Source: http://www.conservation-wiki.com/wiki/Inpainting_(PCC)
Timestamp: 2019-04-26 14:13:17+00:00

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Inpainting is the addition of appropriate media to fills, repairs, and areas of loss in a work of art or artifact to restore visual integrity by compensating losses of media, or in some cases support, without compromising original intent or materials. The intent is to suggest the continuity of image and/or background, to create the illusion of wholeness, and to minimize the distraction of losses. This chapter will deal primarily with the compensation of image loss with references made to the preparation of fills or inserts, alternatives to inpainting, disguising of stains, etc. (See Filling of Losses).
The Photographic Materials Group has a related chapter on Inpainting of Photographic Prints .
Some conservators consider inpainting not to be a genuine and necessary component of conservation and that it is even a questionable aspect of restoration since the line between reconstruction and forgery or deception can be very ambiguous.
Issue of reversibility: The new draft of the AIC Code of Ethics states under Compensation for Loss (#23) that “... such compensation should be reversible.” On original artifacts, every effort should be made to inpaint in a reversible manner, recognizing that this is not always possible given the relatively simple structure of works of art on paper. Few, if any inpainting materials are completely reversible, especially since many inpainting media become increasingly insoluble with time. Inpainting on an original surface, therefore may become a permanent part of its structure. (IB) For example, pastel pigments can become permanently embedded in paper fibers; watercolors can be absorbed easily by soft-sized papers; coated papers may not withstand the manipulation necessary to remove dry or wet inpainting materials without harming the surface; etc. Exercising restraint is essential due to the inherently intractable and relatively non-reversible nature of compensation on paper. (JB) Application of an isolating layer may improve reversibility, as may using as thin and non-penetrating a layer of media as possible.
There is general agreement amongst conservators that inpainting and reconstructions are restricted to damaged or inserted areas, and should not be used to intentionally alter the original or existing character of a work of art. Inpainting to strengthen a weak impression or signature is not considered to be appropriate.
Disguising damage may interfere with interpreting an artifact whether for historical or artistic information, or for condition assessment during resale of an artifact.
Every effort should be made to render inpainting detectable by common examination methods (examination with microscopes, ultraviolet light, raking and specular light, radiography, etc.). Inpainting with the same media as found in the object may interfere with detectability of inpainting, but is considered by some conservators to be unavoidable, especially in cases where it produces the best results. Use of different pigments than those found in the object may increase detectability.
Documentation, written and photographic, is especially important since inpainting on paper objects is not always removable or easily detectable. Documentation should include exact location of inpainting and the media and technique of application. Photographs taken before compensation and inpainting are particularly critical.
Consultation with the artist may be desirable in some cases, in particular regarding materials, techniques, and artistic impressions. There may be cases in which the artist is asked to repair his/her own work. Some regard inpainting by an artist less problematic, ethically, than inpainting by a conservator. It is important that the artist understand the ethical principles underlying compensation. Also, it is incumbent on the conservator to inform the custodian or owner that the nature and value of the artwork can be altered by an artist's proclivity to enhance his/her former work rather than to simply restore it. (RGC) It may be helpful to explain to the custodian/owner and artist that the skills required for inpainting differ than the painting skills used to create a work of art.
Degree of distraction of losses, etc. which may compromise appreciation of artifact: Location (margin versus image), severity, and number of areas to be inpainted, should be considered as well as scale of damage or loss relative to the whole object. Also, size of the object and viewing distance affect choices.
What may first appear as “losses” may actually be a result of an artist's working method or historically significant corrections or alterations. In addition, losses caused by use or wear may be an important determinant of the value of an artifact. (HM) Compensation of these “losses” would not be appropriate.
In some cases attempts to inpaint may be more distracting than the loss or stain itself. Inpainting dark-colored damages with a lighter, opaque medium will in most cases result in a noticeable mark. (IB, ECL) However, it is a judgement call depending upon the object because sometimes the result is less noticeable than the original mark.
Degree of compensation will vary according to object, collection, and custodian. After the decision to inpaint has been made, consider degree of compensation: general toning versus exact color match, reconstruction of missing design versus simply matching background color, and sympathetic, but detectable, versus more extensive compensation. Type and extent of inpainting should be discussed and agreed upon by owner or custodian and conservator.
Viewing conditions (taking into account the size of object and viewing distance), matting and framing, and lighting should be considered during inpainting.
Reconstruction of missing design may be considered more appropriate and common if working on an insert rather than on the original.
Close examination and identification of physical characteristics of the media and support are important in order to match or approximate them during inpainting.
Support: Absorbency, color, texture, presence of coating, general condition, etc. See Support Problems. For example, determining the degree of absorbency of the support will dictate the amount and strength of an isolating layer required to increase reversibility of inpainting. In many cases, approximating the surface texture of the support may be as important as getting an exact color match during compensation.
