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
I typically double mill the grain, not to get a finer grist but to ensure most of the grain is crushed. I did not readjust the mill setting from the previous time I milled.
I also know that in BIAB, the grain is milled finer but I am not seeking to do that. It is more the case of not seeing the necessity to sparge as I am brewing smaller batches. I use to batch sparge and use onebeer.net’s calculator. I don’t worry either about the initial amount of wort. I have in mind the amount I want and calculate for that. This time, I wanted 5 gallons, not 6.
As Denny said about not seeing why, I am in the same boat and could not figure why.
There is no requirement for finer milling for BIAB. I don’t know where that myth came from. People assume you can mill finer because there’s not a sparge. Maybe, maybe not the reason. I don’t do no sparge BIAB, but I still mill extremely fine. And have no issues because of it.
I don’t see why top on versus top off would make any difference to the absorption. At 149F evaporation is also not a major issue.
BeerSmith 3 brewing software uses a default grain absorption value of 0.96 fl oz/oz for standard sparging and 0.586 fl oz/oz for BIAB. That is lower, but not as low as you saw. For 10 lbs = 160 oz of grain the BIAB value would be 160*0.586 = 93.76 fl oz = 0.733 gallons. That is about 3 times what you saw. The only explanation that makes sense to me is measurement error somewhere along the line.