Loose corrosion products were removed from the bronze surfaces using water jets at low/medium pressure in the 1,000 to 1,500 psi range with 25 in. fan tips and rotating
heads used. Most of the loose corrosion products on the bronze surfaces is water soluble copper salts; use of pressurized water provides a cleaner working environment than dry blasting and the water jets are safer for operators and pedestrians as hazardous dusts are not created. Surfaces were continually monitored to insure no bare bronze was being exposed.
Once loose corrosion was removed, the surface was inspected to determine if any original patina residue appeared. Loose pins on the bronze plaques were reset with Jahn Restorative Adhesive. The missing "O" letter was modeled and recast using the sand cast process. An alloy composed of 85% copper, 5% lead, 5% zinc was used to create the letter and finished to match the existing letters. A patination of liver of sulphur and cupric nitrate that had the same coloration as the letters was applied to the new letter. Holes were drilled in the backside of the letter and were used to attach it to the monument.
When the water jetting was completed on the sculpture, plaques, and other ornamentation, they were patinated to reduce the contrast between the areas of light green corrosion and the black sections. Liver of sulphur and cupric nitrate were the chemicals used in the patination process.
The patina chemical solution was applied to a propane-heated surface using brushes and spray units as needed to achieve the desired effect. Excess chemicals were washed off the surfaces once the proper color patina was developed.
In the absence of the City's ability to perform annual maintenance, it was determined that a protective barrier coating of Incralac would be applied to the sculpture, plaques and other ornamentation. The first coat of Incralac was applied with soft natural bristle brushes with toulene at a 50-50 ratio. The second and third coats were applied with a Binks Type 66 spray gun and the material diluted with 20% Toluene. Though all surfaces were evenly coated, extra emphasis was placed on the upper exposed areas which are subject to more deterioration than sheltered areas.
Photographic Documentation Documentation was performed prior to starting treatment and continued through completion of the project.
Continuing Maintenance Success of a conservation treatment depends upon continuing conservation or maintenance, to protect or stabilize an object. Continued maintenance of a work of art increases the longevity of the conservation treatment and reduces the need for costly future conservation treatments. The Sembrat Report identifies the criteria for proper maintenance and sets out a maintenance plan that is based upon an annual inspection of the monument.