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What is the best crush size for biab?

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Finlandbrews

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If milling size or crush size in non-biab method is a compromise between husks sizes (for filter bed) and availability of starches for optimized extraction efficiency, can't we think of the best crush size for biab as being "the smallest crush size possible as long as we can ensure maximum of husks to stay in the bag"?

Isn't the crush size different from biab compare to non-biab? If not why?
 

Yooper

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You can crush to flour if you want.

The only way crush size matters is to keep you from getting a stuck mash or sparge. If you can crush to flour whether it's BIAB or in a traditional MLT, that's fine. If you need a coarser crush to avoid being unable to lauther, that's fine too.
 

solbes

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Keep in mind the more flour you make in a fine crush, the more trub you create in the bottom of the fermenter. Even with a high quality bag, which I definitely recommend.

I think I set my mill to .030", verified with a gage pin. I could go a little finer for sure, but don't feel like I need to. My BIAB efficiency range is between 73 and 90%. depending on grain bill size.
 

wilserbrewer

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Yea, I wouldn't try and grind to flour at all....more like a coarse corn meal consistency with every kernel of grain well fractured into several pieces is plenty fine enough.

Fwiw, I use the same crush for BIAB as I do for my cooler MT with a stainless braid.

Just a very thorough crush, nothing crazy for me....
 

ArcLight

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I grind it to dust, and pat the bag a few times to shake off the excess dusk before putting it in the kettle. The only problem is I have quite a lot of dough balls, so I'm going to try pouring in the crushed grain, rather than putting the bag (containing the grain) right in.
 

tknice

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I grind it to dust, and pat the bag a few times to shake off the excess dusk before putting it in the kettle. The only problem is I have quite a lot of dough balls, so I'm going to try pouring in the crushed grain, rather than putting the bag (containing the grain) right in.
Yeah you want to "dough in" by pouring the grain slowly and moving the water back and forth using the mash paddle in your other hand. It's rare to see a dough ball doing it this way.
 

Gavin C

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Coarse corn meal for me too. The narrowest setting on my mill gets me that.

A single pass takes a couple of minutes to mill grains for a 5.5 gallon batch.

Decent balance between effort and grist-size IMO

Some flour in there but that's not my objective.
 

tknice

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Forgot to mention you can use a credit card to set the gap. That will get you to a .9mm gap which should be perfect for a single pass crush.
 
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If you are planning on using a pump to recirculate the wort during the mash then you will need a .35in or larger crush. I am currently using a .45" crush with my biab/ pump set up with good results.
 

TexasWine

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Yeah you want to "dough in" by pouring the grain slowly and moving the water back and forth using the mash paddle in your other hand. It's rare to see a dough ball doing it this way.
I just put the whole bag o' grains in all at once and stir out the dough balls with a spoon and whisk. Works great.
 

wilserbrewer

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I just put the whole bag o' grains in all at once and stir out the dough balls with a spoon and whisk. Works great.
Me too, with only two hands available, I have found the best easiest fastest way is to swiftly dump the entire grain bill, then work it out immediately with the paddle / spoon.
 

Gavin C

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+1

Creating dough-balls is an absolute impossibility with full-volume mashing in my experience.

Dump it all in in a second or two and stir. Simple.
 

tknice

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+1

Creating dough-balls is an absolute impossibility with full-volume mashing in my experience.

Dump it all in in a second or two and stir. Simple.
hmm, I've always been scared to try this for fear of killing efficiency. Gonna give it a try next time and see how it goes! :mug:
 

Gavin C

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hmm, I've always been scared to try this for fear of killing efficiency. Gonna give it a try next time and see how it goes! :mug:
I had similar fears till gradually my dough in got ever faster and faster till it became almost instantaneous. Ever since, complete shady anecdotal evidence would seem to suggest that my control of FG has improved.

Read more here if you are interested. Somewhat relevant I suppose.
 

beerisyummy

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I either don't like or have not learned to properly use the settings on my MM3 mill. I also hand crank the damn thing, because reasons. (Exercise?) My completely unscientific method is to set the rollers as close as I can, then back up until I can actually turn the crank. I get a nice fine crush with lots of flour. Seems to make decent beer. :bigmug:
 

JohnnyO'

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I did a stove top small scale test that showed you do not get much down below 0.030". Moderate gravity.
 

semize

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Forgot to mention you can use a credit card to set the gap. That will get you to a .9mm gap which should be perfect for a single pass crush.
A card will get you in the ballpark. Not all cards are the same width, and they can be different widths depending on which end you use. For example my debit card is 0.80mm on one side and 0.78mm on the other (really an insignificant difference). My credit card is 0.92mm on one end and 0.81mm on the other (just measured with calipers).

