SG 1.046 to OG 1.066 ??? I'm measuring something wrong?

[odie]

Title says it all. I jumped 20 points during the boil. I do BIAB mashing. I mash "overnight" or "overwork" for 10 hours. I ended up with 6.6 gal of wort collected at 1.046. I used some different conversion calculators online with my grain bill, wort volume and SG numbers and got a range of 67-69% efficiency. I usually get upper 80s and even 90s efficiency. Something was way off. Then I finish my boil at 6.05 gal and after cooling to 100' it's 5.85 gal. My post boil OG was 1.066. that's a 20 point rise for only a 3/4 gal boil off ???

I'm guessing I must have seriously misread the hydrometer after mashing. Or miss-read my sight tube?

 

[Immocles]

I've gotten varied SG readings before. Was the sample cool enough? ( or corrected by calculation if not). My guess would be that the sample wasn't completely mixed after the mash. That could help explain both the drop in efficiency and the increase from significant SG to OG.
Was the OG close to what you had been expecting?

 

[odie]

I think it was mixed pretty well. I recirc while mashing normally but my pump died. But still after 10 hours of mash I should have had full conversion.

The OG was in the realm of what I was expecting. I pulled almost 3 lbs from my standard DIPA recipe cause my BIAB system has evolved to practically zero wort/beer waste and my ABVs were getting too high to enjoy more than 1-2 beers a sitting.

 

[Immocles]

Hmm. It’s odd to say the least. Something fluky had to have gone down with that initial reading. I’ve never come close to that type of boil off.

 

[odie]

that's my guess. I just dorked up the SG reading. No way I can gain 20 points in the boil off unless it was several hours and a couple gallons.

 

[RM-MN]

I use a refractometer to measure preboil gravity. If I measure while the bag is still in the pot and take a sample near the top it will show a low gravity. 2 inches down the gravity reading will be higher. 4 inches down, the limit of the pipette, it will be higher yet. I suspect your wort was stratified with the more sugar laded and dense wort at the bottom. I take my measurement near the end of a 30 minute mash, your reading was after 10 hours, plenty time for the sugar laden wort to stratify.