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The conservation and restoration of paintings, typically undertaken by a paintings conservator, employs basic collections care, with recommended conditions to prevent future damage, and restorative treatment methods to art works that already exhibit damage. As paintings widely vary from medium and support, their preventative conservation methods, and conservation and restorative treatments will vary as well. These varying mediums and supports combined makes preventative conservation and restoration complex. Each of these components of a painting can impact the artwork as a whole.

Basic care
Typical, traditional oil, or acrylic paintings are made up of various different types of materials. Each of these materials requires specific care in handling, displaying, storage, and general environmental conditions, that impact the overall condition of a painting.

Backing boards
Using good protective measures such as attaching a rigid backing to a painting on canvas provides several protections. It reduces the effects of rapid changes in relative humidity around the painting, provides some protection from pressure or direct contact against the canvas back, and protects from vibrations caused by handling or moving. Backing boards also serve to protect from dust and dirt, cracks and deformations from handling, and insect activity. Some of the most commonly used types of backing boards include foam core, heritage board, matboard, cardboard/millboard, coroplast, corrugated plastic sheets, acrylic sheeting, mylar, and fabric.

Framing
The frames around paintings are not just for aesthetic appearances. Frames are also used to protect the more sensitive parts of a painting when handled by hand, and reduce the potential for damage if dropped. There are also specialists that work on the conservation and restoration of painting frames.

Handling and moving
The movement of objects places an object at a much greater risk of damage than when it is on display or in storage. Certain techniques and equipment are used any time an art work needs to be transported. These techniques and equipment include using padding lifts and dollies, moving small, fragile objects on carts instead of carrying by hand; lifting objects from underneath by their sturdiest part; and taking extra time and care when on ladders or stairs. In many cases gloves are worn to protect the art work from any dirt or oil that may be on a conservator or object handlers hands. When handling canvas paintings specifically, never presume that the frame is stable and firmly attached. Do not lift or carry a painting by its stretcher bar, or insert your fingers between the stretcher bar and the canvas

Display and storage
It is estimated that a lack of proper routine maintenance and care is responsible for 95 percent of conservation treatments; the remaining 5 percent results from mishandling objects When developing display and storage methods for works of art, issues regarding relative humidity and temperature, light, pollutants, and pests need to be considered.

Causes of Deterioration
Moisture, heat, light, pollutants, and pests can slowly or suddenly cause damage to a painting. These agents of deterioration impact all of the components that make up a painting in various ways.

Relative humidity and temperature
Low or high relative humidity (RH) as well as rapid changes in relative humidity can be be damaging to paintings. According to the Canadian Conservation Institute, there are four types of incorrect relative humidity. These four types include: Damp, over 75% RH, RH above or below a critical value for that object, RH above 0%, and RH fluctuations. "Generally accepted temperature and relative humidity standards for most museum objects and artifacts are 65°-70° F (18°-21° C) at 47%-55$ RH." The best method of controlling the environment is by using a centralized climate control or HVAC system where incoming air is washed, cleaned, heated, or cooled, adjusted to specific conditions, and then injected into the storage space. An appropriate alternative is a localized climate control system where air conditions cool the air and absorb some of its moisture while filtering out gross particles. They do not condition the air, nor do they filter air pollutants.

Light
Both visible and ultraviolet light are responsible for causing damage to paintings. In particular, organic materials such as paper, fabric, wood, leather, and colored surfaces. "Fugitive dyes and colorants used in paints will eventually discolor under exposure to ultraviolet light. The fading of pigments and dyes in paintings will affect the color balance of the image." Damage from natural and artificial light exposure can be mitigated by displaying paintings out of direct sunlight, use of blinds, shades, curtains, or shudders, filters on nearby windows, installing dimmers and appropriate wattage light bulbs, and displaying paintings a safe distance from a light source to limit heat exposure

Pollutants
Pollutants can be described as gasses, aerosols, liquids, or solids that have a chemical reaction with any part of a painting. There are three types of pollutants. Airborne pollutants, pollutants transferred by contact, and intrinsic pollutants.

