Tried to reheat maple syrup and turbinado sugar that had already been melted and reduced and it hardened. Would like to understand why.
You mixed maple syrup and turbinado sugar, heated and dissolved the sugar, then reduced it? Once it cooled it then solidified? I'm suspecting you had a supersaturated solution which is not a very stable product. Once it started to cool, especially if there was any disturbance the crystals came out of solution. Both turbinado sugar and maple syrups are primarily composed of sucrose, so I wonder if adding a bit of lemon juice or cream of tartar to the mix would help prevent crystallization.
You science-y thing you :-) I would probably try bashing it to bits, adding water, and reheating. And that would probably fail.
Did you stir it? I would guess that this is classic sugar crystalization as described by Alton Brown in "Citizen Cane"
A bit of tartaric acid dissolved in an equal amount of water would be my suggestion, also. Maple syrup is an invert sugar, so it is naturally a bit acidic, but if you're going to add a crystalline sugar, I suspect you need to bump the acid component. The amount is relative to the amount of maple and turbinado you have. For an amount equal to, say, a couple of fluid cups, go with about 1/8 teaspoon of tartaric acid dissolved in the same amount of water.
The acid functions as an "interfering agent", causing sugar molecules to spin around like bumper cars with their "like" poles trying to match up, and therefore preventing re-crystallization because the opposite poles literally can't match up and grab onto each other.
My understanding of it is a bit different. The acid causes the sucrose molecules to break into fructose and glucose molecules (1 sucrose molecule = 1 glucose molecule + 1 fructose molecule.) Sucrose alone likes to form a crystalline matrix; the other molecules make it harder for the sucrose molecules to link up by being in the way.
Wow, hla, what a beautiful explanation. I was unaware of the breakdown of sucrose into glucose and fructose. Am I correct, though, in understanding that the "being in the way" part is due to like molecular poles of sucrose and its fondness for returning to a crystalline state being forced to attempt to bond, and therefore interfering with re-crystallization? Thanks so much for such a lucid explanation.
Sorry, b, you're beyond my understanding of the chemistry of it. I know the sucrose molecules like to stack up and fit together nicely, and the glucose and fructose molecules get in the way of doing so. I'd assume there is some electromagnetic-type reason going on, I just don't know for sure...
Update: We added a little bit of water and gently reheated it, and that seemed to mostly do the trick. I think the stirring upon initial reheating was the issue. Thanks, everyone, for your input!
Glad it worked out for you!
I think you're right, Merrill. The interfering action of the acid inherently present in the invert sugar essentially causes the solution to "stir itself." Additional stirring with a foreign agent (i.e. a spoon) only makes a good situation, well, not good.