Effect of Mill size

[starsman20]

I have been battling a 65 to 70% efficiency since starting all grain. I have a herms system and I was expecting a higher efficiency. So for the brew this morning I tried something a little different. I made an adjustment on my barley mill. I had been using it as it came. It was supposed to be 1mm I think but I did not measure it. I rotated the adjustment nobs about 10 degrees. The difference in distance of the rollers was barely noticeable but when I milled my grain it was a little more powdery. Into the BK went 7 gallons at 1.040. Expected was 1.042 but at 6.25 gallons. I collected a little too much. For the first time ever I have a pretty good boil over. Maybe my fermcap is expired but it was a doozy. I am thinking the efficiency will be garbage from the lost wort.. Post boil volume was 5.75 @ 1.053. 1.047 was the target. First time I have been high without making a grain adjustment. Even with the boil over beersmith calculates the efficiency at 85%. Without the boil over I think it would have been a little higher. Everything else about my brew day was pretty normal. Mashed at 152 for an hour. I did not reach the mashout temp of 168, gave up at 164. Fly sparged at 170. So the question is can such a small change of the mill gap make that much of a difference in efficiency? I am brewing again next weekend so I will try to duplicate this.

 

[Oginme]

Short answer: yes.

My efficiency was bouncing from the high 60's to mid 70's using double milled grain from the LHBS. I bought a grain mill this past spring and have had my efficiency jump from an average of 72% up to a very consistent 86.5% It took me a couple of batches to make sure the jump was real, and so I ended up with a lot more wort than I needed at target OG for the first two batches. After recalculating for that, I've been had very consistent grinds and very consistent efficiency numbers (all between 86% and 87%).

 

[tootal]

+1! The finer the milling the better the efficiency, HOWEVER, for a home brewer getting too much "dust" and grinding your hulls will give you a stuck mash. Just make sure that your milled malt still shows whole hulls in the mix. The hulls are what helps you sparge, sort of like using rice hulls. Another thing is you should get a set of feeler gauges so you can be sure you are even across the rollers. Setting the gap for each mill is critical as not all are the same. It seems the small rollers require less gap. Mine has 5" rollers and are set at .069" yet we get 86 percent efficiency. Your's came at .039".
You just need to find your sweet spot and be sure it's even across the rollers and the hulls are still whole.

 

[kal]

+1! The finer the milling the better the efficiency

On some setups only, and mostly only true for those that do not use recirculation setups during mashing (HERMS or RIMS).

Mill too fine for a RIMS/HERMS setup and you'll impede flow and have poor extraction (almost like a stuck mash that you describe).

I purposely mill a bit loose (around 0.045" gap) because of this. I could probably go as high as 0.060" without any issues and have the same efficiency.

Sabco had a good article about this in their blog some time ago that I agree with 100%:

https://brewmagic.com/blog/follow-me-to-higher-efficiencies/

Kal

 

[Moose1231]

Something similar happened to me last weekend. I was getting poor efficiency but my procedure was the same. I even had one batch with less than 60%, which was unusual. I asked my LHBS to pass it twice in his mill and I got something like 77% efficiency. It's not the first time I hear that the crush size has a massive importance

 

[tootal]

On some setups only, and mostly only true for those that do not use recirculation setups during mashing (HERMS or RIMS).

Mill too fine for a RIMS/HERMS setup and you'll impede flow and have poor extraction (almost like a stuck mash that you describe).

I purposely mill a bit loose (around 0.045" gap) because of this. I could probably go as high as 0.060" without any issues and have the same efficiency.

Sabco had a good article about this in their blog some time ago that I agree with 100%:

https://brewmagic.com/blog/follow-me-to-higher-efficiencies/

Kal

Did you not read the 'HOWEVER' part? What I said is true. Large breweries mill their malt into talcom powder but they can do this because they have rakes in their lauter tuns that can get the flow going again after it "sticks". In order to be more profitable they do this because it mashes faster and is more efficient. They run "vorlauf" pumps to recycle just like a RIMs/HERMS but yet again, they have rakes that allow them to do it.

HOWEVER! For the home brewer this is not feasable, that was my point.

 

[TIPA0303]

Boil overs shouldn't affect your final gravity (assuming you don't cut your boil short to compensate for volume). You are losing a homogeneous composition of sugars in a boil over. This will only result in decreased volume, not decreased gravity.

 

[kal]

Did you not read the 'HOWEVER' part?

Yes - sorry - true. I should have simply posted my information as a reinforcement to what you wrote. Sorry for the confusion.

Kal

 

[Brewtah]

I am glad this Thread came up. My efficiency is terrible on a P Mash. I know a good bit of the reason is inexperience. My efficiency has consistanty been 55%-57% every batch. I am thinking I should have my LBS to double mill. Or should I ask about mill setting?

 

[grathan]

I also recently went from high 60% to high 80% when I adjusted the mill.

Never had a stuck mash. Is it the compaction on top of the grain bed or the suction at the bottom that clogs usually?

 

[IslandLizard]

I use credit cards to adjust the mill and a feeler gauge and calipers for "calibrating" the cards. The thinner American Express Cards we get in the mail almost weekly are great! They come in at 0.023" which sets my 1.5 inch MM2 @ 0.028" between the top of the knurls, while I can still slide it. Works great! With 20% wheat malt I don't need rice hulls.

0.060" sounds really coarse compared to that. Maybe there's a significant difference in the knurls. And roller size and # of rollers play a large role too.

Oh, I batch sparge, and efficiency is around 80% with that setup.

 

[stpug]

I use credit cards to adjust the mill and a feeler gauge and calipers for "calibrating" the cards. The thinner American Express Cards we get in the mail almost weekly are great! They come in at 0.023" which sets my 1.5 inch MM2 @ 0.028" between the top of the knurls, while I can still slide it. Works great!

Beautiful idea lizard; and so simple!!! I'm off to go check thicknesses of various items now

 

[tootal]

Yes - sorry - true. I should have simply posted my information as a reinforcement to what you wrote. Sorry for the confusion.

Kal

Cool man. I love your basement, by the way!:rockin:

 

[IslandLizard]

Beautiful idea lizard; and so simple!!! I'm off to go check thicknesses of various items now

Oh, it wasn't my idea, I read it somewhere on the forums here. I just extended it with the calibration method. Easier to slide a used card than to juggle metal gauges.

Regular CCs are thicker and measure 0.031" which sets the gap at around 0.035" between the knurls, which is often used as the gap to start with.

I read somewhere here to "tighten the gap until it scares you" [sic]. That 0.028" indeed looks scary, and I may give it just another nudge!

Sometimes I even mill twice.
And if you feel it helps, you could mill your different grains at different gaps. Like rye kernels are very small, so a bit tighter gap for them may prevent a lot from passing through half milled.

For some reason I think the different manufacturers use different knurls though, like steepness and size may vary a quite a bit.

 

[dryboroughbrewing]

I mill pretty finely at .030. In the early days of my RIMs system I ran into some sticking issues, however a better return arm, and switching to wet milling my grains (3% water by weight) really have sorted out that issue. The last beer I did in fact was my hoppy wheat, which is 60% wheat.