Yes, I know that it's technically not possible for a true solution to have stratification of the dissolved solids, as the essence of dissolution is a regular and equal amount of the dissolved solid throughout the liquid, regardless of where in the liquid a sample is drawn, but empirical data leads me to suspect that with hot wort, something is going on. I constantly get low hydrometer readings out of the boil kettle before boiling unless I seriously agitate the wort before taking a hydrometer sample. It can sometimes bump up my hydrometer reading by 5 or 6 points. Why is that?
Are temperature differentials to blame? Can hotter wort carry more suspended sugar than cooler wort? And, given the volume of wort, the shape of the container, and its approximate temperature is it possible to take a sample from the top of the brew kettle and correct for the effect of uneven distribution of sugars throughout the liquid?
I only ask because I keep forgetting to agitate before taking my SG, and then I get all bent out of shape when I realize the gravity is 5 points too low, and then it dawns on me during the boil that I never agitated, and then I take a sample during the boil. Most recently I cracked a class measuring cup doing that, but it proved that, after the boil had been underway for about 15 minutes, my SG was 6 points higher.
Before anyone goes there, I cooled all samples to 59F, the calibration temp for my hydrometer, and the same hydrometer was used for both readings. Yes, I am sure I took the sample correctly. Also, it was indeed an all-grain recipe, I know this is kind of a known issue with extracts.
Is stratification of dissolved sugars a possibility in wort, perhaps owing to temperature stratification or some other phenomenon? Or is my hydrometer making this **** up and laughing at me behind my back?
I'd love to hear informed opinions and some people with similar or different experiences.