficiency and in addition it is just harder to thoroughly mix that larger grain bill with the sparge water. If you get less than perfect mixing you are again taking an efficiency hit as the runoff wort can't possibly be more concentrated than the wort left behind in the grain bed.
As you described your process and given this was a big but not huge beer I suspect @RM-MN is probably right. Crush is pretty critical to efficiency. I believe crush makes most of its impact on mash conversion/mash efficiency. I see this in my brewing, with a fine crush I can get quite close to 100% conversion as measured by concentration of sugar in the circulating mash wort, with a coarse crush it is harder to get there and I may need to extend the time of the mash to get even above 90% conversion. Conversely I find a coarser crush makes lautering much easier and if I have room in the MLT I may choose to give up a bit of efficiency in order to work with a looser, easier flowing grain bed and so would back off a bit on the crush. There is a happy medium on this and I had it dialed in on my Barley Crusher but am still working on finding the sweet spot on my new monster mill. After 3 batches with low efficiency I think I figured out the issue (my gap wasn't clamped tight enough) and the fourth batch came in 10 points high
but it was a PITA dealing with the sticky mash.
The normal drop in lauter efficiency is due to dilution math. In your first run-off you remove some portion of the wort and leave behind a wet grain bed. All the moisture left in the grain has the same concentration of sugars that the initial runoff had. The amount of sugar left in the moisture in the grain bed depends on the quantity of grain x the concentration of the wort. A larger grain bill will retain more wort, and if you are like me and bigger grain bills with a thicker mash (due to mash tun volume constraint) then the increase in concentration also means even more sugar left behind. When you sparge the same issues impact your efficiency and in addition it is just harder to thoroughly mix that larger grain bill with the sparge water. If you get less than perfect mixing you are again taking an efficiency hit as the runoff wort can't possibly be more concentrated than the wort left behind in the grain bed.
As you described your process and given this was a big but not huge beer I suspect @RM-MN is probably right. Crush is pretty critical to efficiency. I believe crush makes most of its impact on mash conversion/mash efficiency. I see this in my brewing, with a fine crush I can get quite close to 100% conversion as measured by concentration of sugar in the circulating mash wort, with a coarse crush it is harder to get there and I may need to extend the time of the mash to get even above 90% conversion. Conversely I find a coarser crush makes lautering much easier and if I have room in the MLT I may choose to give up a bit of efficiency in order to work with a looser, easier flowing grain bed and so would back off a bit on the crush. There is a happy medium on this and I had it dialed in on my Barley Crusher but am still working on finding the sweet spot on my new monster mill. After 3 batches with low efficiency I think I figured out the issue (my gap wasn't clamped tight enough) and the fourth batch came in 10 points high
but it was a PITA dealing with the sticky mash.
To hit your pre-boil SG target, you need to have a predictable mash efficiency, and control your volume precisely. To hit your OG target, you also have to control your boil off volume.
Your mash efficiency is made up of two factors: conversion efficiency and lauter efficiency. Lauter efficiency (for batch or no sparge) varies with the grain weight to pre-boil volume ratio. If you increase the grain weight for the same pre-boil volume, the lauter efficiency will go down. To keep lauter efficiency constant, you would have to increase your pre-boil volume by the same percentage as you increased your grain weight, and then boil off the excessive water to hit your post-boil volume target. This becomes unmanageable when boil times start exceeding 2 hrs. So, you usually end up taking a lauter efficiency hit with bigger beers. The following chart shows how lauter efficiency varies with grain to pre-boil ratio for various numbers of sparge cycles, and two different grain absorption rates (0.12 is typical for an MLT.)
Conversion efficiency can reach 100%, but should be 95% or better. The primary determinant of conversion efficiency is fineness of crush (as stated previously.) Mash time, temp, and pH also play lessor roles in conversion efficiency. You can easily measure your conversion efficiency using the method here.
Mash efficiency is easily calculated using any common brewing software. Once you have you mash efficiency and conversion efficiency, you can calculate your actual lauter efficiency as:
Sparge water temperature makes no difference IF your conversion is essentially complete at the end of your allotted mash time. If conversion is not complete, then hot sparge water will heat up the mash, accelerating the conversion process until the amylase enzymes are all denatured. In the case of incomplete conversion, hot sparge water can drive conversion more towards completion, and give increased conversion efficiency and thus increased mash efficiency. This is what is being observed by brewers who say that a mash out improves their efficiency.
Brew on
Your mash efficiency is made up of two factors: conversion efficiency and lauter efficiency. Lauter efficiency (for batch or no sparge) varies with the grain weight to pre-boil volume ratio. If you increase the grain weight for the same pre-boil volume, the lauter efficiency will go down. To keep lauter efficiency constant, you would have to increase your pre-boil volume by the same percentage as you increased your grain weight, and then boil off the excessive water to hit your post-boil volume target. This becomes unmanageable when boil times start exceeding 2 hrs. So, you usually end up taking a lauter efficiency hit with bigger beers. The following chart shows how lauter efficiency varies with grain to pre-boil ratio for various numbers of sparge cycles, and two different grain absorption rates (0.12 is typical for an MLT.)
Conversion efficiency can reach 100%, but should be 95% or better. The primary determinant of conversion efficiency is fineness of crush (as stated previously.) Mash time, temp, and pH also play lessor roles in conversion efficiency. You can easily measure your conversion efficiency using the method here.
Mash efficiency is easily calculated using any common brewing software. Once you have you mash efficiency and conversion efficiency, you can calculate your actual lauter efficiency as:
Lauter Efficiency = Mash Efficiency / Conversion Efficiency
If your lauter efficiency is less than what is shown on the chart, then you should look to improve your lauter process (although OP sounds like they are doing things right.)Sparge water temperature makes no difference IF your conversion is essentially complete at the end of your allotted mash time. If conversion is not complete, then hot sparge water will heat up the mash, accelerating the conversion process until the amylase enzymes are all denatured. In the case of incomplete conversion, hot sparge water can drive conversion more towards completion, and give increased conversion efficiency and thus increased mash efficiency. This is what is being observed by brewers who say that a mash out improves their efficiency.
Brew on
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