How fine is too fine?

[Michael_K]

I've done 3 AG (half)batches so far -all BIAB- but I haven't been getting very good efficiency. Here's my process:
Mash 5-6 pounds in 2 gallons at 150-154 for 60 mins. Let drip. Dunk the bag in 2 gallons at 170 for 10 minutes. Let drip. Combine. Boil 60 minutes, yada yada yada, I get 2.5 gallons in my fermenter. But my efficiency has been lousy.

So here's my question: What if I grind my grain VERY fine - like chunky flour. No stuck sparge, 'cause BIAB, but do I need to worry about extracting tannins from the husks? We have a Bosch flour mill (with adjustable settings) that I've been eyeing for the job...

How fine is too fine for BIAB? Will I get off flavours from the shredded husks? Any other tips to improve my process? Thanks for the help!

 

[pricelessbrewing]

There's a few users that do a .010 gap on their mills. Should be just fine.

 

[number40fan]

Everyone that BIAB say you can't go small enough.

 

[Michael_K]

Thanks for the replies. I mash in my brew kettle, do I need to worry about grain flour or bits of husks getting into the boil?

 

[pricelessbrewing]

Thanks for the replies. I mash in my brew kettle, do I need to worry about grain flour or bits of husks getting into the boil?

The only time I had this happen is when my bag fell off the lip of the kettle and some spilled in, still didn't have any significant off flavors.

I use 2 curtains from IKEA folded over a bunch, so my "bag" is massive and layered multiple times. Not worried about any grains getting unfiltered.

 

[TexasWine]

Thanks for the replies. I mash in my brew kettle, do I need to worry about grain flour or bits of husks getting into the boil?

The only thing that I would be aware of is dough balls. Be prepared with a whisk. The finer you get with your grind the more dough balls are formed.

I'm one of those folks that use a 0.010 gap on my mill.

 

[soccerdad]

Is the kettle big enough to mash the full 4 gallon volume? You might to better with a full volume mash v. the half n half

 

[Michael_K]

This is good news guys, it's puts my mind to rest about off flavours - and hopefully I'll be able to bring up my efficiency.
@TexasWine, thanks for the tip, I'll have my whisk handy.
@soccerdad, not yet, I'll have to get myself a bigger kettle for Christmas - and something that I can do 5 gallon batches in!
Thanks again!