Step One:
Using a rounded scissor blade or a short metal ruler, scrap a fine layer of colored chalk dust over water in a very shallow tub large enough to hold a 12 x 18" (30 x 46 cm) sheet of paper. Repeat using two more colors.

Step Two:
Hold each end of the paper in a "U" shape and lower the center down into the water, touching the center to the water first, then letting the edges fall down slowly to prevent air bubbles.

Step Three:
Let the paper rest in the water for 10-15 seconds, then carefully lift it out of the water. You now have a beautifully marbled sky!

Step Four:
Draw horizon lines on 12 x 18" black paper. Fill the papes with the outlines of objects that will become silhouettes in the scene. Cut out silhouettes and carefully glue them to the marbled paper sky.