Why light at the end!!

[blissville maples]

Obviously it has a lot to do with renewing the contents of the pan but it seems like if you make 40 gallons or 140 it always seems to lighten up at the last half an hour of the boil doesnt matter if you boil for 6 hours or two hours, it always changes right at the end. If you make 40 gallons and it changes 30 gallons in how come when you make a hundred gallons it doesn't change till about 70 gallons in?? I'm baffled at this or at least that's how it seems to me

[DrTimPerkins]

It would depend on several factors....size of pan, length of time the sweet was in the pan.

Anytime sweet or syrup is exposed to oxygen (air), it will darken. The sweet in the pan darkens as it sits around until the next boil. Add fresh sap (which hasn't been exposed to oxygen very long) and the color will come up over the boil, with the last bit (probably from all fresh sap) most likely being the lightest of all.

Same thing happens in uncoated plastic containers. The syrup will start to darken immediately. The XL coated jugs (with an oxygen permeable barrier) will experience darkening at a MUCH lower rate.