In recent times, I have been brewing small batches (3.5 gallons) and “no sparging” in my igloo mash tun with the lid on. In recent batches, the amount of wort varies. I typically calculate for a 5 gallon amount of wort and that was what I would wind up for my boil.
Yesterday, for 10 bounds of pilsner grain, using the batch sparge calculator I have used for years, I calculated that for 5 gallons of wort, I needed 6.25 gallons of water. Measured out the water to 6.25 gallons, heated the water to 149 degrees mashed and ended up with 6 gallons of wort. Of course, my OG was much lower.
I saw a video where for the BIAB method, to lower the grain absorption rate? Is this what I need to do even though it is a covered mash tun? The calculator use .5 pounds of grain to a quart of water.
I’ve never left the lid off the mash tun to observe whether absorption would be more or less with it on vs off.
On my system when I brew a 3.5 gal in the keg no sparge batch of avg gravity 1.048 wort, I use 8# grain, strike with 6 gal, get 4.75 gal in the kettle, boil off .75 gal at 2.8kW to end with 4 gal of wort post boil.
Because pre- post boil volume is not my highest priority, if I change the gravity by adjusting .5-1# more/less grain, I use the same strike volume and get slightly more/less pre boil volume but the .75 gal boil off is exactly the same. It’s remarkably consistent and makes planning extremely reliable. If I increase/decrease by more than 1# I will reduce/increase strike by .5 gal or so.
Maybe I am confused, but I do t see how a lid on/off would impact grain absorption
Definitely could see temperature changed lid off vs lid on and perhaps total water evaporation but to what extent you would have to measure
I have been brewing with a similar system, 10 gal Rubbermaid cooler, for a loooong time now and have always kept the lid on to maintain a constant temperature