I agree with Jack. I have talked with a few old time maplers and have heard the same. Maybe you don't lose a full grade but if you were leaning towards the next darker grade you would be at it upon reheating. Last year I made a higher % of lighter grade syrup and believe I did it because I had fewer but longer boils instead of 4 or 5 hrs and then shut down to reheat and add more sap. In 03 and 04 I would run a boil even if I only had 3 hrs between bus runs (I drive school bus) and then resume boiling after work until all sap was in the pan. Then I would shut down and resume on the next day of flow in the same method. In 05 I did not boil more than 1x/day and often went 2-3 days if temps permitted. In this manner I made lighter syrup. I really think it had to do with the # of times any given drop of sap was reheated before it reached the proper density. I plan to do the same way in 06.
Dave Klish, I recently ordered a 2x6 wood fired evaporator from A&A Sheet Metal which I will be converting to oil fired
Now have solar, 2x6 finish pan, 5 bank 7x7 filter press, large water jacketed bottler, and tankless water heater.
Recently bought another Gingerich RO, this one was a 125, but a second membrane was added thus is a 250, like I had.
After running a 2x3, a 2x6, 3x8 tapping from 79 taps up to 1320 all woodfired, now I'm going to a 2x6 oil fired and a 200-425 taps.