The desire for dark henna goes back thousands of years. In some cultures, mainly in South Asia, it’s said that the darker a bride’s henna is, the deeper the love between her and her husband-to-be. This legend – and tales of brides being so in love that their henna turned black – prompted artists to try and replicate that effect. This eventually led people to come up with synthetic, black versions using the chemicals found in hair dye - although it's not known exactly when this happened.