BIAB, high OG?

I just brewed a 1 gal batch of an APA via BIAB. Full water volume to strike temp, dough in, mash, drain, boil. (added about 1-2 cups water at boil start, level was a bit low)

I'm using a refractometer for all readings (though also used a hydrometer after boil to compare)
The pre boil (with the extra water added) was 10.2 Brix (1.039 SG if my spreadsheet is right)

Post boil was 16.1 Brix and 1.066 on the hydrometer.

Beer Tools suggested it should be (about) 1.050

Final volume was about right (maybe 1/2 a beer shy)

I know most of you guys are thinking more alky? Whats the prob?
I'm concerned with missing by so much. (plus more a session drinker, so don't need the bigger beers as of yet.)

Now some random Q's
Is there a simple calc for efficiency on a BIAB?

Can one safely do a post boil dilution to get OG in check? (mainly concerned with not effecting taste, but I think its not much a prob, partial boils are done that way. But do people do partial boils with AG?)

And for you propane full boil / AG guys, how long does a 20lb tank last ya? (also state the burner BTU)

BIAB is known for high efficiency, it's not unusual to hit 80%. I'd suspect you might be even higher because of the smaller volumes you have. I set my beersmith to 78% when I'm doing BIAB.

Actually I was *just* about to edit my post.

I had Beer Tools set to 65%. (found a small calc that showed I got 82%) When I changed Beer Tools to the 82%, the OG #s fell in range.

If BIAB is this good with efficiency, I think I'm gonna stick with it.
Its a bit quicker, less to clean up, less equipment.

Whats the downside? I thought the efficiency was the downside.


(Might be common, but I run the bag inside out, that way the grist doesn't get stuck into the seams. I also made a copper ring out of left over tubing to keep the bottom stretched. First time or two without it the bag was flopping all over the place)

The downside is arguably more proteins in the beer which may lead to long term stability issues, but it's homebrew, not a commercial product. You can work out these issues with copper finings in the boil phase however just as with normal 3 Vessel systems, it's the right side of the boil that it occurs.

I had my wife make up my bag to the specs on the www.biabrewer.info website.

I'm actually getting her to make up bags for others too. Needless to say the seams are all being done on the outside.