Conservation and restoration of paintings

Paintings conservation laboratory, Heritage Conservation Centre, Singapore

The conservation and restoration of paintings is carried out by professional painting conservators. Paintings cover a wide range of various mediums, materials, and their supports (ie- The painted surface made from fabric, paper, wood panel, fabricated board, or other). Painting types include fine art to decorative and functional objects spanning from frescos, oil paint and acrylic on various surfaces, egg tempera on panels, and more. Knowing the materials of any given painting and its support allows for the proper restoration and conservation practices. All components of a painting will react to its environment differently. These material components along with collections care (also known as preventative conservation) will determine the longevity of a painting.[1] The first steps to conservation and restoration is preventative conservation followed by active restoration with the artist's intent in mind.

Conservation and Restoration Methods

Frescos

Frescos are types of mural paintings where the pigment is painted directly into a fresh lime mortar surface. These types of paintings are susceptible to damage from vandalism, time, environmental stressors, and climate changes.[2] Frescos, like most works of cultural heritage,have specific climate parameters for preservation. Humidity and water damage cause mold to develop. The mold aspergillus versicolor can grow on frescos and consume nutrients effectively causing pigment discoloration and wall detachment from rot.[3]

A restorer filling the gaps of the damaged frescos in the crypt of Saint Eustorgio church in Milan, Italy.

Preventative Conservation Methods

Ideally, buildings with frescos would be outfitted with central air with humidity adjusting features to keep the paintings in a cool and dry environment with low humidity. Frescos can be found typically in old churches and other ancient structures such as temples and tombs. These types of structures can be limited with additional means like environmental controls.[4][5]

Damages Found in Frescos

Deterioration of frescos can be caused by environmental pollutants. These pollutants can be physical, chemical, or biological. The many layers can deteriorate from the materials chemical compositions reacting to pollutants or environmental conditions such as humidity, temperature, light, and pH.

Chemical Degradation- Evident with pigment discoloration, stains, and the presence of biofilm.

Physical Degradation- Evident with cracking of layers.[2]

Repair and Restoration

Frescos can be repaired by methods of detaching sections of the fresco. Surface repairs for frescos can be less invasive. Conservators can remedy cracks and minor detachments of frescos with injections of epoxy resin containing micronized silica and lime putty.[6]

Oil Paintings

Oil paint is a medium made up of pigments and an oil binding agent. Oil paintings are painted on various surface support types. Oil on canvas, oil on board, and oil on metal are only some examples of oil paintings on various surfaces. Oil paintings are susceptible to damage from vandalism, time, improper handling, environmental stressors and temperature changes.[4]

Restored Painting- oil on canvas; by Bartolomeo Better; Italian. 17th-Century.

Preventative Conservation

Preventative care for oil paintings is essential for preservation. Excessive light with heat can cause fading to pigments. Proper storage with climate and lighting controls are important especially depending on the support structure. The wooden stretcher behind an oil painting on canvas will expand and contract with moisture causing possible buckling of the canvas and cracking, flaking, or shattering of the paint. Paintings should be stored off the ground in case of flooding. Moisture and water damage can cause mold to develop along with various other issues depending on the materials involved: rot (natural materials), rusting (in metals), warping (of wooden supports), etc.[4]

Acrylic Paintings

Acrylic Paintings were introduced in the 1950's and the material differs from oil paint in chemical and physical properties. This medium is still being

Preventative Conservation

Acrylic paintings require attentive preventative care. Due to the soft nature of the paint attracts and hold dirt and debris creating difficulty when cleaning resulting in darkening colors over time. Due to the characteristic of acrylic paint, varnishes will diminish top layers of the paint and effect the colors vibrancy. Storage of acrylic paintings should be clean and free of dust and heat- below room temperature is best as it will reduce further softening of the top layer of the paint. Exposing acrylic paintings to temperatures ranging near sub zero will case damaging cracking. Acrylic paint is highly susceptible to mold growth. This is a growing concern for artists and conservators as removal cause some degree of damage to the original paint.[7]

Conservation and Restoration Methods

Preventative care seems to be the best methods of conservation as the aging process of acrylic paint is still being studied.[7]

Scientific Tools Used

Conservators need to analyze the inner layers of paintings and their support to identify pigments and unstable layers. They use various tools for types of imaging to disguise materials and damages.

