1.st post from Finnish lurker
, my 2 cents:
If you squeeze grain bag you waste less wort in grains.
That means that you can use less water overall and still get amount of pre boil wort you want.
Because you can use less water, wort is less diluted and SG is higher, and that means you can use little bit less grains to get same SG than without squeezing, and you get efficieny gain !
Squeezing works same way than batch sparging. When you do batch sparge you dilute wort that is remaining in grains, so you waste less of it. When you squeeze, the wort remaining in grains is still stronger stuff, but you waste much less of it.
EDIT: I noticed that by squeezing I actually do not mean really "squeezing" , but letting wort drip out of bag somehow. I have not actually measured how much more wort is removed from grains if I really squeeze bag vs I just let it hang and drip slowly on top of kettle.
Here Iam mashing 5gal's of 1.100 Barley Wine, total efficiency according to Beersmith2 was 70%, it is enough for me, did not do batch sparge :
Brew kettle (50l) has 3000w custom made immersion element and it is controlled with arduino based control box. Software is home made (Iam SW engineer), DS18S20 digital temperature sensor monitoring wort temperature and cheap chinese pump doing wort circulation. Out of picture is winch which Iam using to lift grain bag out of kettle. Iam very happy with this setup, works excellently.