[denny]

Kai...I interperet your runoff chart to show that equal runoffs produce the best efficiency. right?

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.

[oscarvan]

Remind me again how much water is absorbed by the grain/lb ?

[denny]

For me it runs about .12 gal./lb.

[bluesman]

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.

This is a pretty nifty calculator.

http://www.brew365.com/mash_sparge_water_calculator.php

[Kaiser]

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

[mainebrewer]

I mash in a 50 qt cooler.
With my setup I lose .14 gal/pound.