Conservation Program

Conservation Program

Services

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The Trust provides a wide range of architectural conservation services to its clients. For those not familiar with the role of architectural conservation in the preservation and maintenance of historic structures, the following is a summary of the services we provide, and how they affect the buildings you see.

Laboratory Services

It is important to remember that while each of these techniques can provide accurate information regarding a specific element or component of a building system, they must be viewed within their individual contexts. Effective treatments of buildings will consider a wide range of evidence within the light of knowledge of historic construction techniques and product availability.

Paint Analysis

One of the most common maintenance projects in all buildings, historic or modern, is painting. A new coat of paint can transform the appearance of a room, bringing it into contemporary fashion, or simply freshening up its current appearance. Over the years, the original paint schemes of buildings are frequently lost, sometimes drastically altering the appearance of the buildings.

Paint analysis is performed for many reasons, most frequently to determine the color or composition of the surface finishes present at a given period in time. However, paint analysis can also determine the type of paint and the composition of pigments used in a finish layer. This information can be used to date a finish layer, giving conservators information about the construction chronology of a building or the timing of subsequent painting campaigns. For example, the pigment Prussian Blue was invented in 1704, and therefore cannot be found in a layer predating this. Similarly, the pigment zinc white, although first suggested for use as a pigment in the late 1780s, did not come into common use in the United States until the 20th century. By using techniques like these, conservators are able to provide accurate information regarding the dates of additions, treatment of woodwork, etc.

The binder (i.e. oil, latex, etc.) of a paint layer can be determined through paint analysis as well. Special chemical stains are applied to a paint sample and observed under a microscope; different binders react to the stains differently, and their composition can be determined through these observations. Binder composition is a crucial element in treatment of existing finishes, as the binder of the paint is the component that determines its solubility and resistance to chemical attack. For example, while a commercial paint stripper is effective against latex-based paints, a milk protein-based paint may be completely resistant to it. This information is critical in designing a treatment for conserving an original finishes scheme.

The techniques of paint analysis vary little. Tiny samples are removed from the element being analyzed with a blade or hand tool, with care taken to remove all finish layers. The samples are prepared to reveal the stratigraphy of finishes, that is, all of the layers of finishes. The samples are then evaluated under a microscope using various types of filtered light and chemicals.

The photograph to the right shows the paint analysis performed on the Sedgeley Porter's House. The layer marked with an arrow dates to the period of restoration. As two wing additions were constructed between 1870 and 1899, this was chosen as the period of restoration. The indicated layer was found consistently on all of the exterior window frames, including those included in the two wing additions.

The information gathered from the paint analysis was compared to technical paint literature from the late 19th century. Based on the colors visible during paint analysis and the colors known to be available at the time, the current color palette for the building was chosen.

Mortar Analysis

Because pointing mortar (the outermost layer of mortar between stones or bricks in a masonry building) is designed to deteriorate preferentially, it needs to be replaced periodically. In doing so, however, it is imperative to replace it with a mortar that matches the original in physical character. If a replacement mortar is harder than the masonry units it bonds, it will prevent the stones or bricks from expanding and contracting naturally, and lead to a rapid rate of deterioration. Additionally, cement-based mortar can impart damaging salts to the masonry units, introducing another deterioration mechanism.

To avoid these potential dangers, conservators analyze the components of the existing mortar, and determine an appropriate replacement mortar mix. Mortars to be analyzed are placed in a small amount of dilute acid. The acid consumes the binder, usually lime-based components of the mortar, and leaves the aggregate behind. Once the binder has been digested, the conservators are able to visually analyze the aggregate, and compare the ratio of the two components. From the information gleaned throughout the process of analysis, conservators are able to design an appropriate replication mortar that matches the original in visual and physical characteristics, thereby simulating the conditions created by the original mortar. This type of analysis can also be used to determine the composition of interior and exterior plasters.

General Services

Condition Assessment

Prior to any intervention into an historic building, it is first necessary to evaluate the existing conditions and document them both visually and in writing. Current conditions are almost always the indicators of deterioration mechanisms, and it is through the identification of deterioration mechanisms that appropriate treatment recommendations are made. The Trust conservation staff frequently performs condition assessments and provides treatment recommendations for a wide range of cultural resources, from individual sculptures to historic sites with multiple structures. An example of a graphic condition assessment is shown to the right.

Wood Conservation

Unfortunately, wooden elements of buildings are frequently replaced rather than conserved. The Trust routinely advocates for the conservation of wooden building elements including window sash, shutters, doors, and sills. While old windows may seem drafty and irreparable, this is rarely the case; in fact, replacement windows often fail more quickly than repaired wooden windows. To this end, the Trust frequently undertakes wood conservation projects, including consolidation, filling, tightening of joinery, conservation of hardware, and glazing of windows with historic glass.

Masonry Repair/Repointing

The Trust provides a number of masonry related services. In addition to performing mortar analysis, the Trust repoints monuments, statues, and buildings, and repairs damage to masonry amenities caused by impact or abrasion. Repointing requires the use of replacement mortars, and repairs involve using specially designed mortars. The Trust also removes graffiti from historic buildings and monuments. Normal graffiti removal techniques involve high-pressure washing and caustic chemicals. As historic structures and sculpture are often constructed of more sensitive materials, these methods frequently do more damage than good, removing not only the graffiti but also the surface of the masonry. The Trust takes care to ensure that only the applied graffiti is removed, and the substrate is retained.