flue/sap flow question

[jimbo752]

Im sure this has been explained multiple times on this site, but i cant find it so ill ask- From what i think i understand the sap at the bottom of the flues has less sugar content than at the top, so the higher sugar content sap flows through the pan and doesnt end up in the bottom of the flues. is this correct, and if so what causes this, and is it just a function of the heat in the pan- does the higher sugar content sap go to the bottom when your not boiling. Sorry to bug people with the question but i cant find the answers anywhere.
Thanks

[RileySugarbush]

If you have ever looked into a boiling flue pan it will be clear that the sap is completely mixed by the violent boiling. On average the sap will be lower sugar content near the float and higher near the outlet to the syrup pan, but there can be no gradient vertically, there is just too much mixing going on.