Wort stratification in mash

[MattGuk]

Hi all,

Just a quick one, when mashing I assume when taking a sample for a refractometer reading from the top of the mash ( full volume ) the concentration of sugars at the top will be weaker thus giving a lower reading?
Might sound obvious, but I'm not 100% sure.

 

[Agentgonzo]

Hi all,

Just a quick one, when mashing I assume when taking a sample for a refractometer reading from the top of the mash ( full volume ) the concentration of sugars at the top will be weaker thus giving a lower reading?
Might sound obvious, but I'm not 100% sure.

Assuming you don't have clear wort sat above the level of the grain bed, the concentration of sugars should be the same throughout the mash.

If you're doing a full volume mash I would expect there to be wort above the level of the grain bed. If you don't mix/recirculate then I'd assume the top wort would be more dilute

 

[Rwilts]

I generally take my wort for a reading from the recirculation outlet

 

[MattGuk]

sorry for the late reply.
I brew in a BrewMonk all in 1 and do recirculate through the entirety of the mash, albeit a very slow trickle, but I I stir from time to time throughout the mash, I then take a reading from the clear wort at the top of the mash, but it's odd because my last brew I measured a preboil gravity of 1.044 but my post boil gravity was also the same, even though I had 3.5 ltr boil off, samples were both cooled to 20°c.
this always seems to be the case that both pre and post boil gravity's are pretty much identical.
I'm just wondering if it's not mixing enough to give an accurate reading.

 

[Caramel Ox]

I have definitely seen that the mash will stratify- I take pre boil gravity when it is about to boil. If done earlier I would expect to have to stir well enough to vertically mix it.

Previously I would check mash progress a lot but you build confidence over time.

 

[MattGuk]

I think maybe I'll do that in future, take a pre boil gravity when it's close to boiling point, because I have no idea which reading is correct, as both end up being the same more often than not which I know sounds crazy.
I'm guessing my pre boil isn't mixed enough and I'm measuring a higher more concentrated gravity, although, I'd have thought the higher gravity wort would be at the bottom and not the top.

 

[The-Engineer-That-Brews]

Wort can definitely stratify: after the boil I notice the more sugary (denser) part sinks fairly quickly to the bottom.
Well worth giving it a good 'top to bottom' stir before taking an OG reading.