Paper, Ink and Printing
ACID FREE v. ARCHIVAL PAPER
INKJET v. LASER v. GICLEE PRINTING
TRADITIONAL v. MODERN INK
ORDINARY v. MUSEUM QUALITY PRINTS
As printmakers in the 21st century, we've been hearing these terms for years. The process of fine art print making in the 21st century is different from that of the 19th or 20th in that no longer are prints exclusively made using offset or screen printing processes.
"Museum quality" prints are produced using highly technological devices that spray sophisticated, pre-manufactured ink through complex, electrically driven devices that lay the ink onto paper which has undergone extensive pre-treatment, all to help bring out the colors of a print as true to the original as possible.
You wouldn't know this by looking at prints bought online or those made with a desktop printer. But I'd like to describe these complicated and labor intensive processes, the same we employ in making archival reproductions from originals.
After over a decade in the business, we’ve come across a range of articles, papers, and statements, written from various perspectives which describe these processes. The sources include: artists, museums, entrepreneurs, printers, ink and paper manufacturers, research centers, conservationists, government standards declarations, et al.
We've often thought this information should be condensed into concise terms, in a single document, so a layman contemplating the purchase of an "archival" or "museum quality" print can understand the range of processes and competencies that go into creating such a work. Such information is useful because it also details how museums and artists implement these processes when reproducing their own works for sale. Fittingly, the Library of Congress, the source of the images offered for sale, has made some statements about these various issues too.
1. ACID FREE v. NON ACID FREE PAPER
2. ARCHIVAL v. NON ARCHIVAL PAPER
3. THE STRUCTURE OF WORKS OF ART ON PAPER
4. MODERN DIGITAL PRINTING
5. DIGITAL INK PRINTING - HEAT v. VIBRATION
6. LASER PRINTING
7. INK TECHNOLOGY FOR INKJET PRINTING
8. GICLEE PRINTING
9. MEDIA TYPES
10. RESIN COATED v. FIBER BASED PAPER
11. SPECIALTY ARCHIVAL PAPERS
12. ARCHIVAL INKS
ACID FREE v. NON ACID FREE PAPER
Paper is one of the starting materials for creating a work of art. This article from Wikipedia sums up the discussion of acid free v. non acid free paper. Accordingly, "paper made from wood-based pulp that has not had its lignin removed turns yellow, becomes brittle and deteriorates over time." (Lignin a key structure in vascular plants involved in the formation of cell walls.) Various processes have been developed to render wood pulp acid-free ensuring the resulting paper made will last over 100 years. The article notes that alkaline papers made today, which account for most commercial papers used in the marketplace, may have a life expectancy of between 500 – 1,000 years.
The U.S. Government developed a voluntary standards system in 1984 to deal with issues such as paper pH, tear resistance, alkaline reserve, and lignin thresholds. The standards were developed by librarians concerned about long term document preservation. Manufacturers of acid-free paper can alert the public of their compliance with the standards (called "ISO 9706" or "ANSI Z39.48-1992") by using a circled infinity symbol.
ARCHIVAL v. NON ARCHIVAL PAPER
"Archival paper is an especially permanent, durable acid-free paper meant to be used for publications of high legal, historical or significant value. In the USA, such paper must also be approved in accordance with the ANSI standards." Instead of using wood-based paper, cotton rag is used for archival paper production. Further, "archival paper is sometimes broken down into two categories:
Conservation-grade – acid free, buffered paper made from wood based pulp.
Archival-grade (Museum-grade) – cotton rag paper made from cotton pulp."
THE STRUCTURE OF WORKS OF ART ON PAPER
A scholarly article written by Mary Fahey, Head of Preservation/Chief Conservator at the Benson Ford Research Center entitled, "The Care and Preservation of Documents and Works of Art on Paper" discusses this subject.
The article defines "most paper items (as) consist(ing) of three basic components: the paper support, a sizing material or ground, and the media that is used to create the document or work of art."
Paper was handmade prior to the 19th century and "consisted of cotton, hemp, linen or mulberry fibers". These papers were called rag paper and were expected to last hundreds of years.