On a related note, I have issues with water / heat passing through the bag when grinding too fine (for me that's less than 1mm or 0.036in) . During a mash out the water outside the bag will heat up significantly faster than inside the bag, even with constantly stirring the bag and scraping the sides of the bag. This makes hitting 168-170 for 10 minutes very unreliable. I prefer to keep things a little coarse to help water, and therefore heat, to more easily flow through the bag and grain. I'm using a 200 micron "The Brew Bag". My only guess is the grind-it-to-flour folks are skipping the mash out.

Even with the larger crush size I'm still hitting 80%+ efficiencies.
 

estricklin

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I'm a fan of the old saying "Crush til your scared", and with BIAB there's really nothing to be scared of so, I would say cornmeal for me. I go a little coarser for my 3 vessel; I've had a stuck sparge or 2 in my day and don't want to relive those brew days.
 

semize

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Mash out isn't needed for BIAB nor for conventional mash tuns when batch sparging. You can save youself problems by simply eliminating this step.
Mind if I ask why?

Heat transfer is also an issue when doing stepped mashes, which I do on occasion.
 

RM-MN

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When you use a conventional mash tun you will be limited in how fine you can mill the grain and still be able to drain the tun when the mash period is over. The coarser particles of grain then do not get fully converted and the mash out stops conversion. This keeps the conversion from continuing while you would be doing a long fly sparge. With batch sparging you can drain the mash tun, add the sparge, stir, then drain again, limiting the time for further conversion. With BIAB you would likely have milled the grain much finer leading to full conversion. With no starches (or very little) left to convert it the mash doesn't need to be stopped with a mash out. Besides that, you will pull the bag of grain out and begin heating the wort which effectively becomes a mash out as you heat the wort towards the boil.

Step mashes are another situation. Probably the most effective way to do step mashes in BIAB is with decoction or possibly with a recirculating system. Are you sure you need the step mash? Many of us never bother and just do single infusion.
 

semize

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That makes sense. Although I don't understand why someone would want to stop conversion. I'm guessing if you're really set on hitting a certain pre-boil gravity and you hit it before sparging? Bit then you would dilute the wort and lower the gravity with the sparge? As a BIAB brewer I guess it doesn't matter to me, but curious none the less.

From my understanding the extra heat of a mash out decreases the viscosity of the wort, which helps it drain more thoroughly from the grain bag giving those few extra gravity points or a little extra volume (although that's probably negligible). Better to be safe and err on too much than too little? (/edit) The only reason mash out stops at 170 is because any higher temp would extract unwanted compounds from the grain(?).

/edit - probably just simpler to add an extra dollar or two of grain than try to eek out those two extra points, eh? Adjust to a slightly lower brewhouse efficiency.
 
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RM-MN

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The actual difference in the viscosity of the wort at hotter temps is hardly enough to measure. Getting the temperature over 170 is not a problem if you keep the pH of the wort down where it belongs. If that were not true, decoctions would make some awful beer as the brewer takes part of the mash and heats that to a boil before returning it to the mash to raise the temperature for the next step.

Some of us have learned that we don't need mashout nor do we need hot water for sparging. I take water right from my tap (no chlorine in it) for sparging and since the temp then is well below the 170, I don't have to worry about over sparging raising the pH enough to extract tannins as that take the higher pH and higher temp. That then allows me to triple batch sparge to get more of the sugars out without astringency. It also makes the bag of grains cooler so I can squeeze it without burning my hands.
 

semize

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Thanks for humoring me RM-MN and taking the time to answer my questions, I really appreciate it. I'm learning!

I didn't realize temperature directly impacts pH, that's good to know. I knew measuring pH at higher temp changed the reading compared to room temp, but didn't realize that also correlated to changing the effective pH of the solution. Interesting!

Doing some quick searching I'm finding that raising the temp effectively lowers the pH, which isn't ideal but doesn't contribute to tannin extraction(?).

Still, at your recommendation I'm going to skip the mash out on my next brew. Like you said, seems more pain than it's worth given all of the variables it changes. Now I'm wondering about pH during step mashes... start high at 5.5-ish and let the temp rises keep it in the ideal band? I'm looking forward to taking pH samples on the next step mash!
 

semize

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Ahh, sparging potentially dilutes the mash, which would dilute the acidity and raise the pH...
 
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