You apply tufa mix to the backside of a leaf.
When the tufa is 'set up' you remove the leaf which is now your front. It will show the veins.....There are many threads here on how to do them, but that's it in a nutshell. My personal opinion....a 1:3 mix of port and sand works better.
Marcia

Hi Clare, I agree with Marcia, plain old Portland cement and fine sand works much better for a nice smooth finish, I also use her same measure 1-3. First make a small pile of damp sand, place a covering of plastic wrap over the sand then your leaf(start small), pat your wet cement mix onto the leaf just to the edges, then cover with another piece of plastic wrap (any brand). Let sit for 24hrs, turn the cement leaf over & remove and discard the actual leaf. Keep lightly misted and covered for about 7 days. Wear a mask while handling the dry cement, also rubber gloves, wet cement can make your hands very sore! have fun & Good luck! Wendy