“Use of Waterjetting In Conservation of Historic Structures”

The Society for Protective Coatings and Painting & Decorating Contractors of America (SSPC) Presentation for PACE 2005 Expo, January 23-26, 2005, Las Vegas, Nevada.

Speakers: Joseph Sembrat
Authors: Joseph Sembrat, Patty Miller

ABSTRACT

Water, steam, and waterjetting have long been used in the conservation of historic artifacts and structures such as the R.M.S. Titanic and the Saturn V Rocket at Johnson Space Center.  Integral to the conservation is the removal of loose material, reduction in salts and corrosion, retention of coatings and desirable patina, and repair of damaged areas.

Introduction:
Philosophy of Conservation and Preservation Compared to Best Practices of Corrosion Control and Painting-

The conservation of historic artifacts and structures can be more challenging than industrial refurbishing and repainting.  Even though the performance and lifetime expectancy of treatments is always high, the conservator’s approach is often constrained to the use of low-impact, removable materials such as waxes or very thin conversion coatings as compared to high performance coating systems.  The amount of attention to detail and handwork necessary to accomplish such varied tasks as removal of salts, cathodic protection, extermination of microbial induced corrosion, and rebuilding of marble is astounding, and all in a day’s work.

Conservation of historic artifacts and structures requires a delicate balance between surface preparation, with its technical aspects of surface profile, visible cleanliness, and non-visible cleanliness, with issues relating to safety and health, environmental (waste minimization and pollution prevention), and economic concerns.

All of the above impacts directly on the concerns of the conservator.  It is the conservator who must balance the decision to clean down to bare substrate and repaint, a relatively straight forward process, with the need to preserve as much of the history and structure, i.e., patina, as possible, to show some of the aging effects, and to remove for repair a minimum of historic/original material, which is not an easily defined process.

Working with historic artifacts and structures is exciting and somewhat emotional. As people walk around Saturn V, they can’t help but think of Kennedy and Johnson, the missions to the moon and the Apollo fire.  This Saturn V is the last of its kind, unique, and won’t be rebuilt. It shows the physical effects of sitting in the field at Johnson Space Center, Houston, exposed to 30 years of weather and sunlight.

The conservator must have a greater vision than simply repainting. It is often easier to make a structure look like new, than to conserve the effects of age. Thus, the conservator calls in experts from many fields and listens to what they have to say in order to come up with a balanced approach to treatment. This methodology pays off when people come to view the historic artifact and are reminded of all the events associated with the icon, including its hard fought battle with the elements and time.

The conservator’s consideration of all historic artifacts and structures involves examination, preservation, and repair.   The conservator may recommend a specific treatment(s), but the ultimate decision is placed in the hands of the client and the client’s conservation consultant. The goals of the conservation treatment are ones that emphasize minimal intervention by using the least aggressive means possible to achieve the most successful conservation results.

The projects chosen for this SSPC paper illustrate the use of water in the course of conserving a variety of substrates.  With respect to waterjetting, the projects will progress from water misting (minimal pressure) up to ultra-high pressure waterjetting (UHP WJ). An array of materials will be discussed as being treated with these techniques, including marble, granite, bronze, steel and aluminum.

It is too lengthy to go into the choices of techniques for each project. Where the industrial contractor may use abrasive blasting or grinding, the conservator will use water misting or paint stripper, followed by hand cleaning with flexible brushes. This industrial audience should keep in mind that the conservator will keep intact the original materials as much as possible and make repairs as transparent as possible. Every minute detail is described distinctly.  As a comparison, the industrial audience should think about what would happen in our industry if the contractor’s response to a bid had, each and every time, to justify the use not only of the abrasive, but also the size, shape, and operating parameters of the equipment to the specifier.