Volume 10, Number 1, Jan. 1988, pp.2-4

The Museum Climatology and Visitor Use Study Project at Hearst Castle

by Joan Samuels and Nathan Stolow

In August of 1985 the Museum Climatology and Visitor Use Study Project was undertaken at the Hearst San Simeon State Historical Monument. The project was headed by Dr. Nathan Stolow. Betty Engle and Joan Samuels from Balboa Art Conservation Center provided supervision and expertise due to their familiarity with the collection. Staff members at Hearst carried out the daily procedures. The duration of the project was approximately 1-1/2, years including a 1 year period of monitoring the environment. Four quarterly progress reports were submitted as well as a comprehensive final report with conclusions and recommendations.

As stated in the contract, the purpose of the study was: "... to conduct a scientific study to document the interaction of the climatic background, environmental factors, inherent condition of the buildings and museum collections and the ramifications of current visitor use levels at Hearst ... and prepare a report with recommendations..."

The size and complexity of San Simeon dictated that the study encompass a multitude of problems to be sorted out and solved, yet the findings were arrived at by the use of basic techniques required for any comprehensive climatology study: monitoring light levels, temperature and relative humidity and the interaction of these factors with visitor use.

There are four buildings at the site. The main building, or Casa Grande, is of solid, massive concrete and limestone construction. There are three smaller guest houses. The houses are situated approximately 1600 feet above the sea on the central California coast. The climate is changeable, ranging from hot and dry weather, typical of the hills to the east, to foggy and damp. Violent winter storms are the norm, sometimes accompanied by loss of power, broken windows, and water leaks. Winter night frosts are not uncommon, though the days are usually warm. The prominent hilltop seems to have a microclimate of its own.

The visitation is heavy. More than 17,000,000 people have visited Hearst Castle since it opened to the public in 1958. On a peak summer day there may be 5400 visitors. All are restricted to tours, but the groups may be so closely timed that for popular locations, as one group exits, the next enters. At best, the doors are constantly being opened and closed allowing the weather to penetrate. Despite careful attention of the tour guides, the doors often stay open.

With the exception of the New Wing of the Casa Grande, which was added in the 1930s and has central heating, the temperature is maintained throughout the buildings by electric wall heaters supplemented by approximately 150 portable units. The humidity is similarly regulated by 55 portable, manually operated humidifiers and 30 dehumidifiers. Cooling is achieved by the use of 150 electric fans and opening windows. The operation is at the discretion of the custodial staff on duty at the time. Needless to say, this system is unsightly, labor intensive and erratic.

There are 666 windows at San Simeon. Ultraviolet light has been reduced throughout the site by attaching UF-3 Plexiglas to all windows. Light levels are generally controlled by closing draperies during the sunny part of the day, but this is inefficient because of the large number of windows.

The first visit included a meeting with all staff members who would be involved in the study: the custodians who carried out the daily tasks such as taking light level and temperature and humidity readings and maintaining the hygrothermographs, the housekeeping staff, the curator of the collection and the staff restoration architects. The site was surveyed and photographed, documenting problems, damage, and space that could be used for equipment and ducting.

Dr. Stolow proposed that in order to make the site more manageable, zones be created within the buildings. Areas of apparently unstable condition that could be isolated to function as individual regions were selected. For many reasons, one large system for the entire main house would be out of the question. As mentioned before, the house is of solid construction with little usable space such as hollow walls, dropped ceilings, or air vents to connect the system throughout the house. Typically the architectural features are decorative elements and cannot be altered. The terms of the will make it frustrating to carry out structural changes. Furthermore, the engineering and maintenance of such a large system would be prohibitively expensive.

Passive methods of minimizing the fluctuations in temperature and humidity by further reducing the natural light entering the rooms were also pursued. Experiments were carried out with Sol-R-Veil, a translucent shading fabric that could be used in the form of draperies, stretched on window screens or even attached directly to the glazed surface of the windows. Though the light filtering properties of this material are excellent, it proved visually unsatisfactory because it obscures the outside view which is considered to be an integral part of the viewer's experience.

Llumar, a product made by Martin Processing, was subsequently looked into. It too, has excellent light filtering properties. Simply stated, it is metalized mylar with an ultraviolet inhibitor. It is cut to size and shape and attached directly to the glass. The adhesive is water activated. It comes in a range of colors and light filtering abilities. We chose two different neutral gray films for our pilot application. The film was installed both on interior and exterior surfaces. Installed it is virtually invisible with almost no alteration of the color rendition in the rooms. The only drawback is that the installation is fairly messy, requiring large amounts of detergent/water to activate the adhesive and ensure a good bond by successive applications of the detergent mixture and pressure supplied by a squeegee, thus the exterior installation for some locations.

For the study twelve Cole-Palmer, 7-day chart, quartz battery operated hygrothermographs were purchased. These, in addition to the three THG's already at Hearst, were calibrated and placed in locations carefully selected to give an indication of the overall climate. Records were made of the maximum and minimum temperature and humidity on a daily basis. These were charted on graphs by Joan Samuels which were then evaluated by Dr. Stolow. In addition, three exterior readings were taken daily with a portable psychrometer. All of the monitoring was done with all existing climate control operations carried out in the normal way; that is, with heaters, humidifiers, dehumidifiers, fans, etc. used at the discretion of the custodial staff.

Eighteen textile fade strips were placed in locations where bright natural light shone directly on objects. The cards were shielded from light on the right vertical half and two unexposed cards were stored as references for later comparison with the exposed cards. Light level readings were taken once a week at these locations with a Gossen Foot Candle Meter. The cards were collected after five months and evaluated.

Tracking of stresses and strains in polychromed wood and wood objects was carried out by measuring the space between pins carefully inserted at right angles on either side of existing cracks. The measurements were taken with vernier calipers (accurate to 0.02 mm) when the THG charts were read. A standard reference block of wood with no cracks was placed near a statue that was being tracked. The purpose was to determine whether the environmental changes in temperature and humidity are causing the wooden objects to expand and contract.

This was done in conjunction with tracking the condition of objects previously treated at BACC. The recurrence of flaking and cleavage would indicate that the objects were being materially affected by an adverse climate.

In brief, it was recommended that Hearst continue to collect data from the THG's and take light level readings. Most importantly, it was recommended that a staff conservation technician be hired to carry out the readings, maintain the environmental monitoring equipment, keep records and be responsible for the manually operated climate control equipment.

It was also recommended that Llumar film be installed in 150 critical windows to reduce the total light entering the rooms thus minimizing the fluctuations in temperature and relative humidity. Furthermore, that they have engineers and architects plan, design and eventually install zone climate control in one of the areas studied. The guest house known as "A House" was suggested because it has the most usable space for ducting and equipment. This zone should be studied before further climate controls are installed at the site.

Joan Samuels
Paintings Conservator
Balboa Art Conservation Center


Dr. Nathan Stolow
Conservation Consultant
Williamsburg, VA.

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