I recently made nettle wine using an old recipe. Nettles (genus Urtica) are green, yet when they were boiled, as the recipe suggested, the resulting liquid was red. Why? Was this a property of the plants or of the aluminium pan, or some residue in the apparently clean pan? Nothing else, such as wine-making yeast, had been added at that stage.
• Nettle wine is normally slightly greenish-yellow, so the red coloration is probably to do with the aluminium pan. Nettles contain a substance called , which will yield a red colour when it reacts with aluminium ions released in…
