Iowa Old Capitol Building Case History Video

When the dome of the Old Capitol building began showing wear and tear from exposure to the extreme Midwest weather, it was critical that the existing gold leaf be removed and replaced without damaging the copper substrate. 

“Working on a historical building with a copper dome meant we had to minimize potential warping of the substrate while still achieving an anchor profile for the gold application,” said Bill Hansen of Allen Blasting and Coating. “Blasting with sponge media made the most sense for this job. It was gentle enough for use on the substrate, but removed all the existing layers of primer, sizing and gilding on the 550ft² (50m²) dome and left the specified 1 to 2 mil (50 micron) profile,” continued Hansen. 

The project began in the summer and was completed well before the university’s more than 33,000 students returned to campus. The sponge media blasting was effective and efficient, taking 17 hours, with a production rate of .5ft² per minute (2.4m² per hour) to remove the old gold leaf, sizing, and a solid metallic lead layer, while creating a profile on the copper base layer of the dome for the new coating.

Sponge-Jet’s Iowa-based Regional Manager, Cliff Mohling laughed when he said, "I had to swallow my UNI Panther Pride but having witnessed the fire that originally destroyed the dome, I was excited and humbled to be able to provide a service to the architect, contractor, and the university to help preserve the iconic symbol that not only represents the university, but also the history of the great state of Iowa."

For more on this project, click here or visit https://blog.spongejet.com/restoration-old-capitol-building-at-the-university-of-iowa