I understand that BIAB mash efficiency can be improved with small mill spacing. I’d like suggestions for best mill spacing and bag microns. Thanks.
For my personal needs and use case, I have my Monster Mill MM2 set to a gap of .035 inches. I’ve tried bigger and smaller, and this setting hits best on the intersection between efficiency and draining well during recirculation and after pulling the mash bag.
I brew using an Anvil Foundry 10.5, so BIAB with recirculation. I’m not sure on the bag itself, but I see the standard ones are 400 microns. [edit - I confirmed that mine is the 400 micron version; it does well with this crush, and has lasted for close to 5 years at ~25 brews annually on average]
For a “typical” gravity of beer (1.045 to 1.055), I average around 68% mash efficiency using this setup; it can be around 70 to 72% in the low- to mid-1040’s, and lower (<68%) as I get to higher gravities.
As for what’s “best” – that’s something you’ll have to iterate towards. Some folks are OK wherever they land, and some aren’t happy unless they are in the high 70’s for efficiency (note: I’m often skeptical of high mash efficiency numbers, especially for BIAB – it’s like farmers comparing bushels per acre or anglers comparing fish length; often susceptible to a dose of exaggeration and posturing). For my part, I like 68% mash efficiency because it is predictable for most of the beers I brew, and I can anticipate predictable variations for low gravity or high gravity beers.
The only way to really know is to pick a setting and try it.
I have always just set my mill at the narrowest gap setting: .025. But I don’t recirculate or anything like that.
My brew bag is 250 micron nylon mesh.
My efficiency is negatively correlated with OG, but for moderate strength recipes, I can usually count on efficiency in the 70s.
1 Like
Thanks Andy. .035 gap and 400 microns gives me a starting point for my iterations. I see that https://www.brewinabag.com offers bags ranging from 200 to 800 microns.
1 Like
I use a brewinabag.com 200 micron bag. I am not sure what my mill gap is. I think I started at 40 mils and went down until I was happy with my filtration and efficiency.
PS. I don’t recirculate or sparge. I just mash and drain with a pulley also purchased at brewinabag.com, old school BIAB style.
1 Like
I grind to about 0.026" and get mash efficiencies of around 83%. If you want to recirculate you will need a coarser mesh bag, like 800 microns, that will let some particles through if you crush finely. If you try to recirculate with a tighter mesh you will get compacted grain at the bottom of your bag and not enough liquid flow.
Unfortunately, the guy I got my bag from 12 years ago isn’t in business any more, so I’m just guessing about my mesh size. I think it’s 200 micron, but I’m not 100% on that. My mill gap is roughly 0.035" - I use a 0.88mm Tortex guitar pick as my feeler gauge.
I use a (Mike) Wilser Bag from (Bobby) BrewHardware: Wilser Mesh BIAB Bag for 10-11 gallon Pots
I set my JSP Malt Mill to the width of my debit card.