Airborne pollutants which originate from atmospheric sources (ozone, hydrogen sulfide, sulfur dioxide, soot, salts), or emissive products, objects, and people (sulfur-based gases, organic acids, lint, and dander). Their effects can include acidification of papers, corrosion of metals, discoloration of colorants, and efflorescence of calcium-based objects.

Pollutants transferred by contact include plasticizer from PVC, sulfur compounds from natural rubber, staining materials from wood, viscous compounds from old polyurethane foams, fatty acids from people or from greasy objects, and impregnation of residue of cleaning agents. The effects of these pollutants can include discoloration or corrosion of a paintings surface.

Intrinsic pollutants are composite objects that have compounds that are harmful to other parts of an object. The effects of these pollutants includes deterioration of the object, acidification, discoloration or staining on an object, speed up degradation processes caused by oxygen, water vapor, or other pollutants.

Pests
Pests such as rodents and insects have the potential to cause considerable damage to works of art. Preventative measures that may be taken to protect paintings from pests include upgrading building structures to obstruct pest entry, installing better cabinetry with good seals, better control of temperature and humidity in collections and storage areas, keeping food and other organic materials from collection areas, and treatment of outbreaks.

Acrylic paint
There are two types of Acrylic paints used in acrylic paintings. There is solvent-based and water-based. Solvent-based acrylic paints are soluble in mineral spirits, and water-based acrylic paints are water-soluble. Acrylic paint differs from oil paint in both its quick drying time, and how the paint dries. Acrylic paint dries in as little as thirty minutes, and dries by the evaporation of solvent of water.

Blacklight or fluorescent/luminous paint
Black Light or Luminous Paint is typically made up of fluorescent dyes mixed into paint. These dyes are not a typical dye, but rather a pigment that is suspended in a carrier or resin. This pigment is what gives off a glow when exposed to ultraviolet light. This glow or light is created by the energy that is released from the pigment. While the fluorescent paint layers reflect light, they lose their color intensity over time

Egg rempera
Egg Tempera is made up of egg yolk water, and pigment. These ingredients are mixed together to create a thick paste that dries quickly, but can take six to twelve months before it completely cures. Egg Tempera's fast drying property makes it difficult to correct or revise. Egg Tempera and can develop cracks over time that are visible to the naked eye, and flaking caused by air bubbles. Tempera paintings are thought to be more resistant to materials typically used during cleanings. However, they are susceptible to abrasions from routine dusting, washings, and removal of old varnish layers.

Enamel paint
Enamel or nitro-cellulose based paints were originally designed for commercial use, but have also been used in artist's paintings such as Jackson Pollock and Pablo Picasso. Enamel paints are oil, latex, alkyd, and water based. This paint dries rapidly and has a glossy finish once dry.

Encaustic
Encaustic is a method of painting that involves dry pigments mixed with hot beeswax, then applied to the surface of a support such as wood or canvas. A completed painting is then finished by taking a source of heat to reheat the surface and fuse it together. Encaustic paintings do not require a varnish, are resistent to moisture, and do not yellow.

Fresco
Fresco paintings are a painting technique used on walls where pigments are mixed in water and then applied to wet lime plaster. As the wall dries, the plaster hardens, a transparent layer is formed, and the pigment becomes a part of the wall. Fresco colors needed to withstand the alkaline action of the line. Typical colors ranged from vine and ivory black to yellow ochre, umber, and cinnabar. Fresco paintings don't require a protective finish or varnish, but are especially susceptible to damage from damp conditions. Such damage could include paint layers flaking or detaching from the wall, or a biological attack such as mold.

Scroll and screen paintings
Scroll Paintings,Hanging and Hand, and screen paintings are made of ink, color, pigment, silk and paper. Scroll paintings often are multiple layers of paper and silk attached to wooden bars called a stave and dowel. Screens are often single panels that are joined together by paper hinges that fold into each other like an accordion. Scrolls and Screens are vulnerable to damage from fluctuations in temperature and humidity. Exposure to light for extended periods of time can cause silk and pigments to fade, and paper to darken. Glazes and films that filter ultraviolet light can help to prevent damage from UV radiation. Creases and abrasions may also form on scroll paintings from repeated rolling and unrolling, squeezing the scroll or tying the cord too tight. Screens can become distorted from uneven tension between the back and front side panels

