Expert: Dr. Henry Boyter, Jr. - 7/6/2004

Question
Some recipes for carmelizing sugar indicate that a non-ferrous skillet should be used.  Why is this?  Is it possible that iron, or iron oxide will react with sugar when heated?

In trying to find an answer to these questions, I have noted that sugar processing equipment for industry is also non-ferrous.  It seems that there must be a reason not to use iron based equipment.  I have also noted in my searching that carbon acts as a catalyst when carmelizing sugar, and I know that our iron frying pan at home has a thin layer of blackened carbon on it from previously fried foods etc.., whereas our non-ferrous cookware doesn't seem to have this carbon build-up.  Maybe this has something to do with it.  Anyways, those are some additional clues which might help....

Answer
This is just a guess.  I suspect that any bits of iron will cause some of the sugar to go from a molten state (carmelized) back to crystalline.  Crystalline sugar will ruin the process.  Try it.  Take some you have made and add some small scrapping from something iron.  You could try adding small sugar or salt crystals to see if it will occur.