condition of collections to determine when an artifact requires conservation work and the services of a qualified conservator. Interventive conservation and restoration A teaching programme of interventive conservation was established in the UK at the Institute of Archaeology by Ione Gedye, which is still teaching interventive conservators today. A principal aim of a cultural conservator is to reduce the rate of deterioration of an object. Both non-interventive and interventive methodologies may be employed in pursuit of this goal. Interventive conservation refers to any direct interaction between the conservator and the material fabric of the object. Interventive actions are carried out for a variety of reasons, including aesthetic choices, stabilization needs for structural integrity, or cultural requirements for intangible continuity. Examples of interventive treatments include the removal of discolored varnish from a painting, the application of wax to a sculpture, and the washing and rebinding of a book. Ethical standards within the field require that the conservator fully justify interventive actions and carry out documentation before, during, and after the treatment. One of the guiding principles of conservation of cultural heritage has traditionally been the idea of reversibility, that all interventions with the object should be fully reversible and that the object should be able to be returned to the state in which it was prior to the conservator's intervention. Although this concept remains a guiding principle of the profession, it has been widely critiqued within the conservation profession and is now considered by many to be "a fuzzy concept." Another important principle of conservation is that all alterations should be well documented and should be clearly distinguishable from the original object. An example of a highly publicized interventive conservation effort would be the conservation work conducted on the Sistine Chapel. Example of an archaeological discovery and restoration of a mural painting Example of the restoration of an oil painting Sustainable conservation Recognising that conservation practices should not harm the environment, harm people, or contribute to global warming, the conservation-restoration profession has more recently focused on practices that reduce waste, reduce energy costs, and minimise the use of toxic or harmful solvents. A number of research projects, working groups, and other initiatives have explored how conservation can become a more environmentally sustainable profession. Sustainable conservation practices apply both to work within cultural institutions (e.g. museums, art galleries, archives, libraries, research centres and historic sites) as well as to businesses and private