OG measurement

[yog]

I have noticed a large discrepancy between OG readings taken from top and bottom of FV on transfer.

Yesterday brewed beer with target of 1042 and og difference was 12 - 1054 at bottom and 1042 at top. Looks tastes and smells like my normal brew at 1042.

today I did first batch of new beer - mashed 215kg at 68C/154f and ran out 720liters. Maths says og should be 1074, however reading at bottom was 1084 and at top was 1064. I usually have a fair bit of trub carryover, but this is a large discrepancy, beer was a lot dirtier at bottom than top.

Which reading should i use for my s.g?

Ideas anyone?

[Jephro]

Are you measuring with a Hydrometer or a Refrac? I have noticed that until dissolved oxygen gasses off of my sample my Hydrometer will read low-> possibly an issue with different DO levels on the top and bottom of you FV. Trub could potentially throw off a hydrometer reading too.

I usually take my sample off the zwickel just before the KO is finished. My theory is that the wort is still mixing at that point and should be a homogenous mixture. I have noticed that the gravity changes (+ .2-.3°P) from the beginning of the KO to the end because the hot wort is still gassing off water vapor-> that could account for a bit of a lower reading on top; if the wort is not really homogenous and in fact "layers" in the FV.

Have you tried retesting you samples 30 min, 60 min, 90 min after KO allowing some time for mixture? Or testing straight from the kettle or transfer line during KO?