"Take three pints of water, and, having warmed it, add half a teacupful of wine. Put into this mixture a quantity of red-hot iron; allow it to stand for five or six days, when there will be a scum on the top of the mixture, which should then be poured into a small teacup and placed near a fire. When it is warm, powdered gallnuts and iron filings should be added to it, and the whole should be warmed again. The liquid is then painted on to the teeth by means of a soft feather brush, with more powdered gallnuts and iron, and, after several applications, the desired colour will be obtained." (Mitford 203)
Imagine if blackened teeth suddenly became a "new" instagram trend. There would have to be something appealing, like also glowing blue from a black light.