Wood based papers made their appearance in the 19th century in newsprint and magazines and are prone to rapid degeneration due to the acid based properties of lignin described above.
"Sizing refers to the application of adhesives such as gelatin, plant gums and starches to the surface of a sheet of paper" used to make the paper "less absorptive in order to prevent the bleeding and blurring of media". Sizing also adds strength to the paper. The use of chalk, clay or other materials may also be added to the paper giving it more smoothness.
"Media refers to the materials that have been used to create the work of art itself." (ie, watercolors, pencil, chalk, pastel and Conte crayons). Various factors influence the integrity and degradation of a work of art. Handling (physical handling as well as oils and salts from the human hand) and environmental factors (pollution, pests, temperature, humidity and light) are key in this process. Proper storage, exhibition, matting and framing of artworks are also important factors in long term preservation.
MODERN DIGITAL PRINTING
A very technical book was put out in 2005 by Smart Papers (a paper manufacturing company) called "Today's Digital Imaging v5.0". The book states that "by 2010, 99% of all printing will occur on a digital device," and it has a large amount of useful information regarding the entire modern digital printing industry.
"Photo printing by color inkjet devices, laser printers, and copiers (meets) or even surpasses the quality of silver halide prints, enabling color printing to enter markets previously closed to digital printing like medical imaging, photo studios, mapping, catalogs, books and flyers."
The book reminds us that Johan Guttenberg was the first to use letterpress printing when he reproduced a copy of the Bible (15th century). "Prior to this, all books were handwritten by scribes. Color process work was initiated in the 1880s just after web presses which were introduced in the late 1870s. From there Silk-Screening, Gravure, Flexography, and Offset Printing (1906) were also developed. It wasn't until the mid-1970s that the first use of computers in the pressroom took place."
Since that time, five different types of printing technologies have emerged: laser, liquid inkjet, solid ink, dye sublimation, and thermal wax. You can refer to the book for a discussion of the latter three of these methods. This essay will refer to the book's discussion of the first two methods, laser and liquid inkjet technology.
DIGITAL INK PRINTING – HEAT v. VIBRATION
According to Smart Papers, "there are two types of inkjet printers – thermal and piezoelectric.
In thermal inkjets, the printhead contains four ink cartridges, within each of which is an ink filled firing chamber. An electrical current runs through resistors at the bottom of each chamber, causing a vapor bubble to form. The bubble expands pushing the ink droplet through the nozzle and onto the paper. The resistor then cools, causing the bubble to burst, and fresh ink is sucked into the firing chamber for the next ink droplet.
Instead of resistors, piezoelectric inkjets (a process patented by Epson) have a thin layer of crystal between two electrodes, and each printhead nozzle is contained within a piezo crystal. An electric current causes the crystal to vibrate and squeeze ink out of the nozzle onto the paper."
A laser based printer is a high end device used for making fine art prints. The costs for these printers can range into the hundreds of thousands of dollars and they can produce some of the most beautiful fine art reproductions given their complex technological processes.
Smart Papers has this to say about laser based printing. "With these printers, jobs are sent electronically to the printer. The printing files are either sent as PostScript files or are converted by the printer to PostScript. PostScript is a computer-encoded file that includes instructions for the computer to print the image. It is then translated by the Raster Image Process (RIP), which converts the instructions into a bitmap or the actual pattern of dots needed by the printer to image the pages. This is commonly called 'RIPping' and all files must be 'RIPped' before the HP Indigo can process it.
The Photo Imaging Plate (PIP) on the drum rotates and is electronically charged by the Ione Scorotron Unit. It is then discharged by the Writing Head laser beam as it scans the PIP, applying one color separation per rotation. The image has a voltage of (minus) –50 volts and the background (non-image) is charged at minus –700 volts. The laser does not burn an image permanently onto the PIP; it burns a new image with every full rotation of the drum. The ink particles are 2 – 4 microns in size and are mixed, heated and transported through the use of a viscous fluid called Imaging Oil.