Media: General composition (binders, pigments, etc.), color, surface gloss, friability, texture, thickness of application, etc. See Media Problems. Note subtle characteristics of media when selecting and manipulating inpainting materials.
Damage: Nature of damage (abrasion of top paper fibers, superficial loss of support, loss of design, scratch in media or coating), location of losses (margin vs. image), extent and number of losses, etc.
Characteristics of Inpainting Materials: Physical form (stick, pencil, powder, liquid), presence of binder and additives, viscosity, solubility (carrier solvent), translucency/opacity, friability, surface gloss, general covering power of pigment or media, ease of control during application, etc.
See listing of specific media in Compressed Stick and Pencil Colors and Wet Media.
Durability: Natural aging characteristics (i.e., yellowing, cracking), sensitivity to abrasion, etc. may affect choice of inpainting materials.
Reversibility (Solubility): Media which may have a water or organic solvent carrier during application may not be soluble in the same solvent upon drying. (For instance, acrylic dispersion paints are water-borne, but are not water-soluble when the film has dried.) Also, many media become increasingly insoluble or intractable with time.
Light Stability: See Stability (Lightfastness) Rating of Some Commonly Used Pigments. Light stability of pigments and dyes vary. In general, inorganic pigments are less susceptible to fading than organic pigments and dyes.
Some pigments contain transition metals which sensitize cellulose to oxidative reactions catalyzed by light and moisture. Sensitizing compounds/pigments include titanium dioxide, zinc sulfide, zinc oxide (found in zinc or Chinese white), and copper greens. (Media Problems, “These oxidizing species can accelerate the fading of several dyes and pigments when mixed together with zinc oxide.” (Daniels, 1990, 236)). A halo of discoloration in the paper may be observed surrounding the pigment.
Oil paints are rarely used for inpainting on unprepared paper due to staining of the cellulose by the oil binder.
Media in the artifact may be sensitive to accidental contact with the liquid carrier of some inpainting materials. For example, red chalk, pastels, and certain kinds of crayons permanently darken upon wetting with water or organic solvents.
Friable inpainting materials can be transferred and smudged unintentionally, and subsequently can be difficult to remove.
The more simple the mixture, the less chance for pronounced metamerism of the resultant color.
Lighting: View the object and inpainting in a variety of light sources and angles (i.e., raking, specular and normal illuminations), to evaluate color, surface gloss, and texture.
Orientation of Object: An object can be inpainted in a horizontal or vertical position. If working on a table, the object should occasionally be viewed vertically as this is the orientation in which it will typically be displayed. View the object from all sides and angles, vary the viewing distance, and periodically use magnification.
Matting: Inpainting while the artwork is placed on a mat of appropriate color may be helpful in achieving a good color match due to translucency of the paper support and influence of the surrounding mat color. Sometimes mat color can be adjusted or locally toned to avoid inpainting the object.
Materials listed below can be purchased at art supply stores or through art and conservation supply catalogs. Note that any of the brand-name materials listed below, especially those of complex composition, may be altered by the manufacturer at any time. (IB) Lists of manufacturers and brands are only partial and do not represent an endorsement. Also see Media Problems.
The following materials can be used to size insert papers or can act as local isolating layers for inpainting. See Adhesives.
Cellulose Ethers (primarily methyl cellulose, but also sodium carboxymethyl cellulose, hydroxypropyl cellulose, and ethyl hydroxy ethylcellulose).
Consider viscosity grade and concentration appropriate for type of paper, i.e. shorter chain polymers penetrate while longer chain methyl celluloses form films on paper surface. (LHP) For a discussion of stability see Feller and Wilt, 1990.
Pigments are described as organic (vegetable, animal or synthetic in origin) or inorganic (mineral, earth or synthetic in origin) particles which do not dissolve, but remain dispersed in a liquid. (Dyes are in solution.) Lakes are pigments made by precipitating an organic color or dye onto an inorganic base. Particle size is dependent upon grinding and pigment type. Powdered pigments can be applied dry or mixed with binders.
Dry artists' pigments are manufactured and/or distributed by Winsor & Newton, Kremer Pigments, Daniel Smith, Conservation Materials, Ltd., Schmincke, Old Holland, Sennelier, etc. Pigments are available from manufacturers and through art supply stores.
White (and/or Inert) Pigments (JB): The classic Chinese (zinc oxide) white and titanium (dioxide) white, typically found in watercolor inpainting palettes, are in many instances too brilliant and opaque for paper inpainting, where the media and support are often warm, semi-transparent and inherently less brilliant. Other white pigments may be mixed with cellulose gums (methyl cellulose and carboxymethyl cellulose), other gums or resins to produce more effective watercolor inpaints.
Calcium carbonate whites such as chalk (whiting), marble white (ground marble) or oyster shell white (ground from mollusk shells) will provide softer, warmer, more transparent whites that will be closer in value to paper and media tones. Gypsum (calcium sulphate) may also be useful, particularly if a gesso underlayer needs to be reconstructed; however, it is not an ideal white pigment due to its low refractive index, its absorptive nature, and its affinity for water.