Lacquer
There are a variety of lacquers that have been, and continue to be used such as Urushi (unprocessed lacquer), Guangqi (processed), Nitrocellulose, lacquers with acrylic resins, and water-based lacquers, but the most well known lacqueris Urushi lacquer. This lacquer paint is made from raw lacquer or sap taken from trees. It is then heated, filtered, and applied in thin layers to supports such as wood or metal. The lacquer is left to cure before it is polished, and another layer is added. The number of layers may vary, and each can be left in its natural transparent state, or colored with pigments to create Lacquer painting. While lacquer is a hard material, it is susceptible to cracks and loose joins from fluctuating temperatures and relative humidity. Extended exposure to light can also cause lacquer to lose its durability.

Latex Paint
Latex Paint (Also See Acrylic Paint)

Oil paint
Oil based paint consists of pigments mixed into drying oil with various other ingredients that can be mixed in, and conditioned in several ways to modify its various properties and drying. Oil paint can be durable, but is still vulnerable to cleavage, excessive cracking, lifting, and flaking. Oil paint is more susceptible to damage in low relative humid conditions, and fluctuations can create stresses in the paint layers.

Pastels
There are two types of Pastels. Pastels that are made of pigment particles bound together with a binding agent, and oil pastels that have pigments mixed with wax and non-drying oil. Pastels that are pigment particles bound together take on a more chalky and loose powdery characterization, and are secured to its supports using fixative or diluted resin in solution. Oil pastels never fully dry, and are sensitive to scrapes, dust and dirt. Using a glaze over the surface can help to protect the oil pastel.

Watercolor and gouache
Water color and Gouache paintings are pigments mixed into water-soluble gums that are applied onto paper or rigid board supports. Due to its thin washes and light colors, watercolor paintings are very light sensitive. Also, due to their exposed support they are vulnerable to damage from dirt, dust, and pollutants. Gouache paintings can form layers like acrylic and oil paint, but is still vulnerable to the same agents of deterioration as watercolors.

Painting supports and painted surfaces
Because the material that makes up the support can have a major impact on the overall deterioration of an artwork, it can determine the best method for handling, storing, and displaying an object.

Architectural structures (i.e. walls & ceilings)
Architectural Structures (i. walls, ceilings)

Canvas
Canvas Linen, hemp, jute, burlap, and cotton.

Ceramics
Ceramics vary widely in their construction, style, and use. There are three types of ceramic objects. They are earthenware, stoneware, and porcelain. Each of these types of ceramic objects are fired at different degrees and come in different colors. The materials used in their construction are often a clay body, and some times mixed with sand, shell, chalk, mica, and ground-up fired ceramics. The surface of these ceramic objects are finished with glaze and fired in a number of ways. Decorations with gold, paint or enamel are applied over the glaze. These overglaze decorations are susceptible to abrasions or chemical damage from cleaning and handling. A ceramic object is also vulnerable to weeping and crizzling from fluctuations in relative humidity and temperature.

Cloth or textiles
Cloth or textiles are typically made from natural fibers such as wool, silk, cotton, linen, and hemp. However, some textiles more recently have been created with modified natural fibers such as Rayon. Textiles can make up many different objects from cushions to dresses. All with varying degrees and types of degradation. Light typically causes dyes to fade, and some fibers (silk) are more sensitive to physical damage from light. Low light levels are recommended to prevent damage. Mold and mildew caused by high levels of humidity and improper storage can cause irreversible damage. Damage can be mitigated with proper relative humidity levels and storing of textiles in acid-free tissue or clean cotton sheets. Textiles are especially vulnerable to attacks from pests such as moths and silverfish.

Glass
Paintings on Glass are particularly challenging because of first the fragile nature of glass, and second the smooth surface of glass that makes it difficult for paint to adhere to the surface.

Ivory
Paintings on Ivory are typically small, and the most commonly used paints were (watercolor, tempera, and gouache) directly on the surface of the ivory. The ivory was usually thin, translucent in appearance, and typically attached to a secondary support made of paper or card. Miniatures of these designs were frequently sealed in metal lockets or cases. The paint on the surface of ivory is very delicate and can be easily rubbed off, small amounts of water (breath, condensation or residues from cleaning) can affect the image. Ivory is also very sensitive to environmental changes. Ivory supports can be prone susceptible to warping and splitting from fluctuations in relative humidity.

