[gmac]

I don't disagree with anything that's been posted here but in my own experience, I saw the best jump in efficiency when I went to a higher water:grist ratio.  I now consistently use 2L per lb of grain and went from around 74 to 82 or so on my 5 gal batches.  I have my own mill and I don't know the gap since I don't have any feeler gauges but I'd suspect it's on the tighter side based on the impact it has on the barley husks, they come out busted up but stuck sparges have not been a problem so I leave it alone. 

I bought a bigger brew kettle and am going to 15 gal batches so I haven't gotten my system dialed in perfectly yet but I usually end up with greater efficiency than I'd planned rather than lower and am currently using 80% as my guide until I get more batches done with this system.

[denny]

I have to say that the second most important variable is the runoff rate. The slower you go, the higher the efficiency. Even with batch sparging, I'd have to say that extending the duration should have a positive effect.

Martin, I can assure you that it does not.

[jrskjei]

Who didn't see that one coming from Denny?  Hilarious.  Correct.

Kind of off topic, but... I've noticed a large gravity gradient in the mash when batch sparging with a 17 gal chest cooler and stainless braid.  There's a 0.2 SG difference between the top of the mash and the bottom, even after recirculating a few quarts.  Anyone else observed this?

I've had rather poor efficiency (60%), though I don't expect the gradient is related to efficiency.  I've progressively increased the stirring of the mash, to the point where I'm losing quite a bit of heat from the mash (5 deg C over 60 min in the last brew, which was the most observed).

Also, have been using the mill at Midwest and setting it as narrow as possible.  Has anyone else been getting a poor crush at Midwest?

[denny]

Kind of off topic, but... I've noticed a large gravity gradient in the mash when batch sparging with a 17 gal chest cooler and stainless braid.  There's a 0.2 SG difference between the top of the mash and the bottom, even after recirculating a few quarts.  Anyone else observed this?

I've had rather poor efficiency (60%), though I don't expect the gradient is related to efficiency.  I've progressively increased the stirring of the mash, to the point where I'm losing quite a bit of heat from the mash (5 deg C over 60 min in the last brew, which was the most observed).

I can't say that I've noticed it, but if you batch sparge I can't imagine why it would make a difference.

[jrskjei]

I can't say that I've noticed it, but if you batch sparge I can't imagine why it would make a difference.

It became a bit of an issue when I thought I was getting 40% or so efficiency in the mash, but after I started taking gravity readings in the kettle just before the boil began, I realized that something was up and then started taking gravity readings at the top and bottom of the mash tun.  It does make it harder to troubleshoot efficiency issues since I didn't really know if I had a problem or a big problem.  It also makes it difficult to determine if the mash conversion is complete, since I was going off of gravity alone and not an iodine test or anything else.  Hopefully adjusting the crush will help with the efficiency, but it makes it difficult to know the conversion rate until the wort is in the kettle, when it's too late to make adjustments with anything but the batch sparge step.

[rabeb25]

Since you are in MN, where abouts? What water are you using? I saw bad efficiency from using tap water in the NW cities(not to mention other issues).

[jrskjei]

I'm in Eden Prairie.  The city softens the water at the treatment plant and, as far as I know, is the only city getting it's water from the Prairie du Chien-Jordan aquifer that does so.  I brew mostly light ales and darker stouts and porters, and I do adjust to generally get the lower end of the concentrations recommended by Palmer for those styles.  My water profile is:
Sodium, Na 11
Potassium, K 2
Calcium, Ca 20
Magnesium, Mg 12
Total Hardness, CaCO3 100
Sulfate, SO4-S 8
Chloride, Cl 36
Carbonate, CO3 9
Bicarbonate, HCO3 34
Total Alkalinity, CaCO3 43

Ward labs water report.