You’re welcome. That’s what we are here for.
I just had to brew a doppelbock at 1.3 qt/lb b/c I have only a 5 gal MLT. That reminded me how much more I like my 2 qt/lb standard mash thickness. 
Kai
Kai,
I presume this is a 5 gal batch size?
thanx
Yes, I updated the caption for that chart. But that only matters for the grist weight numbers that are given.
Kai
What a great topic! I have been struggling on this subject for a couple of days now. I am going to make an IPA ,10 gallon batch, using 25.5 pounds of grain. I only have a 10 gallon MLT, I figure using 1.15 Qt. per pound I can fit it in. I have never mashed so thick before and have been wondering if it would have any effect. Thanks for the great info!
I am looking at expanding my brewing to 26 gallon batches. This topic in conjunction with John Palmers website:
Appendix D - Building a Mash/Lauter Tun
D.3 Sizing the Tun
http://www.howtobrew.com/appendices/appendixD-3.html
have given me the confidence to go ahead and purchase the 120 qt cooler.
http://www.walmart.com/ip/Coleman-Xtreme-120-Quart-Cooler/14574678?findingMethod=rr
I kept second guessing about using such a large Lauter Tun, although I feel better now.
Excellent topic! As one who is about to do his inaugural AG batch I have been plowing through the literature and finding some broad ranges of answers on the subject.
So after all this I have come to the following conclusion:
Marginal differences may or may not be achieved by micro managing the ratio, but major losses WILL be incurred with clumping lumping and channeling. When in doubt, go thinner.
This may be over simplified and crude, but as a noob I have to keep it simple. When I reach master status and get bored down the line I’ll start using a pipet. ;D
Kai…I interperet your runoff chart to show that equal runoffs produce the best efficiency. right?
The other interesting thing I am thinking about is fermentability. I have always understood that the mash temp was the determining factor in fermentability but there are some great minds that believe otherwise as Kai had quoted several posts back. Thicker vs. thinner mashes may also be a factor. I wonder what mechanism can cause this?
From a pratical standpoint, I have been targeting 1.25-1.5qt/lb and equal runoffs between the first runnings and the sparge. Using this practice I have found my efficency to trend upwards.
Yes, that is correct.
This should answer this question. Here is the paragraph that matters:
The amylase enzymes are more stable in thicker mashes (Figure 8). Which is especially important to the more heat liable β-amylase and as a result thicker mashes give more fermentable worts than thinner mashes when mashing at high mashing temperatures [Briggs, 2004]. But while thick mashes offer better protection for the enzymes, they also inhibit the enzymatic activity through the reduced availability of free water and the sugars acting as competitive inhibitors [Briggs, 2004]. In addition to that the gelatinization of starch is also slower and happens at higher temperatures in thick mashes and as a result thinner mashes are known to give more fermentable worts at normal mashing temperatures.
Kai
Does a large false bottom space in a mash tun affect the grain to water ratio and lauter efficiency? I use a HERMS system, but typically don’t start my pump until the mash is well underway - if not complete. I use the old 1.25 qt/lb ratio, but my dead space (1.2 gal) is large enough that my strike temp calculations assume a 1.5 qt/lb ratio.
But anything between 30-70% batch sparge ratio gives only 1% less efficiency. Not anything to worry abuot.
Agreed. I find that if I’m within a gal. or so there’s not enough difference to matter.
Remind me again how much water is absorbed by the grain/lb ?
For me it runs about .12 gal./lb.
I did a quick search and found Ray Daniels uses .20gal/lb and this other guy named Denny Conn uses .10gal/lb. ;D
This is a pretty nifty calculator.
I didn’t want to complicate the discussion, but there is apparent and true wort absorption.
Apparent wort absorption is what you get when you neglect the volume that is contributed by the dissolved sugars. In most cases this number seems to be around 0.12 gal/lb. Apparent wort absorption is used when you want to calculate the amount of water you’ll need. True wort absorption considers that the dissolved sugars increase the volume and it will give you the actual volume that is held back in the grain. You’ll need that volume when you want to estimate the efficiency for no-sparge or batch sparge brewing. That number tends to be around 0.18-0.20 gal/lb which is where Ray may have gotten the number from. But unless he considers the volume from the sugars he will overestimate the amount of water needed for brewing.
Here is a bit longer write-up: True v.s apparent grain absorption.
Kai
I mash in a 50 qt cooler.
With my setup I lose .14 gal/pound.