Metal
Metal Various types of metal plates have been used as supports for paintings. These include: "silver, tin leaf, iron with tin on either side, copper, or copper coated with silver, tin, lead, or zinc. Enamel paint has been used on copper, but typically oil paint was used on metal supports. Metal does not respond to changes in relative humidity by expanding and contracting. However, metal can corrode over time staining paint or creating eruptions and flake in the paint. It is also susceptible to physical deterioration such as dents, tears, and scratches.

Outdoor murals
Outdoor Murals

Paper
Works of art on Paper range from watercolor paintings, prints, posters, and drawings using a variety of media from watercolor, charcoal, pastels, and colored inks. Due to the fibers in its construction, paper is vulnerable to various types of damage. Paper is easily torn, creased, or stained during handling. When exposed to light colors fade and the paper itself can discolor too. Works of art like watercolors and Japanese prints are especially vulnerable to fading. High relative humidity can cause paper to swell making it appear wavy or winkled. When exposed to long periods of high humidity, mold can form.

Wood
(Furniture, Panel, Lacquer Painting, Stretcher Bar, Wood Block Prints)

Wooden supports depending on what kind of object they are used for are made from hard and soft woods. Some types of woods that artists use are poplar, beech, spruce, pine, chestnut, cherry, mahogany, and cypress. Wooden supports are susceptible to several kinds of deterioration. These include insect infestation, fluctuations in humidity/temperature causing warping and cracking, and structural damages. Cradling was previously used to correct warping by thinning the original structural support and then adhering the cradle to the reverse side of the support. However, it has become widely understood that cradling can be harmful to the paint and ground layers. Conservators today instead work to preserve what remains of the wood support rather than making corrections.

Infrared reflectology
Conservators use infrared lights to see what lies directly underneath the surface of paint layers. This tool can help conservators identify previous restoration treatments, where damage was restored, changes in the paintings composition, and any underdrawing.
 * Multispectral Imaging
 * X-radiography
 * Radiography penetrates entirely through the painting. Including the canvas, and wood panels or stretcher. Conservators can use x-radiography to find changes in composition, previous restoration treatments, and how the paintings support was constructed.
 * X-ray fluorescence
 * Scanning Macro-XRF & Neutron Activation Autoradiography (NAAR)

Ultraviolet/visible fluorescence
UV lamps are used by conservators to be able to identify pigments, varnishes, and retouchings from previous restoration treatments. It is limited to the upper layers of the painting.

Conservation treatments and processes
After determining an artworks condition, stability, history of previous restoration, and documenting and photographing the examination, future conservation treatments can be determined. The results of conservation treatments often yield a more "stable paint layer and support, more appropriate aesthetic presentation through cleaning, and a more unified paintings through the reintegration of the paint losses. It is not possible to restore a painting to its original form, but with careful preservation, documentation and restoration, conservators can help to extend the life expectancy of a painting." These treatments depend on the materials that make up an artwork. They can include:

Consolidation
Securing areas of loose paint with adhesive.

Cleaning
Removing or reducing "dirt, grime, discolored varnish, and retouching with solvent mixtures or mechanical means."

Facing
Securing the paint layer with tissue and adhesive before corrective structural procedures.

Transferring
Involves removing the original canvas or wood support, leaving the paint and/or ground layer, and re adhering the layers to a new support.

Cradling
Cradling involves applying a wood latticework on the backside of a panel painting to prevent warping. Before cradling, the wood support is typically thinned.

Lining
The lining of paintings is adhering a new canvas to the reverse side of the original canvases for added support.

Lining Removal
Removing the old lining of a canvas because the adhesive has failed and resulted in delamination between the original canvas and the lining canvas.

Varnishing
Applying "saturating varnish of either a synthetic resin or a stabilized natural resin varnish."

Filling
Adding "putty-like material to areas of paint loss."

Inpainting
Inpainting is applying synthetic or natural resin medium restoration paints to areas of paint loss to restore the "visual unity" of the painting.