The injectors spray ink Y (yellow), M (magenta), C (cyan) or K (black), into the gap between the PIP drum and the Developer Drum, where the ink is either attracted to the Developer Drum or the PIP. Due to the conductivity differential between the image and the background, the ink in the background is repelled and sent to the Developer Drum, while the ink remains on the image area of the PIP.
The Developer Drum is not synchronized with the PIP drum and excess ink from the background (non-image) area is removed from the gap. The wiper blades remove the ink to a catch basin, where the Imaging Oil is separated from the ink for reuse. The Reverse Roller cleans off excess ink particles that may have been attracted to the background areas of the PIP.
A squeegee electrically compresses the image onto the PIP and removed up to 60% of the Imaging Oil. The Pre-Transfer Erase (PTE) lamp discharges a high electrical charge on the PIP, without affecting the ink image. The PIP is in contact with the Intermediate Transfer Media (ITM) drum, which contains the blanket that has been heated and charged at + 650 volts. The positively charged blanket attracts the negatively charged ink image and the image is transferred from the PIP to the blanket for the initial transfer. The heated ITM blanket melts the ink particles into a viscous layer. Some papers are treated with a Sapphire coating, which is a clear surface coating that allows the ink to bond. The paper transport feeds a sheet of paper to the Impression Drum (IMP), which is help in place by gripper. The ITM drum and the IMP drum blanket are in direct contact under pressure. As they rotate, the melted ink image on the ITM solidifies and adheres to the cold paper; this is the second transfer. Less than 10% of the Imaging Oil is left at this point. The complete cycle listed above is repeated for color separation. The paper remains gripped until all of the desired colors (separations) are transferred. This process can render a very high resolution print – up to 800 dpi resolution. It involves a 4 color process and can include a maximum of 3 special colors – a wide color gamut.
INK TECHNOLOGY FOR INKJET PRINTING
Smart Papers notes that "the design of inks for inkjet applications is a complex process. Inkjet inks must exhibit excellent color properties and image details. Ink formulations must be compatible with print cartridge components and materials as well as how the cartridge functions. The ink also needs to interact with the coating chemistry and properties of the media used for printing.
Most ink used in inkjet technology is water based. Ink color can be achieved with pigments or dyes. Other main ingredients include surfactants, humectants, corrosion inhibitors, biocides, and other additives. Humectants are important to prevent the ink from drying out and clogging the nozzles of a printhead. The way in which an ink flows on a medium can be modified with various surfactants.
Color gamuts are obtained using combinations of Cyan, Magenta, Yellow, and Black ink. Inkjet systems now include additional cartridges with inks designed specifically for photo printing, thereby expanding the color gamut. Six or eight color ink cartridge systems are available for use in specialty inkjet photo printers.
The wide gamut of colors available is also suitable for the depth of coloration involved in fine art reproduction printing as well. Such printing is called "Giclee" printing and is described further below.
Important physical properties of inkjet inks include viscosity, surface tension, pH, and conductivity. UV-Vis Spectrophotometry is used to measure the color intensity and absorption spectra of inks and colorants.
Viscosity helps control the flow and release of the ink. Proper ink flow is important for droplet size as well as how the ink flows onto the media. The viscosity will also affect the drying characteristics of an ink. Lowering the surface tension helps improve the wetting characteristics which in turn determines the image sharpness and prevents color mixing or bleed.
PH and conductivity are important to control to assure the ink is compatible with print head materials and imaging media. Colorant stability becomes a critical issue when evaluating the permanence of a printed image.
Interaction between ink and media is another complex area. Media for inkjet applications is becoming highly specialized with its own set of critical properties. Ink properties must be coordinated with media properties to prevent bleeding, smearing, cockle, or curl.
Inkjet media can be classified as two categories: microporous and swellable. Both are multi-layers of polymer based coatings. The different coating layers are used to provide a range of gloss and finishes, to improve light and stability and moisture resistance, and to optimize the color gamut. Important specifications for media including the following: brightness, caliper, weight, gloss level, moisture, shade, and opacity.
Dye based and pigment based inks will behave different only the two types of substrates. Dye based inks will exhibits very fast capillary action into microporous media. The dyes will penetrate into the layers of the coating providing stability and thorough drying. On swellable media, the dyes will stay closer to the surface and take longer to dry.
