2022 Theses Master's

Leaf-Induced Damage to Finishes for Outdoor Bronze Sculpture

Clemente, Jonathan

In wooded locations, leaf accumulation on bronze sculpture is not uncommon. Leaves are very complex natural materials, with variable chemical compositions. When they sit on bronze surfaces for prolonged periods of time, they may retain moisture, decompose, release organic compounds, and encourage localized microbiological growth.

In order to study the relationship between leaves and the finishes commonly used on outdoor bronze, 16 coupons (of an alloy similar to those that were used historically for outdoor sculpture) were patinated with Birchwood Casey M-38 Antique Brown solution. Four of these coupons were left uncoated with a patina (patina-only), another four were treated with a microcrystalline wax coating (patina/wax), four more were given an acrylic clear coating (patina/lacquer), and four received a combination of acrylic and wax coatings (patina/lacquer/wax).

Each coupon was partially immersed in either a leaf paste—prepared from three different types of leaves--or rainwater for several weeks. After only two days, patina-only coupons within leaf pastes showed significant loss of patina. The coated coupons within the leaf paste also showed signs of failure and patina loss after several weeks. More research into the cause of this deterioration and the specific compounds affecting the coatings is needed. These tests merely confirm that leaves can cause an effect that is more pronounced than the effect of rainwater alone.