White china clay (kaolin, white bole) has a wonderfully warm and soft optical quality, that reads more naturally than zinc or titanium whites. Inpaints containing kaolin (frequently added as a filler in clay-coated and other papers) may be burnished after application and drying to align the clay platelets and provide increased surface uniformity and sheen. When adding kaolin to inpaints, moderation is advised and additional medium is recommended; paints comprised primarily of kaolin pigment with insufficient binder have poor adhesion and may crumble and/or spawl.
Extenders, Fillers, and Matting/Flatting Agents (JB): The conservator is encouraged to study and explore the use of inert fillers and matting or flatting agents used extensively by the paint formulation industry. Examples of particles that may have applications for paper inpainting are silicas (natural and fumed), glass balloons, talc, kaolin, alumina, and so on. For an introduction to the properties and applications of these paint modifiers, refer to bibliography entry under Federation of Societies for Coatings and Technology.
“Natural” Pigments, Pigments with Low Tinting Strength, and Gritty Pigments (JB): The eye adjusts easily to pigments of natural derivation (i.e., natural iron earths) or pigments of low tinting strength, which can be added in tiny amounts to produce very subtle color shifts in inpainting, enabling great control. For some toning or inpainting situations, a pigment may be selected not as much for its color as for its individual appearance or configuration. For instance, charcoal black has large, splintery particles that stand out visually and produce a wonderfully gritty effect, very different from the uniform black produced by ivory black. Viridian, silicas (available in a wide range of mesh sizes, natural and synthesized), green earth, certain iron oxide earths, and Van Dyke brown (the latter not especially stable or permanent) have visibly gritty particles and may be effective for certain inpainting effects. To gain the benefit of the pigment grit, one must begin with pure pigments, rather than paints where the pigment grit has been negated by extensive grinding.
Interference, iridescent, pearlescent or lustrous pigments: Nacreous pigments comprised of tiny mica platelets coated with thin films of titanium dioxide, and/or iron oxide or other pigment, to form a wide range of luster, “metallic” (emulating shades of metals such as gold, silver, bronze, copper, etc.) or color effects. These pigments are essential for matching iridescent or pearlescent colors appearing in modern prints and acrylic dispersion paints on paper. With good stability and lightfastness, pearlescent pigments are excellent substitutes for pigments made from metal flakes, which oxidize and tarnish. The pure pigment may be mixed with the medium of choice or mixed into other paints as needed. Refer to literature and samples from: Mearl Corporation (Mearlin Luster Pigments), 217 N. Highland Ave., Ossing, NY 10562, 915-736-3300, 800-253-8605 (fax); and EM Industries (Afflair Pearl Lustre Pigments), Plastics & Coatings Group, 5 Skyline Drive, Hawthorne, NY 10532, 914-592-4660.
Fluorescent pigments: Known under the trade name “Day-Glo”, these brilliant modern pigments are found in silkscreen or other prints from the 1960's to the present. Available in approximately ten colors, these pigments contain dyes that absorb invisible and near visible ultraviolet light, giving off a glowing emission of a longer wavelength than that absorbed. With exposure to light and aging, these pigments lose their fluorescent strength and the dye component may fade as well; nonetheless, Day-Glo's are indispensable for replicating the effect of Day-Glo paints used on artifacts by Pop and other artists. For literature and samples contact: Day-Glo Color Corp., 4515 St. Clair Ave., Cleveland, OH 44103, 800-289-3294.
Metallic pigments: Bronze, aluminum, and other flake metal powder pigments are reactive and not recommended for most paper compensation applications as they readily tarnish, turn dark brown-green, and can interact with paper and/or metal.
Gold powder and/or gold leaf: Powdered true gold (either commercially prepared, or prepared in the conservation studio by grinding scraps of gold leaf) is inert and may be mixed with a binder of choice (e.g., gelatin in water or Acryloid B-72 in solvent). Gold powder, and/or continuous gold leaf, are indispensable for accurately matching true gold found on artifacts. To produce gold powders in a wide range of colors, select desired shade of gold leaf; add leaf to a honey-water slurry and grind with a mortar and pestle; rinse with water, pour into a tall jar and allow gold to settle; decant rinse water, rinse and allow to settle again; decant water and allow gold powder residue to dry. Note, however, that the use of true gold to compensate gold losses may make it difficult to distinguish restorations from original.
Charcoal: Made by carbonizing wood sticks and composed of grey-black splintery particles. Available as vine or compressed charcoal sticks, or in pencil form. No binder is present in charcoal sticks. (Jirat-Wasiutynski, 1990, 122–4) Some pencils, such as Conté brand charcoal pencils, may contain additives such as waxes, clay, and finely ground pigments.
