I'm going to attempt reducing a balsamic vinegar into a syrup, and while most recipes I've found recommend bringing it to just a boil and then lowering the temperature, none of them ever specify what setting I should use to bring up the initial temperature. High? Medium? It seems like it would make a big difference in how fast it reduces and perhaps even the taste. Thanks!
It really doesn’t matter. Vinegar is rather a non-viscous fluid; convection will ensure that, no matter what rate it heats at, it will heat evenly. And since it’ll be spending an extended period of time at boiling temperature, the amount of time it spends below boiling temperature isn’t going to make much of a difference.