Berliner OG confusion

[surgical_ass]

I soured a berliner in the boil kettle. I pitched a lacto starter culture of wlp677 and 2 cup whole grain (strained) .The post mash pre boil/pitch gravity was 1.033 ..18hrs later the ph had dropped to 3.3 with a gravity reading of 1.030 (refractometer only)

Post boil the gravity reading was 1.026 (refractometer and hydrometer) the original pre boil volume was 8 gal with a post boil volume of 6.25 gal. My boil off calculator said I should have a starting gravity of about 1.041 .

I am assuming my post sour /pre boil reading was incorrect due to alcohol being present with the hydrometer? Any ideas of whats going on? Is the post boil reading of 1.026 correct? I'm assuming it has something to do with the production of acid and possibly some alcohol?

 

[RPh_Guy]

Edit: disregard.

 

[surgical_ass]

Doesn't sound right. 26 points * 8 / 6.25 = 33 points
So 1.033 was the pre-boil gravity.

Don't trust refractometers.

That was the number I got when I checked my pre boil gravity (1.033) things got weird after I soured . after souring and boiling it was 1.026 checked with hydrometer (trusted)

 

[RPh_Guy]

Oh sorry, I spaced out completely there with the math.

Anyway...
Assuming the post-boil 1.026 is correct, then pre-boil sour s.g. was 1.020.

I have no clue why you read 1.030 on the refractometer.
Maybe you were expecting around 1.033 so you misread it 10 points higher?

At what temperature did you hold the wort while souring? The most likely occurrence is that there was a yeast contamination that fermented your wort while it was supposed to be souring.
White Labs 677 is frequently (always?) contaminated with yeast.

You'll end up with a pretty low ABV since the alcohol was boiled away. I'd suggest adding sugar to hit your intended OG.

Cheers