oh ladies...I taught a class on making caramels at the library. And just made 3 (well actually 4, but I tossed one) batches to use up my heavy cream before storm hit (in case electricity went out.)
monj, I don't use any acid...or wash down the sides of the pot, or cover it to make steam. I understand how all of those might help but the BIG change I made and that keeps me making caramel, is to portion out the sugar. By that I mean, my recipe calls for 2 cups of sugar, but using an anodized Calphalon pot & a silicon spatula, I only add 1/4 of the sugar at a time. As I explained to the class, as you start to heat the sugar, the only source of heat is the bottom of the pot. But as that sugar starts to melt, its temperature rises considerably. Melted sugar is 350 degrees...which I stress in class will TAKE OFF FLESH. So no kids, no pets, no phone, no walking away during this time. And you don't need to melt it completely (and by completely, I mean the opaque sugar is now dark and translucent). When it's about 2/3 melted, add the second 1/4 portion of sugar. But now you have the heat from the bottom of the pot PLUS that liquified 350 degree melted sugar helping the new batch to melt faster. So each step of adding 1/4 of the sugar goes quicker each time. The last portioning is where you ensure all the granules are melted completely. This end of the caramelization process will determine the color and taste of the final product.
This was where I messed up that first batch of caramel. I wasn't paying enough attention...the heat was too high and the caramel got too dark. I still went ahead and finished off the recipe (adding the liquids (heavy cream + Karo) and then butter), but the final caramel was just too bitter for my personal taste.
Anyway, to get the idea down before making caramel candy, do this step-by-step caramelized sugar part for a flan. It's the exact same idea. Use 1 cup of sugar, add 1/4 C to the pan and partially melt, then the next portion and so on. When it's all melted to the color you like, pour it into your flan pan and make the filling in the blender. Flans used to be hit and miss. Now they work perfectly every time.