The materials are quite simple: crayons, paper (we experimented with all kinds, but text weight seemed to work best), an iron, acrylic paint, water, paintbrush, sponge, wax paper or newspaper, and some scrap paper.
I documented the process with my friend Karen's piece. (Thanks, Karen!) Here are the steps:
STEP 1: Draw a picture or design and color in the entire surface of the paper very densely so none of the paper shows through. (Although I did leave areas white and really liked the effect. Try both!)
STEP 2: To crack the surface, wad the paper into a tight ball, then unfurl it.
STEP 3: Brush a thinned coat of paint over the entire surface. Do not let paint dry.
STEP 4: Lay the piece on top of wax paper (or newspaper), and sponge the paint off the crayon. We laid our pieces out on newspaper and let them dry before proceeding to Step 5.