"Break-through", an explosion captured on paper, was printed in at least two color variations. This impression was printed in an edition of 4 on a black wove paper, using a blue background. Another variation, titled "Breakthrough" was printed on soft cream Amalfi paper with a white background, done in an edition of 11. The hyphenated title adds a nuance to the variations.
Casarella was an early practitioner of the Paper Relief print, such as this composition, starting in 1949. Using shapes cut from chipboard and illustration board he built up the surface of a plate, which was printed by hand as a relief.
By peeling, sanding, scraping and carving the cardboard elements he is able to achieve a composition that looks both spontaneous and gestural.
A description of this technique can be found on page 154 of "The Stamp of Impulse - Abstract Expressionist Prints" by David Acton, Worcester Museum, 2001.