does O2 throw off refractometer reading?

[H22W]

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?

 

[Bensiff]

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.

 

[H22W]

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?