Graphite: Manufacturing process of synthetic graphite leads is basically the same as when first developed in 1794 - graphite powder is mixed with fine clays, dried, and then fired. Historically, antimony, spermaceti and other waxes, shellac, rosins, gums, and at times lamp black were added. (Watrous, 1957, 142) Graphite is available in stick, pencil, and powder forms. Hardness of stick or pencil varies with proportion of graphite to clay; “waxes or fatty oils are frequently used to impregnate rods to improve smoothness of marks”. (Newman, 1980, 33–34) Degree of hardness ratings: H hard, HB medium, and B soft; numbers, in ascending order, designate higher degree of hardness or softness within appropriate category.
Working characteristics: Graphite can be blended depending upon degree of hardness. Appears shiny and slightly iridescent. Tone and metallic sheen are controlled by graphite hardness and application technique. Softer forms of graphite can be smudged or transferred if heavily applied.
Chalks: Natural and fabricated black, white, red, and brown chalks.
Natural chalks: Black chalk's principal ingredients are carbon and clay. White chalk is composed of calcite (calcium carbonate); however, another chalk not often found is soapstone, a variety of talc (hydrous silicate of magnesium). (Watrous, 1957, 106, 108) Red chalk contains iron oxide from the mineral hematite and clay; presence of clay increases softness. Today natural chalks are rarely available in stores.
Fabricated chalks: Traditionally contained a binder of gum tragacanth; cellulose ethers often are used today. See Pastel Sticks under Compressed Stick and Pencil Colors).
Working characteristics: Chalks are blendable and may smudge or transfer if heavily applied. Can be difficult to control in stick form when inpainting small areas. Chalks can be applied dry or wet with brush, etc. or mixed with binders.
Conté Crayons: Made of compressed pigments and binder; are grease-free and harder than pastels. Colored pigments or dyes appear to be added to obtain various shades of greys. Sanguine crayons have a kaolin base containing red iron oxide (Daniel Smith Inc. catalog).
Working characteristics: Conté crayons feel slightly brittle yet waxy compared to charcoal, chalk or pastel. They are somewhat blendable, but are more resistant to gentle smudging than pastels. Although, generally matte in appearance, they are more shiny than pastels.
Pastel Sticks: Composed of pigments, aqueous binder, and fillers. Binder was traditionally a vegetable gum (often gum tragacanth) or proteinaceous glue; today methyl cellulose or similar cellulose gums are used. Clay, plaster of Paris, kaolin, alabaster, zinc and titanium whites, silica, and aluminum are added as fillers to obtain tints and give body to the sticks. Fungicides may be added because pastels are susceptible to mold growth; however, synthetic binders, such as methyl cellulose, are less vulnerable. (Ellis, 1987, 85) Light stability is dependent upon pigments or dyes found in particular pastel sticks - most light-stable colors tend to be inorganic pigments; least stable tend to be organic pigments. Pastel sticks are sold in three grades - soft (most common), medium, and hard.
Common brands/manufacturers: Rowney soft pastels (England), Schmincke soft pastels (Germany), Rembrandt soft pastels by Talens (Holland), Sennelier soft pastels (France), Grumbacher soft pastels, Lefranc & Bourgeois pastels (France), Girault soft pastels, and Conté Color Crayons.
Pastel Pencils: Composed of pigments mixed with binder, fillers, and other components. See Pastel Sticks under Compressed Stick and Pencil Colors).
Working characteristics: Pastel pencils are blendable, appear matte, and are more controllable than pastel sticks. Water and organic solvent sensitivity depends upon brand and color composition of each pencil.
Conté Pastel Pencils: Leads of pastel pencils harder than pastel sticks (product literature). Seem to be more friable than Carb-Othello.
Working characteristics: Colored pencils are blendable, but not overly friable; however, they can transfer if applied heavily. May appear more glossy on application than pastel pencils, especially on soft papers. This can be avoided by repeated light application of pencil versus a single heavy application. (PV) Water and solvent sensitivity depend upon brand and color composition of pencil and amount of liquid present. Will transfer if heavily applied and not coated or fixed. Can be used directly or mixed with binders. Can be applied dry and then brushed over with mineral spirits, etc. to achieve a wash effect. Harder pencils can scratch the surface of some papers to which they are applied.
Reversibility: Colored pencils can be reduced partially by eraser. They tend to be more difficult to remove after having been applied wet. Use of isolating layer increases reversibility by eraser or damp swab.
Stability: There is great concern for light stability of colored pencils: “In general, earth colors (including grays) exhibit excellent to very good lightfastness. Blues, greens and often yellows, however, are very inconsistent varying significantly in stability from one manufacturer to another. Finally, the violets, reds, oranges, and pale tints are often problematic and most susceptible to significant fading upon exposure to light.” (Norris, 1993 draft, 12–13) Lightfastness of lake pigments (e.g., purple magenta and dark violet) is poor. Manufacturers often vary pigments and dyes, so the conservator should test each individual pencil for lightfastness. ASTM and pencil manufacturers are working on quality standards and labelling to be adopted in the near future. After testing, the National Artists Equity Association concluded that half of the pencils in any manufacturer's line fade significantly and no one brand is clearly superior to the others.
