Art Materials - Media
The most permanent inks have traditionally been made from binders and carbon, usually derived from soot. The modern ink called India ink is made in this way, often with the addition of shellac to make it waterproof. Such carbon based inks are unlikely to fade. Many black inks in current use, however, are not carbon based, but are made from dyes and such inks may be vulnerable to light.
Some modern colored inks are manufactured with lightfast pigments rather than dyes, but many are not. Since the nature of the ink used in a given work of art is usually unknown to the framer, colored inks should be considered fugitive—they are not lightfast.
With blotters placed in a little water we tested seven black inks to see which were carbon based. Only the Higgins India ink second from the right in the bottom picture was clearly a carbon ink. (The Higgins ink at the very right was waterproof so we couldn’t apply this test)
Inks used in making prints, such as lithographs and etchings, are as likely to be damaged by light as other inks, depending on the colors used. Natural organic colors fade on exposure to light, but modern synthetic organic pigments are far more durable, as are colors made from inorganic substances. Many prints made before the twentieth century are notably sensitive to light, as are period posters and Japanese prints. Digital prints are discussed at the end of the Photographs section below.
Pastels and other loose media
Pastel, charcoal, chalk and even graphite are easily smudged, and may be so lightly bound to paper fibers that they are vulnerable to the static charge of acrylic glazing. Charcoal contains no binder at all and is therefore likely to be the most vulnerable. Chalk, graphite in pencils, and pastels are all made with binder such as clay, gum tragacanth or methyl cellulose. Despite the inclusion of binding materials, they all share with charcoal risk from abrasion and loss of material due to the static charge of acrylic glazing. Some organic pastel colors are light fugitive.
Fixatives are a poor solution for loose media. To the degree that they are effective they may muddy the colors and give the surface an uneven sheen. Some fixatives age poorly.
Watercolor, gouache, and tempera
Watercolors are more subject to fading than most other media. Some colors, those that are organic based, are likely to be damaged by light, both by visible light and UV.
Watercolor penetrates the paper, and dwells among the paper fibers. Gouache and tempera, on the other hand, are fixed to the paper surface. Since they form a rigid layer, gouache and tempera may crack and flake when their paper support expands and contracts with changes in relative humidity. One should be especially careful in handling a work made with either gouache or tempera to fully support the sheet and avoid flexing it.
Heavily applied oil paint can create permanent waves in paper. Furthermore, the oil medium in oil paint penetrates paper, often developing an oxidation "halo" around heavily painted areas. This halo will darken in time. Since linseed oil is acidic eventually it can cause the paper support to become brittle.
When applied heavily to paper, acrylics, like oil paints, may cause the paper to become wavy. The surface of acrylic paints often remains soft, especially in a warm environment, so acrylic paintings on paper should be set back far enough in the frame that they will not come into contact with the glazing. Acrylic paints may be more likely to bond to acrylic glazing than to glass, so special care should be taken to prevent their touching.
From the standpoint of preservation, photography can be considered as two distinct subjects: analog (“traditional”) technology and digital technology. In the paragraphs below we describe traditional, pre-digital photographic methods. Digital printing technology is altogether different and will be treated at the end of this section.
Photographs are complicated objects, and in some ways they are distinct from other works on paper. Standards for storing and framing works of art on paper apply to framing photographs as well, since any condition that threatens a work on paper is even more likely to cause damage to a photograph.
Some early photographic images were printed on glass (ambrotypes) or on metal (daguerreotypes and tintypes). They are often fragile and easily damaged. If the original case is still present it should be considered to be part of the photographic object. Loose tintypes can be framed as photographs on paper are framed.
The nineteenth century photographs that we usually encounter are albumen prints, which, because they were commonly printed on very thin paper, were often originally mounted to cardboard, which may be warped and brittle. Albumen prints are vulnerable to damage from high temperature and humidity as well as atmospheric pollutants. Exposure to low humidity can cause cracking of the albumen, and exposure to light, especially UV light, risks yellowing as well as cracking.
Gelatin Prints—Fiber-base and Resin-coated Papers
Gelatin, purified animal protein, supplanted albumen for photographic emulsions in the late nineteenth century. Until the 1960's most gelatin emulsion photographic papers were coated with baryta (barium sulfate) to give the paper a smoother, whiter surface. These fiber-base, baryta coated papers make excellent, long-lived prints, but processing them requires long fixing, washing, and drying times. Expansion and contraction brought on by changes in relative humidity may cause these papers to curl.
Resin-coated (RC) papers were developed for shorter development times and better dimensional stability. These advantages come at a cost. Resin-coated papers are vulnerable to UV light, and can be damaged by visible light as well.. Although the technology has improved since RC papers were first introduced, they are not considered to be as permanent as fiber-base baryta prints. Because of the relative instability of RC prints, archival printing of black-and-white photographs is only done on fiber-base papers.
There are several varieties of pre-digital color prints. The dyes in all of them are impermanent (with one exception, noted below). Some are more damaged by light, others by high temperatures or high relative humidity.
Chromogenic prints. The chromogenic process has been used for most traditional color prints (such as Agfacolor, Ektacolor, Fujicolor, and Konica color) These prints are unstable; they fade in the dark as well as in light.
Cibachrome and Dye Transfer Prints. Both have excellent dark-storage stability. More to the point, polyester Cibachromes (now named Ilfochromes), made with a dye destruction process are quite resistant to light fading. Dye transfer prints are more sensitive to light than Cibachromes.
Polaroids. In general, procedures for framing Polaroid “instant prints” are similar to those employed for other photographs. The safest way to present Polaroid photographs in a frame is with corner pockets.
Like other color photographs, Polaroid color photographs are sensitive to light, especially in the UV range, although the last versions were much improved over the first Polaroid prints. In 2008 Polaroid announced that it would discontinue production of instant film, but since then a Dutch group, The Impossible Project, has re-introduced it.
Digital inkjet prints
Inkjet printing has made rapid and extraordinary gains since its introduction in about 1990. The early printing inks were dye-based and not light stable; they are also sensitive to ozone and humidity. According to reports by Wilhelm Imaging Research, these early prints even when framed with UV filtering, had a life of only a few years. Within a decade however Hewlett-Packard, Epson and Canon had all begun developing printers and pigmented inks for some of which Wilhelm gives permanence ratings of over 200 years.
Digital inkjet printing technology is technically unrelated to traditional photographic printing, and continues to be rapidly changing. To learn more, and to keep in touch with new printers, inks and papers, check Wilhelm Imaging Research and the Image Permanence Institute.