does O2 throw off refractometer reading?

I got an unexpectedly low reading on my refractometer that I would like to reconcile.

This was my first attempt at a partial boil. I started with approx 11.5 lbs LME in an 8 gallon kettle.

About 5 or 6 gallons of wort into the fermenter. Refractometer read 1.086 which seemed about right.

Then I topped up with water to about 11 gallons (total) and oxygenated with O2 stone.

Then I took multiple refractometer readings even shook the fermenter a bit and all readings were 1.026.

I was expecting 1.035 to 1.040, what happened??? Did the O2 throw off the refractometer or maybe my shaking just hadn't mixed up well?

 

Unless you had actual air bubbles between the prism and cover, no...you probably just over diluted as it sounds like you are uncertain. But, do a hydrometer reading, I find that refractometers can be tempermental especially cheap ones.

 

Yes, I had so much foam in the fermenter all my attempts did have bubbles on the prism. So, bubbles on the refractometer glass is no good?