Berol Prismacolor pencils: Composed of methyl cellulose binder, kaolin and bentonite clays (for additional strength), 20–30% wax, and are heavily pigmented with both inorganic and organic pigments. High pigment concentration results in good covering power. (Norris, 1993 draft, 12) Berol also manufactures Verithin colored pencils which are harder, less creamy, and slightly more erasable than Prismacolor pencils.
Colored Water-soluble Pencils and Crayons: Some colored pencils and crayons are made with water-soluble binders and dyes. These tend to be more commonly used for toning inserts than for inpainting directly on artifacts. If used for inpainting, water sensitivity of pencil or crayon could preclude subsequent water treatments due to possible bleeding.
Working characteristics: Water-soluble pencils and crayons are similar to other colored pencils. In addition, they may be applied dry and then gone over with a wet brush, or dipped into water and applied damp.
Reversibility: If applied dry, these pencils and crayons can be reduced partially with eraser, but are more irreversible if applied wet.
Derwent Water-soluble Sketching Pencils: Similar in appearance to graphite with unaided eye; however, under the microscope, seem to contain both graphite and black pigment or dye.
Caran d'Ache Neocolor II water-soluble crayons and soft pencils: Made in Switzerland.
Working characteristics: These sketching pencils are somewhat blendable and water-soluble. See Colored Water-Soluble Pencils and Crayons under Compressed Stick and Pencil Colors).
Crayons: Crayons are described as drawing materials containing oily, waxy or greasy components or combinations of water-soluble and fatty binders. They are used infrequently for inpainting directly on objects due to limited reversibility.
Lithographic crayons: May contain lamp black, wax, tallow, spermaceti, soap, and shellac. (Watrous, 1957, 120; and Mayer) Available in range of softness.
Oil pastels and sticks: May contain oils (linseed or vegetable), waxes, and pigments.
Special note: Modern watercolor and gouache may differ from traditional paints. Check the product label carefully. For instance, some products with “gouache” in the title actually contain an acrylic component.
Reversibility: Watercolor and gouache may be reduced with damp swabs depending upon age and penetration of the inpainting layer into the paper, as well as the paint composition. Reversibility increases with application of an isolating layer or addition of a resoluble binder, e.g., methyl cellulose.
Stability: In watercolors, the pigments are not protected by excess binder as in oil or acrylic paints and therefore, are more vulnerable to light and pollutants. Also, they tend to be applied in thin films exposing pigments to increased exposure and subsequent damage. References on the stability of pigments and watercolor paints are ASTM D5067 Standard Specification for Artists' Watercolor Paints and The Wilcox Guide to the Best Watercolor Paints by Michael Wilcox. Manufacturers may change components so conservators may need to test individual paints for lightfastness.
Manufacturers include: Winsor & Newton, Grumbacher, Schmincke, Rowney, Lefranc & Bourgeouis, etc.
Photographic retouching paints (e.g., Marabu Retouch Set, Schmincke Positive Retouching Colors): These are essentially watercolor or gouache paints composed of pigments bound with gum arabic, dextrin or “sugary substance”. Colors are available in matte and glossy and appear somewhat opaque when applied. (Norris, 1993 Draft, 11/12) Some conservators suspect that dyes may be mixed with pigments for certain colors.
Drawing Inks: Composed of finely ground pigments or dyes dispersed in aqueous binder with a wetting agent and preservative. India and sumi inks are carbon-based; some fountain and felt-tip pen inks are dye-based. Binders of water-resistant inks contain shellac or rosin combined with borax. (Watrous, 1957, 69) Black waterproof inks usually are composed of carbon black pigment in a colloidal solution of shellac soap (or synthetic resin); chromatic waterproof inks contain pigments, chiefly organic, in the same formulation, or aqueous anionic or cationic dyes in shellac solution. (Bredereck, 1988, 115) Inks tend to be glossier than watercolors.
Higgins India Ink: Waterproof black ink by A.W. Faber-Castell.
Acrylic Resin Paints: Contain pigments in acrylic resin(s). Used frequently by paintings and objects conservators. Dilution with solvents required for translucent effects. Tend to remain soluble in organic solvents. Can be modified with acrylic resins.
Acrylic Dispersion Paints: Composed of pigments in acrylic polymer or copolymer dispersion of acrylic acid, methacrylic acid or acrylonitrile. (Sometimes termed latex, acrylic latex or polymer emulsion paint.) (Norris, 1993, 16) Acrylic dispersion paints may contain additives including plasticizers, anti-foaming agents, thickeners, fungicides, wetting agents, etc. Labels often list pigment(s) present and lightfastness rating. Acrylic dispersions are most often used to tone inserts and lining papers.
