Marking the first time the inner dome has been professionally cleaned since the Capitol was completed in 1906, more than 2,000 pounds of dirt and debris were collected and removed as a result of the dome-cleaning project. The three-phase project began in the interstitial space of the dome structural cavity — the protective steel-reinforced concrete shell located between the exterior tiled roof and interior plaster Rotunda dome — with a complete HEPA vacuum cleaning of all surfaces and a damp wipe down of all exposed structural steel components. This work was done at night from 6 pm to 4 am. The remaining two project phases were conducted in the second and first level access tunnels. Both brick and concrete passageways, which encircle the interior Rotunda dome, are virtually soundproof, allowing work to be conducted during the daytime without any impact on Capitol personnel.

Although it is hard to imagine that such a large amount of material could accumulate, it is because the interior dome acts as a giant chimney for the Capitol rotunda. Air, along with dust and dirt, rises up through the dome where it circulates through the structural cavity and access tunnels, and is eventually released through vents. Although not visible to the public, these inner cavities play an important role by helping to control temperature and humidity levels of the dome, which is crucial for structural integrity and preserving artwork in the interior dome and rotunda.

Besides dirt and dust, a number of interesting artifacts were found, most of which date back to the period when the Capitol was constructed. Some of the most substantial findings include a carved handle thought to be from an Irish shillelagh, a silver spoon, a State flag, and a copper-handled paintbrush. There are also numerous paper fragments, such as the corner of a wrapper from a Hershey chocolate bar, priced at 5¢, along with an Irish song sheet, newspaper comic strip clippings, a StarKist Tuna matchbook cover, and a full-page advertisement for a lead pencil sharpener made by K&M Manufacturing Co., just to name a few.

One of the most intriguing parts of the Committee's restoration work is the interesting artifacts and discoveries that are  made during a project. These bits and pieces of history bring the construction of the Capitol down to a personal level and often reveal something about the lives of the individuals who made the Joseph Huston's vision of our monumental state Capitol a reality.