Unexpected Low Mash Efficiency, due to new grinder or wrong water treatment?!

[Miles_1111]

Normally my mash efficiency is around 66% and the total efficiency is about 64%, however last week and I brewed a stout and efficiency fell down to 55% and 53%...! I think I did two things different from before:
1. I used a new bought electric two roller grinder instead of a hand-operated pan grinder which I used normally. Maybe it is the first time I use this two roller grinder and cannot have a better control of it?
2. I did water treatment based on distrllled water for this stout. The mash PH is 5.68 (18.1 CEL). I know it is a bit high ( should be 5.4-5.6 for stout). The minerals in the mash water are (ppm):
Cal: 131
Mag: 37
Na: 41
Sul: 136
Cl: 96
HCO3: 310
Is this PH and water bill caused the lower efficiency than usual? If not, probably the grinder. Any advice is much welcomed! Thank you.

 

[IslandLizard]

I'd look into the crush first. Proper gap width is crucial to a good crush, but which works best for you may depend on your mash/sparge system.
Are those knurled rollers? Adjustable?

I'm doing batch sparges in a mash tun without a false bottom. A gap of 0.034" works great for Barley, a bit narrower (0.025")for small kernel grain such as rye, wheat, etc.

Those doing BIAB can go finer, for a faster, complete conversion, the bag is the lauter filter.

For fly sparging a somewhat coarser grist may be needed with very little dust, so the grist remains permeable.

 

[Calder]

Really close down that gap and see what happens, don't worry if a bit of grain or husk gets thru to the boil. Even 65% seems low. If you get a significant increase in efficiency you will then know it is the crush.

 

[Miles_1111]

I'd look into the crush first. Proper gap width is crucial to a good crush, but which works best for you may depend on your mash/sparge system.
Are those knurled rollers? Adjustable?

I'm doing batch sparges in a mash tun without a false bottom. A gap of 0.034" works great for Barley, a bit narrower (0.025")for small kernel grain such as rye, wheat, etc.

Those doing BIAB can go finer, for a faster, complete conversion, the bag is the lauter filter.

For fly sparging a somewhat coarser grist may be needed with very little dust, so the grist remains permeable.

Thanks. Mine is the knurled rollers and adjustable. I will try to adjust it to 0.034" to see. I also do BIAB.

 

[Miles_1111]

Really close down that gap and see what happens, don't worry if a bit of grain or husk gets thru to the boil. Even 65% seems low. If you get a significant increase in efficiency you will then know it is the crush.

I will close down the gap this weekend and see. Will update here about the result.

 

[IslandLizard]

Thanks. Mine is the knurled rollers and adjustable. I will try to adjust it to 0.034" to see. I also do BIAB.

Many (old) credit cards (or junk cards that come in the mail) can be used as a gauge, they're around 0.034" thick.

BIAB grists can often be milled a bit finer, 0.025-28" increasing speed of conversion and mash efficiency. 75-85% mash efficiency can be expected using BIAB doing a good squeeze or drip out after lifting, or better yet, a small, 1-2 gallon dunk sparge in a spare bucket.

 

[Miles_1111]

Many (old) credit cards (or junk cards that come in the mail) can be used as a gauge, they're around 0.034" thick.

BIAB grists can often be milled a bit finer, 0.025-28" increasing speed of conversion and mash efficiency. 75-85% mash efficiency can be expected using BIAB doing a good squeeze or drip out after lifting, or better yet, a small, 1-2 gallon dunk sparge in a spare bucket.

wow, did not noticed the gap should be that small, like the thickness of a credit card! The gap of my machine is like at least 0.059" for now...

 

[RM-MN]

Thanks. Mine is the knurled rollers and adjustable. I will try to adjust it to 0.034" to see. I also do BIAB.

With BIAB you don't have to worry about a stuck mash and since the smaller you can make the grain particles the faster you get conversion and the higher the mash efficiency. Your limitation to how tight to set the mill is in making the grain go through it. Tighten that mill up. Try it with the credit card thickness. If it feeds well, tighten it some more. Some have reported a gap of .025" works for them. If your mill handles that gap well, tighten it some more.

 

[Miles_1111]

With BIAB you don't have to worry about a stuck mash and since the smaller you can make the grain particles the faster you get conversion and the higher the mash efficiency. Your limitation to how tight to set the mill is in making the grain go through it. Tighten that mill up. Try it with the credit card thickness. If it feeds well, tighten it some more. Some have reported a gap of .025" works for them. If your mill handles that gap well, tighten it some more.

Sounds a bit extreme, but I think that makes sense. I will try it. Just wondering if the gap is very small, then more powder of barley will get. Does these powder affect the beer's taste and clarity?