Brands include: Liquitex Acrylic Artist Color, Winsor & Newton Artists' Acrylic Colour, Golden Artist Colors, etc. Liquitex and Golden paints are formulated with Rhoplex acrylic dispersion binder modified with general additives.
Winsor & Newton Liquid Acrylic Color: Pigments in an alkali soluble acrylic solution (Winsor & Newton product literature). These are transparent colors with a consistency similar to ink. Are diluted with water, but are water resistant upon drying. Reversibility and light stability unknown.
Dyes: For description of dyes used in retouching photographs see the Photographic Materials Group chapter on Inpainting of Photographic Prints.
Dry Cellulose Powder: Whatman cellulose powder available from Fisher Scientific. Microcrystalline cellulose (FLUKA) has a smaller particle size than alpha cellulose powder. (LHP) Cellulose powder has been used for filling small superficial losses in paper support or along tears, and for covering dirty tear edges, abraded areas, etc. Powder, originally white, can be “toned” by heating on a hot plate, periodically stirring the powder to get even darkening of color. Range of colors from beige to brown can be obtains by adjusting heat and time (See Use of Paper Fibers or Cellulose Powder under Alternatives to Inpainting for notes on application).
Additional materials can be added to inpainting media to act as a binder for dry pigments or pastels, to adjust solubility and thus reversibility, to alter viscosity, and to adjust gloss. Coatings may be applied over inpainting to seal media or adjust gloss. See Adhesives for Paper for description of characteristics, stability, and preparation of the following materials.
Gums: Historically used by artists, but not generally used by conservators because of tendency to crack when heavily applied. May be used to attempt to match gloss of original gum coating.
Acrylic Dispersions: Liquitex Acrylic Gloss Medium and Varnish, acrylic dispersion adhesives (Rhoplex, Plextol, Lascaux, etc.).
Application tools: Cotton swabs, blotters, sponge pastel blenders, erasers (manual and motorized), wooden skewers, cotton, tortillions and stumps, polyester film (Mylar), toothpicks, absorbent dental tips (Healthco), air brush, drafting masks.
Palettes and Mixing Equipment: Ground glass, unglazed ceramic dishes, sandpaper, aluminum pans, beakers, small pieces of glass or plexiglas, disposable paper palettes, plastic pans.
Burnishing Tools: Bone folders, small Teflon spatulas, agates, curved dental tools, fingernail, cotton swabs, polyester web, Japanese tissue.
Order of Treatment Procedures: Inpainting is one of the last procedures to be carried out during treatment of an object. Wet treatments, stain removal, etc. should be undertaken before inpainting. If flattening is the final procedure, the object should be humidified and dried so as not to disturb inpainting.
General Working Tips: During treatment, review inpainting in several lighting situations (incandescent, natural, fluorescent; specular, raking, normal) and in both horizontal and vertical positions. Step away many times so visual considerations are fresh. Test on extra material from insert or similar paper. With translucent papers and repairs, consider what the work of art will be against (e.g., mat board); color of mat will affect color of support and insert. Also see Considerations During Inpainting.
Set down lifted fibers in abraded areas with moisture or adhesive (wheat starch paste, methyl cellulose, methyl cellulose/carboxy methyl cellulose mix, gelatin, etc.).
Damages (such as gouges) or irregular surfaces may need to be filled with paper fibers, cellulose powder, or other appropriate material before inpainting.
Err on the side of slightly lighter and cooler than surrounding color.
Relationship of warm-to-cool color matching is very important. Often building up a color by mixing (e.g., a cool blue with yellow to create a green) will be more successful than directly applying a single color.
One can create a color that will read as “dark” but not be as harsh as black by mixing dark blues, brown or red with black.
Build up several layers of the same or different colors to simulate the complexity of the artifact, rather than an obviously single color application.
Use of Complementary Colors (DDM): When toning an insert paper to match the base paper tone, it is often advisable to work using the principle of complementary colors. Utilizing complementary color pairs when selecting the color to apply gives one the ability to significantly alter the resulting color using very little amounts of toning medium. Keeping toning medium to a minimum helps maintain the translucent quality which is so important in replicating a convincing paper tone. For example, if a paper is becoming orange-brown, instead of adding a darker brown to compensate, add a very thin wash of a blue (or terre verte). An extremely small amount of blue is all that is required to neutralize the orange tone and the resulting color appears more natural and less like a painted surface.
Do not overwork the area as colors can become muddy and less convincing.
Dry Media in Stick Form: Pastels, charcoal, crayons, etc. can be applied directly; however, because of their chunky form and often friable nature, they tend to be applied in powdered form using brushes, etc. (See Crumbled Dry Media under Application of Dry Materials). In stick form, they are used more often for toning inserts where they are applied directly and then blended with fingertips, swabs, brushes or stumps. Application tools/sticks can be formed to a point using knives or sandpaper.
