Architecture Specialty Group Afternoon Session: Metals

The final three papers of the Architecture Specialty Group session focused on the conservation of metals. Andrzej Dajnowski, of Conservation of Sculpture and Objects Studio, discussed “Removal of Clear Coat Lacquers with Lasers.” Mr. Dajnowski used the case study of the Tadeusz Kosciuszko Monument in Chicago to show the laser cleaning process. The presentation also presented the interesting possibility that the ablation process that occurs with laser cleaning may reduce copper and tin corrosion products to their metallic states. Laser cleaning can be an effective way to remove coatings from bronze sculpture, with almost no risk of damaging the surface if properly applied.

Tami Lasseter Clare of Portland State University presented “Understanding Performance Properties and Limitations of Coatings for Metals.” Ms. Clare discussed a research project whose goal was to develop a clear coating for exterior metal surfaces with a 50 plus year expected lifetime. After reviewing traditional coatings and desired properties of durable coatings, polyvinylidene fluoride (PVDF) was selected for testing and found to have promising durability performance. Durability of PVDF clear coatings can be further increased using a corrosion inhibitor such as benzotriazole (BTA) as a pretreatment and inorganic additives that reduce water permeability.

Bob Score of Harboe Architects gave the last presentation of the ASG session. His paper, “Historic Finish Analysis and Coatings Design,” presented the restoration of the cast iron storefront of the Sullivan Center, the former Carson Pirie Scott Building in Chicago. The finishes analysis was undertaken to identify the original color scheme on the cast iron storefront. A finish analysis from a previous restoration campaign was incorporated into the current study, as well as archival documentation. The challenges and considerations related to the painting work of the present restoration project included problems enforcing required curing and drying times, surpassing the 12-month maximum duration before recoating and routine quality testing conducted by the paint manufacturer to ensure coating thickness and adhesion.