Pigmented inks will penetrate slightly into a porous coating. On a swellable coating, the ink vehicle absorbs into the coating polymer, but the pigments stay closer to the surface. Generally, pigmented inks dry slower than dye based inks on coated media.
Two types of inkjet technology are thermal and piezo. Thermal inkjet involves heating a small volume of ink causing it to vaporize and expand. The ink droplets squeeze through the nozzle of the print cartridge. Piezo inkjet technology involves sending an electronic charge to a piezoelectric crystal causing it to vibrate. The vibration forces the ink droplet to move through the print head nozzles. The printhead scans the pages in horizontal strips of the image. Inkjet systems must combine the printhead technology, the ink formulation, printer software, and media to create a digital image.
A buzzword of the industry in the 1990s was the term "Giclee". It comes from the French word "gicleur" which means "jet" or "nozzle" (and the verb gicler means "to squirt, spurt, or spray").
Generally, making a Giclee print involves doing more than just printing out something on a desktop printer. It involves printing using a 6-12 color, high end, large format printer and the use of archival paper and inks.
Giclée is a neologism coined in 1991 by printmaker Jack Duganne for fine art digital prints made on inkjet printers. The name originally applied to fine art prints created on IRIS printers in a process invented in the late 1980s but has since come to mean any inkjet print. It is often used by artists, galleries, and print shops to suggest high quality printing but since it is an unregulated word it has no associated warranty of quality.
Besides its original association with IRIS prints, the word Giclée has come to be associated with other types of inkjet printing including processes that use fade-resistant, archival inks (pigment-based), and archival substrates. These printers use the CMYK color process but may have multiple cartridges for variations of each color based on the CcMmYK color model (such as light magenta and light cyan inks in addition to regular magenta and cyan); this increases the apparent resolution and color gamut and allows smoother gradient transitions. A wide variety of substrates is available, including various textures and finishes such as matte photo paper, watercolor paper, cotton canvas, or artist textured vinyl.
The website "Archival Maps" notes that
Giclee is known for its brilliant color range and depth and its ability to capture the finest details of an image. The Giclee method involves a process of spraying tiny droplets of ink onto archival paper to produce a deeply saturated rich quality print that captures the actual look and feel of the original. Giclees are superior to traditional printing methods in several ways: the colors are brighter, last longer and are so high resolution that they are virtually a continuous tone rather than tiny dots.
A noted artist/sculptor Wim Griffith says the following about Giclees:
Each calculation of hue, value and density direct the ink from four or eight nozzles. This produces a combination of 512 chromatic changes, with over three million colors possible. This highly saturated, non-toxic, ink produces the rich opulent color of the original with its artful nuances. No screens are used in this process. The resolution of the digital print is higher than traditional lithographic print and has a wider color gamut than serigraphy. Giclée prints render deep, saturated colors and have a beautiful painterly quality that retains minute detail, subtle tints and blends. Every brush stroke of the original painting is apparent.
Griffith goes on to say:
Giclée prints have an impressive exhibition record. They have been shown in museums and galleries throughout the world. Dozens of museums have mounted exhibitions or purchased Giclees for their permanent collections. These include The Metropolitan Museum (New York), the Guggenheim (New York), the Museum of Fine Arts (Boston), the Isabella Stewart Gardner Museum (Boston), the Philadelphia Museum, the Butler Institute (Youngstown, OH), the Corcoran (DC), the National Gallery for Women in the Arts (DC),the Kennedy Center for Performing Arts (DC), the Walker Art Center(MN), the Smithsonian Institution Libraries, the New York Public Library Print Collection, the High Museum (Atlanta), the California Museum of Photography, the National Museum of Mexico and the San Jose Museum, among others.
Lastly, Willhelm Research is an Iowa company that conducts research on digital prints. According to their site:
Wilhelm was a founding member of the Photographic Materials Group of the American Institute for Conservation of Historic and Artistic Works, is a member of the Electronic Materials Group of AIC, and was a founding member of American National Standards Institute/ISO subcommittee IT9-3 (now called ISO WG-5 Task Group 3), which is responsible for developing standardized accelerated test methods for the stability of color photographs and digital print materials. He has served as Secretary of that group since 1984, and is an active member of the ANSI/ISO subcommittees responsible for storage standards for black-and-white films and prints.