Dry Media in Pencil Form (pastel, colored, charcoal, and graphite pencils): Pencil media can be applied directly to losses and inserts. Are easy to apply, controllable, and blendable. Colored pencils are fairly containable, do not penetrate into paper, and can be burnished to a high gloss. Sensitivity to water and organic solvents is dependent on type, brand, and specific color composition of pencil.
Dry application: Crumbled pastel sticks, scraped colored pencils, and dry pigments can be mixed in a container or on a palette, sheet of sandpaper, or paper/blotter to form powders of the desired color. Palette made of ground glass or masking tape strip on glass provides for slight tooth without losing all color into absorbent blotter. (JW) The mixture is applied with pointed or stipple brushes, absorbent tips (Healthco), swabs, stumps, blotter tips, toothpicks, etc. Excess powder can be removed with swabs or brushes, dry or moistened, or can be picked up with kneaded erasers.
Dry application: (AD) Locally “humidify” or moisten area so dry media can be held while it is being manipulated and not smudge adjacent areas. (Note that the paper is not wet.) Alternatively, apply a thin layer of methyl cellulose or gelatin to the area. Stipple on color in a series of thin coats using a pointed or stipple brush. Burnish with Japanese tissue (Uda) or Hollytex, and cover with a weight until dry. Repeat until color and density is appropriate. A final thin layer of methyl cellulose or gelatin may be applied, but generally is not necessary.
Wet application: Pastels, dry pigments, and powdery colored and graphite pencils can be mixed with a damp brush, water, ethanol, or binders such as methyl cellulose, gelatin, acrylic resin or dispersion, polyvinyl acetate resin, etc. Better color buildup may be achieved with wet application than when powdered media are applied dry. Variations in gloss depend on the type and amount of binder.
Powdered pastel colors can be also easily blended in wet condition to achieve a particular tone. Check dried color first before application. Useful for inpainting small blemishes on pastel paintings. Addition of small quantity of ethanol to pigment mixture will facilitate transfer of pigments onto support (especially when pigments will not adhere to the paper well). Working with ethanol as a carrier facilitates color mixing and application, and inpainting dries quickly. Be aware of danger of wicking water/ethanol into surrounding areas. Check ethanol compatibility of pigments.
Wet Application of Colored Pencils: Water-soluble colored pencils can be applied dry and then brushed over with water, or the tip dipped in water and applied damp for ease of application and to achieve intense color. (HK) Colored pencils can be applied similarly using mineral spirits, etc. instead of water.
General Techniques: The following techniques can be used for toning inserts as well as for inpainting.
Watercolors, inks, and other paints may be diluted with appropriate solvents and applied directly with small brushes. Applying wet media with a fairly dry brush by touching the brush on blotting paper may prevent wicking of media by paper substrate.
Wet inpainting media can be selectively picked up with dry or moistened blotter tip or swabs to soften or blend toning. Erasers can be used to lighten watercolor when already dry. Care should be taken not to alter the original surface when working directly on an object.
Wet media, such as acrylic emulsion paints and watercolors, change color when dry.
Reversibility of wet media is increased by the presence of an isolating layer and/or by the addition of a large molecule resoluble gum, such as methyl cellulose or carboxymethyl cellulose.
Considerations relating to transparency of watercolor pigments: Organic pigments tend to be transparent, inorganic pigments from metals tend to be opaque. However, some transparent colors have high tinting strengths and can stain the paper and overpower underlying colors (e.g., alizarin crimson has high staining power). (Weingrod, 1991, 15) Opacity may be more easily achieved with gouaches than with repeated layering of transparent watercolors.
Watercolors can be applied in a single layer or in several layers utilizing the transparent nature of some pigments to create a third color.
It may be difficult to achieve dense or dark passages by layering watercolor washes due to tendency of previous layers to be picked-up by damp brush. Acrylics can be layered more successfully.
Some watercolor pigments “settle out” when mixed in dilute solutions. Frequent stirring helps maintain a well-blended mixture.
Pastels or kaolin may be added to watercolors to increase matte appearance.
Alternating layers of colored pencils and watercolors have been used to build up dark or opaque passages, and to simulate some printing inks.
Acrylics can change color when dry and tend to appear opaque unless thinned with water.
Adjusting Diluent (JB): Behavior and handling of inpainting media can be modified by adjusting the diluent formulation. For watercolor media, acetone may be added to replace a portion of the water in the diluent (i.e., 20% to 60%) to produce paints with speedier evaporation and less tendency to travel. For solvent-resin acrylics, slow evaporating solvents, such as xylene, may be used for long working times; speedier mixtures, incorporating benzine and acetone (or toluene, although to be avoided for its noxiousness) will produce faster evaporating inpaint. Faster evaporating mixes may be helpful for brush recreation of crisp, “high-standing” printed intaglio ink lines.
Flat tones on large inserts may be achieved before final shaping and attachment to the object by using an airbrush with diluted watercolors, acrylic paints, inks, etc. Areas not to be toned can be masked. Practice is required to control dripping and unwanted spray from airbrush. Also, splatter effect on lithographs can be simulated using airbrush.
