gravity off again- am I missing something ?

[SanPancho]

used to do regular biab. have switched to overnight mash in igloo cooler with biab bag and then a small batch sparge. use brewer's friend for recipe calcs. I typically saw 75 or 80% efficiency when I was doing normal biab depending on whether I did the sparge or not, double crush, etc.

but now on my last few batches I've been way off on gravity. for a 3.5gal batch in kettle, I had 6lbs grain, double crushed, with 4gals strike and .5gal sparge. collected 4gals, which is normal since I squeeze. gravity was only 33.

ph should be in the range as I shot for 5.3 via brunwater, strike should have put the temp around 153f to start. after 11 hours only down to 130f so pretty sure it stayed in conversion range for quite a while.

am I using too much strike water? can't figure out why this has happened a few times now. the only thread I can find is that I did almost-full volume. but would that take me from a 70+% efficiency down to 60%?

the very first overnight I did was 3.5gal strike, then 1.25 gal sparge, my efficiency was like 80%. no idea why this is so different from 4gals and .5 gals. don't even think I did the double crush.

I still have brewers friend set to biab, but that shouldn't make a difference should it?

im a bit stumped here.

 

[MrHadack]

In your first example it seems like your water to grain ratio is over 2.5 quarts / pound of grain. That's really thin. I'd recommend 1.5 quarts of water per pound and see if that helps.

In your second example (the very first overnight you did and got 80%), do you recall how much grain was in that recipe?

 

[SanPancho]

In your second example (the very first overnight you did and got 80%), do you recall how much grain was in that recipe?

7.5# total. 3.5gals, so like 2 per lb. thicker.

when I do normal biab there is a bit of recirculation, so I figured there'd be a bit of a drop on an overnight/non-recirc mash but only a few points, not something like 10-15%. and since its overnight, I don't stir at all either.