Renssen works with two bronze foundries to create sculptures from inception in his studio to the hand-polished finish at the foundry. Bronze sculptures require many steps over an extended period of time to arrive at the finished artwork. Renssen uses everyday objects, scrap materials and natural elements such as leaves from his garden to create new and unexpected functions in his statues. Wooden washing pins become teeth of a bull, cardboard becomes texture to a figure and a bike bell becomes a bird bath at the base of a bronze. Found objects, stone, plaster and wax are assembled to build a figure. Separate molds are then cast in liquid bronze at a temperature of over 1,100 degrees Celsius. After an extensive cooling period, the artist welds the separate elements together to create the final sculpture. Finally, Renssen selects the patina, wax finishing and color to create the exact desired result for his new creation.
In addition to bronze sculptures, Renssen works in white marble for a softer, feminine effect in delicate figure studies.