Increasing Surface Gloss: An inpainted area or insert paper can be burnished with the tip of a bone folder, teflon spatula, stainless steel dental tool, or agate directly rubbed on the surface or with a barrier of polyester web, slick paper (i.e. silicone release paper, gampi tissue), polyester film, etc. to increase gloss. Buffing with cotton pad or swabs may also increase gloss. Burnishing is often accompanied by a decrease in surface texture which may or may not be desirable.
See Extenders, Fillers, and Matting/Flatting Agents under Pigments for discussion of microballoons, silica, chalk, etc.
To increase gloss or simulate a coating, inpainting can be coated with gelatin, methyl cellulose, gum arabic, acrylic resin or emulsion, microcrystalline wax, etc. Caution should be exercised, since application of coating may disturb or lift inpainting. Coating can be burnished to increase gloss.
Achieving High Gloss: If high gloss is required on insert paper, silicone release Mylar can be placed on coating while wet and the area put under weight until dry. Especially effective with Liquitex acrylic medium or acrylic dispersion adhesives (i.e., Rhoplex, Plextol). If necessary, repeat to get even gloss. This technique may be problematic if used directly on an object as coating material may seep beyond the desired area when heavily applied.
Erasers: White vinyl, gum, and kneaded rubber erasers can be used to pick up dry media and lighten dried watercolors. However, pigment particles may remain in the interstices of the paper substrate.
Mechanical Removal: In some cases, one may be able to gently scrape off inpainting with scalpels and pick up the particles with a kneaded eraser. This technique may cause less embedding of inpainting media into the paper than removal with moisture.
Removal of Colored Pencils: Colored pencils can partially be reduced with eraser, scalpel, etc. Damp swabs may be used to partially lift off colored pencil, however, too much moisture may set colors or cause bleeding of media. Removal is most effective when an isolating layer or size is present. However, if heavily applied or applied wet, colored pencils can be difficult to remove. Be aware that some colored pencils are soluble in water, while some are sensitive to organic solvents, and others may be affected by both.
Paper fibers, teased from either Western or Japanese papers and toned to match support or media, can be adhered with methyl cellulose or wheat starch paste.
Overlays: Inserts or overlays may be used to cover stains or reconstruct design where inpainting may not be successful or desirable. In some cases, these may be more reversible than inpainting. However, there is no guarantee that the color of the overlay will remain matched to that of the paper support after aging.
Custom-mixed paper pulp discs can be made and then used for inserts or overlays. See Filling of Losses.
Toned Supports: Mat board beneath loss can be toned with watercolors, or toned inserts can be adhered to the mat to visually compensate for losses. The combination of toned and white mat board (or paper inserts) can visually integrate discolored and unaffected areas of a fairly translucent paper, thereby delaying or avoiding treatment (i.e., stain removal, washing, or inpainting).
Serigraph Ink: Pigments ground in microcrystalline wax are very good for filling chip losses in serigraphs and clay-coated papers; areas can be burnished to match sheen.(HK) Acrylic or polyvinyl acetate paints have been used to replicate screen inks.
Gouache: Pastel pigments may be applied with a wet brush to replicate matte gouache in small areas. Superficial scratches in gouache can be gone over lightly with a damp brush to restore original surface characteristics instead of inpainting.
The amount of anticipated reduction of the visual strength of a stain should be considered as should its dimension. The degree of subtle application of inpainting media is important.(DDM) Some stains may be successfully diminished, but in other cases inpainting may be more distracting than the appearance of the original stain or damage.
Disguising with paper fibers or temporary inserts may be options. See Removal of Inpainting and Alternatives to Inpainting.
ASTM (American Society for Testing and Materials) classifies the following pigments as having excellent lightfastness (category 1): burnt sienna, burnt umber, raw sienna, raw umber, Prussian blue, cerulean blue, cobalt blue, ultramarine blue, ivory black, lamp black, terre verte, viridian, yellow ochre, most cadmium pigments, red oxide, Chinese white.
Manufacturers' Classifications: For example, Winsor & Newton classifies all its paints in terms of permanence judging them on durability and lightfastness in under glass, are exposed to ordinary daylight, damp, and atmospheric pollutants for a number of years. (See product literature.) Classification designations (AA extremely permanent through C fugitive) are marked on the paint tube. Some of the pigments classified as category 1 by ASTM are marked only as class A by Winsor & Newton: cadmium reds and yellows, ultramarine blue, and Prussian blue.
Published Guides: The Wilcox Guide to the Best Watercolor Paints gives descriptions of pigments, paints, and particular manufacturers' products. Wilcox rates each tube of paint based upon reliability, suitability, and quality. ASTM lightfastness classifications also given. Since Wilcox's definitions are not clearly explained, take care when interpreting ratings of paints.
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