Building restoration describes a particular treatment approach and philosophy within the field of architectural conservation. According the U.S. Secretary of Interior's standards, restoration is defined "as the act or process of accurately depicting the form, features, and character of a property as it appeared at a particular period of time by means of the removal of features from other periods in its history and reconstruction of missing features from the restoration period."[1]
In the field of historic preservation, building restoration can refer to the action or process of accurately revealing, recovering or representing the state of a historic building, as it appeared at a particular period in its history, while protecting its heritage value. Work is often performed to reverse decay, or alterations made to the building after its initial construction. A part of heritage restoration can involve the replacement of outdated heating and cooling systems with newer ones, or the installation of climate controls that never existed at the time of building. Tsarskoye Selo, the complex of former royal palaces outside St Petersburg in Russia are an example of this sort of work. Physical materials of an earlier time, that might have been state of the art at the time of construction, might have failed and now need replacement with contemporary better functioning, but aesthetically similar materials. Restoration of buildings at the Bauhaus in Dessau, Germany corrected a failed c. 1925 peat composition roof.
Exterior and interior paint colors present similar problems over time. Air pollution, acid rain, and sun take a toll, and often many layers of non-original paints are applied before an attempt at restoration is made. Color spectrum analysis of old paint now allows a corresponding chemical recipe to be produced. But this is often only a beginning as many of the original materials are either unstable or in many cases environmentally unsound. Many eighteenth century greens were made with arsenic, a material no longer allowed in paints. Another problem occurs when the original pigment came from a material no longer available. In the early to mid-19th century ground mummy parts were used in making some browns.
In this case organizations like Britain's National Trust for Places of Historic Interest or Natural Beauty will work with a historic paint color recreator like Farrow and Ball to replicate the antique color in durable, stable, and environmentally safe materials. In the United States the National Trust for Historic Preservation works similarly with Fine Paints of Europe a small manufacturer located in the US state of Vermont that uses mostly Dutch and Swedish pigments and binders. The polychrome painted interiors of the Vermont State House and Boston Public Library are examples of this type of heritage restoration.