I tried fresh mint, i managed to make a tea out of it (it was a "black peppermint" variety) that was the colour of weak indian/china black tea, using basically a whole plant and simmering for ages to try to get all the oils out of it. Tried it out and only got very very very very faint bit of the highlight of what I was photoing, no edgemarkings. But I was also using baking soda as a buffer not washing soda (I heard you didn't have to make it so alkaline with mint tea). Maybe if I had added vitamin c it would have worked better, along with using washing soda.