BIAB low OG - I am bummed....

I've done minimashes at 149 before with no effect on gravity. Well, og anyway. If you fell off more than 1 or 2 degrees, like down to 145 it may have had some adverse effects.

 

What was your grain bill? And what was the volume of post-boil wort?

 

Do you measure the amount of water pre-boil and post-boil? How long was your boil? Did you use any additional fermentables (saccharose, dextrose, fructose, glucose, etc...)? Was this a partial boil?

 

I too think the first thing to check would be your volumes. If you collected more wort than anticipated then it would lower your preboil original gravity. If your volumes are correct, then I would move on to examining the crush of your grain.

 

For a start, multiply 1 minus OG by 6 gallons, then divide by whatever volume you were expecting, then add 1. Let's say you were expecting 5 gallons...

(((1 - 1.052) * 6 gallons) / 5 gallons) + 1 = 1.062

So your volume would explain 10 points of your discrepancy (62 - 52) right there.

 

Back of the envelope, with OG of 1.052 in 6 gallons, that only about 55% efficiency for this grain bill (which I compute to 13 lbs, not 12.75). I don't do BIAB, but that sounds really low, even with a poor crush.

 

That's the best 55% of the grain though. It'll be tasty and you'll probably have a damn good drinking beer for the late spring early summer. 55% is really low, even for BIAB. I think you should be getting 65ish%, even without a sparge.

I'm not sure where you get your grain or what your crush looks like. I'd start there. If you get it from a local, I'd ask them to run it through twice. With BIAB you won't have to worry about stuck sparges.

This is a pretty aggressive crush, and exactly where you want to be after it gets out of the mill:
https://www.google.com/search?q=all...28%2Fbest-grind-setting-for-grains%2F;575;383

 

Get in the habit of doing the following measurements every time you brew, as they are the cornerstones of calculating both your mash extraction efficiency and your brewhouse efficiency:

preboil volume
preboil gravity
postboil volume
postboil gravity
volume into fermenter (batch size)

 

How long did you mash? With biab I mash for 75 minutes and get over 80% efficiency

 

Grain crush can have a dramatic influence on efficiency. I used to get premilled (LHBS) and typically got 65 to 70% mash efficiency. I now grind my own (Monster Mill), and typically get >85% efficiency. Last batch was 88%. (Not BIAB, BTW.)

 

Extending past 60 min won't really help your efficiency, but will most likely make your beer more fermentable.

Most likely culprit of your low BIAB efficiency is the grain crush, however like Koopa said above, measure the parameters above to get a better idea of where your source of efficiency loss is occurring.

One other thing worth mentioning, which may or may not make a difference... Do you have a ball valve on your kettle? If so, it would be a good idea to recirculate after you mash in to ensure the mash is well mixed (drain into pitcher, pour back over, repeat until liquid color and viscosity is consistent. The minute I started recirculating my mash liquid, my efficiency went up about 15-20% (My BIAB is around 80-85% for beers <1.080 OG; Haven't done anything bigger).

 

How do you all determine you post boil volume? Are you measuring pre-chill, or post chill? Does your volume reading include leaving the hop bags/hop spider (if you use them) still submerged in the wort?

Getting more precise measurements post boil is something I am trying to improve on. I add the immersion chiller with 15 minutes left in the boil and that adds a good deal to the volume in the kettle. Couple that with the hops in the spider and my volume reading on the sightglass is pretty warped.

If after chilling I remove the IC and hop spider, I feel I may be disturbing the sediment that hopefully coned up when I was recirculating via pump. I'd get a more accurate reading that way though.

Any advice is appreciated. Thanks!

 

I use a plate chiller so I don't have to worry about the IC inflating the volume. I also use a hop spider, but I didn't when I first started brewing so I was better able to figure out my boil off rate. Once I knew my boil off rate, then I could estimate my post boil volume pretty consistently by knowing my preboil volume, boil off rate, and boil time. Oh and when I calculate my post boil volume it is prechill so it is inflated by 4%. For example, my typical batch size is calculated as follows:

preboil volume
- boil off volume (which equals boil off rate x length of boil)
- 4% cooling loss
- whatever volume of wort I typically leave behind in the kettle/hoses/chiller
= amount of chilled wort I get into the fermenter (batch size)

 

i've done a few BIAB before i got a mashtun, the higher expected OG always ended up being lower efficiency then my mid-range OGs (with everything else being equal). Mash temp of 150 is fine and wouldn't be the reason IMO.

 

I just use the volume measurement markings on the side of my fermentation buckets Deadly accurate yo!