[MUSIC] As we've talked about, a lot of aromatic faults in wine relate to sulfur. Some of them we call sulphites, and some of them we call sulphides. And I thought of an interesting way to show you the difference. Sulfites are used as a preservative in wine. Actually, many people are of the opinion that you really can't make good wine without sulfites. We've been using them for hundreds and hundreds of years. And sulfites come in the form of sulphur dioxide, either as a gas or in a powdered form that can be added to wine. And it's really, really a good thing to add sulfites to wine. But sometimes sulfites are slightly in excess. And it's when we smell them that we say that they could be called the wine fault or a borderline wine fault. Sulfides on the other hand, and I'm extenuating that word sulfides with the D. So S U L F I D E S, are completely different form of sulfur. Sulfides the most common ones that we smell, are hard boiled egg or old eggs or rotten eggs. Sometimes we can smell them in caramelized onions or garlic. Or some sulphides we smell when we have first opened a can of canned corn. And those are not very pleasant. But just as a simple illustration let me show you a simple difference between sulphites and sulphides. So sulfites, or sulphur dioxide is a combustion product between elemental sulphur and oxygen. So if I were to take a couple of wooden matches and light them. [NOISE] And forget to hold my breath [LAUGH] that pungency that explodes out towards you after you light a match is sulfites. It's elemental sulfur burning in the presence of oxygen and creating SO2 gas. And you're all familiar with that. So now you know what sulfites smell like. When you pick up a glass of wine that maybe has been recently bottled, and to which sulphur dioxide was recently added, and you say there's a little sharp pungency in there. That's probably sulfites that you're smelling. Or of course, someone could have made an error and added too many in the winery. And then you can smell that pungent smell. But here's what you do next. Take these two burnt matches and stick them in a wine glass, and put a little cover on them. And let that wine glass sit for a couple of hours, and then come back to it. So here I am, pretending that a couple of hours have elapsed. And I'm going to come back to my glass and smell them. And what do I smell. I smell a little bit of charriness. But more importantly, I smell a burnt sulphur smell. So that's no longer that burst of sulphite SO2 gas that we got when we first lit that match. This is now a lingering residual smell of burnt sulfur. Actually, sometimes people smell that at very, very low levels in wine and call it gun flint, or a flintiness, or a minerality in wine. [SOUND] But now you know what a burnt sulfur smell smells like in wine. And we can find this in wine. And it is called a reduction fault or a sulfur reduction odor fault.