Painting conservation is the multidisciplinary and skilled technical practice of conserving and restoring paintings comprising the three core specialisms of easel painting conservation, wall painting conservation and the conservation of works on paper. Skills, technical approach, relevant scientific knowledge and ethical considerations vary across the specialisms, which each tend to have distinct training programmes and practice groups. Painting conservators recruit knowledge and skills from fields including art history, fine art, analytical chemistry, physics and environmental science. The process of restoring a painting may, in some instances, return its appearance to a likely original state, as intended by the artist when it was first created. However, in reality, remediating restoration treatments and conservation techniques achieve a spectrum of possible outcomes appropriate to the nature of the damage and deterioration, the fabric and materials of the artwork, historical period and ethical factors. A broad range of treatments can be carried out on easel paintings including the structural repair of canvas that has been torn or degraded by ageing the removal of dirt, cleaning of discoloured varnishes and the infilling and in-painting (or retouching) paint losses. A preventive conservation approach may also be taken, involving secondary protective measures such as installing moisture barriers to the reverse of frames, UV light protective glazing or stretcher bar linings, to protect paintings from further deterioration.