Faced with the task of constructing a tuna sandwich, my thoughts turned to choosing materials which would be accurate in texture, shape and density. The bread could easily be made from ordinary foam rubber scrimmed with muslin on the top edge and paper towel (the waffle-textured type) on the sides and bottom. For the tuna mixture, wood shavings mixed with coloured epoxy resin would do. How to realistically capture the shape and texture of lettuce proved to be the challenge.
Experimenting with various materials, I finally came upon a flexible, clear vinyl (sold as a tablecloth covering). Warming the material with a heat gun to make it pliable and stretchy, I tore it into lettuce-shaped pieces. Depending on how quickly the vinyl is torn and how close it is to the heat source, various sorts of wavy and jagged edges will appear, just like leaf lettuce. Once the piece is the right size, balling it up while still warm will capture the undulations of the lettuce leaf. I used a hot glue gun sparingly to lay out the network of veins. Working from a sample, I used artist's acrylics in washes and glazes to colour, wash and highlight the leaf.
The result was very satisfactory, as the leaf had the correct ragged, wavy edge, the right thickness, and was just translucent enough to be convincing.