Multispectral Imaging

Multispectral imaging is the capture of a single image viewed in different wavelengths. For imaging purposes of conservation, paintings are recorded in the wavelengths: ultraviolet (UV), visible (VIS) and infrared (IR).[8]

VIS- Visible Light- The photo image visible to the naked eye representing the actual colors of the painting.

RAK-Raking Light- Lighting the painting from the sides to show the small cracks and surface texture clearly.

UVF- Ultraviolet Fluorescence- Lighting the painting with ultraviolet radiation to resulting in fluorescent glowing from the varnishes and previous conservation.

IRR-Infrared Reflectography- when the painting is exposed to infrared radiation and its reflection is recorded. The underpainting or drawing of the painting will become visible with IR radiation.

IRFC- Infrared False Color- When the visible image and infrared image are overlapped to view the areas of different material usage and retouches.

IRF-Infrared Fluorescence- The painting is exposed to both visible light and infrared light causing particular pigments to fluoresce revealing the chemicals and types of paint used.

IRTR- Infrared Transmitted- The painting is flooded with infrared radiation and the verso of the painting transmits radiation. The image taken of the verso will show underdrawings and alterations made by the artist.

Instruments

X-Ray Radiology

X-rays are often taken to detect areas of various heavy metals found in paint such as lead, tin, mercuric sulfide.[8]

X-Ray Fluorescence

X-Ray Fluorescence is a technique used to identify the chemical composition of the materials used to make the paint.[8]

Scanning macro-XRF & Neutron Activation Autoradiography (NAAR)

Scanning techniques that images with element specific characters that are able to reveal underlying paint layers

Materials Sensitive to High Relative Humidity

Material Results Recommended
Paper mold/ stains 40% RH or lower
Painted Wood flaking paint 50-55% RH stable/ constant
Painted Metal corrosion flaking paint 40% RH or lower
Finishes mold/ stains 55-55% RH stable
Textiles mold/ stains 45-55% RH

[9]

Materials Commonly Damaged by Pests

Temperature Damages

Material Results Recommended Conditions
paper becomes brittle

darkening

 65 °F (18 °C)
paint media crosslinking

darkening

 65 °F (18 °C)
pigments, dyes fading 65 °F (18 °C)
lacquered serfaces fading

haze develops

 65 °F (18 °C)
painted surface fading 65 °F (18 °C)
wood fading 65 °F (18 °C)
wood finishes cracks

haze develops

 65 °F (18 °C)

[9]

Material Combination Issues

Combination of Materials Conservation Issues
wood/ paint wood expands and contract, paint flakes
metal/ paint metal corrodes, paint flakes
metal/ plaster alkaline materials corrode metals
wood/ paper paper becomes brittle, stained, dark, acid burned
wood/ wood changes due to expansion and contraction, stress, breaks

[9]

See also

References

  1. ↑ Bockrath, Mark F. (2000). The Winterthur Guide to Caring for Your Collection. The Henry Francis Du Pont Winterthur Museum, Inc. ISBN 0-912724-52-8.
  2. 1 2 Larson, J.H. (2016). "Art conservation and restoration". Encyclopedia Britannica. Encyclopedia Britannic, Inc.
  3. ↑ Bennett, JW (2010). An Overview of the Genus Aspergillus (PDF). Aspergillus: Molecular Biology and Genomics. Caister Academic Press. ISBN 978-1-904455-53-0.
  4. 1 2 3 Buck, and Gilmore (2010). Museum Registration Methods 5th Edition. Washington, D.C.: AMM Press. ISBN 978-1-933253-15-2.
  5. ↑ Appelbaum, Barbara (2010). Conservation Treatment Methodology. Appelbaum. ISBN 1453682112.
  6. ↑ Cacci., ed, Leonardo (2003). La Fenice Reconstructed 1996-2003: A Building Site. Venezia: Marsilio. p. 118.
  7. 1 2 "Museum Conservation Institute Care of Acrylic Paintings". www.si.edu. Retrieved 2016-04-29.
  8. 1 2 3 "Multispectral Imaging - ColourLex". ColourLex. Retrieved 2016-04-25.
  9. 1 2 3 4 Conservation Concerns: A Guide for Collectors and Curators. Washington, D.C.: Cooper-Hewitt, Smithsonian. 1992. ISBN 978-1-56098-174-9.

External links

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