I was given the opportunity to get this mill early and do some testing. I put it though its paces and here is what I found!
The mill arrived early in December of 2019, and was packaged well.
Assembly was a breeze, as it was just 4 screws for the hopper
The first thing I noticed was the weigh of this thing, it was easily 40+lbs and built VERY well. The super large stainless steel 4″ fluted rollers are super high quality. I was anxious to get to milling, but first I had to play with the tool less gap adjustment. The gap adjustment featured 11 preset gap settings, from +5 though -5 (coarse to fine). Setting the gap is loosening the thumbscrew, moving the bar, and then re-tightening the thumb screw in the corresponding hole for the number wanted. I will detail more about it further on.
As you can see the gap adjustment is a total game changer. You can even change on the fly to another preset midway though a hopper full of grain! All while keeping both rollers in proper alignment, I can’t say enough how great this feature is. Now, to what this is all about… Milling
For the milling tests, I wanted to try and standardize everything. So for all tests I used the same grain, same grain amount, same temperature, same humidity, basically tring to keep all possible variables constant. I then put all the samples though the proper milling sieve tests using #14, #30, and #60 sieves. Here you will not only get a good visual of what the presets crushes look like, you will get the ACTUAL sieve analysis, which I don’t see happening anywhere else. However before we get into these results, I think we should discuss sieve analysis and what its about.
Here at Low Oxygen Brewing we pride ourselves on using professional brewing methods, and getting a proper crush is definitely one of them. We have detailed this on the blog already with our http://www.lowoxygenbrewing.com/uncategorized/grain-conditioning/ post. There is also kind of an unspoken crush rule, and it’s that Germans generally crush finer than the Americans, but as with nearly all things Germans do, it’s for a reason (faster conversion, more potential conversion, while using the Hochkurz mashing regimen).
When Rolec set up our new brewhouse, one of the things Harry Klaussner, the brewmaster, did was to adjust the gap settings on our four-roll Kunzel mill. He did this by eyeball. We started up the conveyor and the mill, and Harry knelt on top of the grist case and thrust his right arm into the inspection port at the top. He reached under the cascade of milled grain that was emerging from the bottom of the mill, caught a handful, then carefully withdrew it and peered at the sample. Then he stood up, grabbed a wrench, went round to the adjustment side of the mill and changed the settings. He did this three times. After the last adjustment he pronounced the crush satisfactory.
This did not surprise me, because this is the way I had always done it. What surprised me was how fine the crush was. Apparently the Germans have different standards. All I said was “Okay,” though, after all it was their brewhouse.
Kunze has a whole chapter dedicated to malt, after all it is the “soul of beer”. We have gone over these things on the blog already so no need to rehash everything but high level overview would be proper milling means:
- Avoid Unground Kernels – Losing extract and efficiency
- Prevent Husk Going into Kettle – tannin extraction, preventing husk in kettle, also starch extraction from unground or under modified in lautering. The fact that it’s so easy with modern malt is shown in how little attention milling is giving relative to other aspects of brewing. Looking at you- crush until your scared/flour folks. Husks are astringent!
OK with that said lets get into crush, and after we see the crush and sieve results we will further detail what it all means.
All milling was done with Barke Vienna malt.
4oz measured samples.
Milling was started at +5 which is the coarsest setting.
+5 = 2.0mm or .078
+4 = 1.85mm or .072
+3 = 1.7mm or .066
+2 = 1.55mm or .061
+1 = 1.4mm or .055
0 = 1.25mm or .049
-1 = 1.1mm or .043
-2 = .95mm or .037
-3 = .8mm or .031
-4 = .65mm or .025
-5 = .5mm or .019
Overall crush of the 11 presets
What are the results of the visual crush analysis?
Based on visual tests, I chose +1 (1.4mm or .055) to give what I thought was a pretty close representation of what I look for in a crush. It looked more traditional to me. Here it is again for reference.
What are the results of the sieve tests, how do I read them and what am I looking for?
Sieve tests are used to determine the middle ground between yield, lautering and quality. Commercial standards look for:
- #14 – 50-60%
- #30 – 25-32%
- #60 – 7-11%
- Pan – 5-10%
Briess’ criteria is that 50 – 55% on the #14 top screen is normal, however many would contend that up to 60% is acceptable. To summarize their findings:
A coarse crush (78% on #14) gave 85% brewhouse efficiency and 96 minute wort collection time.
A normal crush (53% on #14) gave 91% brewhouse efficiency and 94 minutes wort collection time.
A fine crush (25% on #14) gave 92% brewhouse efficiency and 143 minutes collection time.
All this lines up perfectly with intuition and experience. Uncrushed kernels represent a direct loss of extract, and what you find when you examine coarsely crushed malt samples is a proportion of same. Thus, the large gap (relatively speaking) in brewhouse efficiency between coarse and normal crushed malt. In a normal sample, you will find no uncrushed kernels. And therefore, a fine crush gives only a small increase in efficiency, but a large increase in lauter time (and difficulty). Again looking at you, flour boys.
Sieves are an invaluable tool to be able to get the proper settings for all malt, as most different kernel sizing is different based on the grain. This is ironic, because based on MY visual inspection of the crush I guessed a ~70% (#14) and therefore would have lost some brewhouse efficiency. The tool less gap adjustment means I can run a quick test of say, my wheat malt, and adjust gap and get the proper crush on it. Meaning I won’t be losing any efficiency due to have to set a “catch all” gap, and lose efficiency or have to double crush.
Now, what does this all mean?
Firstly, this mill uses rollers that are 2x bigger than the biggest homebrew mill on the market, it also spins them faster. So therefore you can’t equate these mill gaps to gaps you are currently using with your mills. In fact, something like mill RPM makes quite a bit of difference in crush and gap in normal mills, changing 50rpm on the rollers will drastically change the crush. So with that said, you can’t imply the results with any of these numbers directly to the mill you are using today. If you want to know for sure, YOU will have to do the sieve tests.
I have found that even on the finest crush settings, there is very little shredding of the husks, I attribute this due to roller size and the fact this mill spins the rollers at differential speeds (another first for the home brew world).
So who is the winner today?
Well for me it’s……………………
-1 = 1.1mm or .043
It hits all the criteria I need for my brewery:
#14 – 50-60%
#30 – 25-32%
#60 – 7-11%
Pan – 5-10%
Ironically as you can see it is NOT the one I chose in the visual inspection.. Case in point!
Here is a graph of the milling:
I hope this not only demonstrates the importance of a high quality mill, but to understand how to properly mill your malt.