I wrote a while back about my recipe for Raspberry Cordial, a very simple mixture of raspberries, sugar and time. In it I mentioned several times how you can tell that the mixture is still fermenting when you see bubbles in the mixture when you stir it. I couldn't really show you what it looked like then because we were at the beginning of the process. I'd like to show you now, but unfortunately I'm not a great photographer. Here is what my somewhat fuzzy close-up of the top of the mixture looks like before stirring. Perhaps you can get a better idea of what I mean about the bubbles created by fermentation by looking at this photo of what the top of the broth looks like once you have finished stirring - distinctly frothy.