Willhelm is a leading expert on digital print making and you can read more about them on their website (willhelm-research.com). The Willhelm site contains a vast array of articles discussing the permanence of digitally made prints and inks as well as associated printing technologies.
Many leading media suppliers offer media for both technical and graphics applications. The range of media offered by leading media suppliers includes:
- Photograde media
- Glossy & Matte coated papers
- Clear film
- Backlit film
- Vinyl (Scrim & Adhesive-backed)
- Typical technical document and graphics media sizes are 24, 26, 42, 50, 54, 60 and 72" wide
RESIN COATED v. FIBER BASED PAPER
Resin v. Fiber is an important contrast to be aware of when it comes to the subject of papers used by photographers.
A terrific article which outlies this debate was found on the website hubtz.com.
RC vs. FB (Resin-Coated versus Fiber-Based Paper): The Debate Rages On
"Over 99.5% of all the photographs produced today are produced on Resin-Coated paper. A high cotton-content paper is first coated with a plastic resin. Then, a light-sensitive emulsion is placed on top of one side. After the paper is exposed to the image under an enlarger, the paper goes through a four-stage wet developing process: develop, stop-develop, fix, and wash. The cotton fibers underneath the resin coating remain dry throughout the entire process.
"Fiber-based papers lack the resin coating, which sparks off the much-heated debate, 'Which one is better?' Without the resin coating, the light-sensitive emulsion becomes saturated in the cotton fibers and gives the image on the paper more depth. When placed side by side with resin-coated papers, fiber-based papers produce a richer image under identical development.
"In preparation of fiber-based paper, development time is doubled to allow the developer to activate the deeply-embedded light-sensitive emulsion. Fixing time is usually doubled, and requires a double-fix bath and depletes the fixer bath about five times faster. Washing time needed to remove the fixer increases by a factor of ten. Archival agents need to be introduced during the wash to remove the fixer from the cotton fibers. When fiber-based paper is allowed to dry in the open air, the emulsion side will dry at a different rate than the opposing side. Single-weight papers will curl into a tight scroll and become hopelessly disfigured. Double-weight papers will scroll significantly less, but become hopelessly rippled and will never lie flat.
"A special paper dryer is used to flash-dry fiber-based papers. The most common type of dryer is a curved, stainless steel plate with a removable canvas cover. The wet prints are sandwiched between the steel plate and the canvas, while a precise amount of heat is applied to quickly remove the water, forcing the paper to dry flat.
"To mount a fiber-based photograph onto a piece of mat board, linen tape is used to hold the print down. The ugly tape must be hidden underneath a covering over-mat. Since the size of each print will vary slightly, the over-mat must be custom-ordered and cut to size at this time. The process to mount Resin-coated papers differs greatly. These papers are mounted with a quick, heat-activated adhesive. Since the adhesive is completely hidden beneath the image, a 'floating' over-mat is used, which does not have to cover the edges of the photograph. These mats can be pre-cut and stocked for all 11x14" photographs. A debate rages on about the archival properties of resin-coated versus fiber-based papers. The debate is not easily resolved, since archival times are measured in hundreds of years. Over the course of centuries (hundreds of years), it has been claimed that the plastic resin emits a corrosive gas which will degrade or destroy the emulsion. The opposing side debates that resins produced in modern photographic papers will not emit this gas. (A similar debate rages on about the archival properties of Compact Discs.) However, by eliminating the resin coating completely in fiber-based papers, the cotton fibers can be saturated with trace amounts of fixer chemicals, which, if present, will degrade the image much quicker than plastic resin gases.
"Fiber-based papers have been used as a status symbol among photographers to justify themselves as 'artists' as opposed to 'shutterbugs'. Photography as a work of art has been steadily loosing ground with the introduction of computerized camera equipment and 20-minute photo labs. Producing a photograph on fiber-based paper is akin to hand-painting on a canvas (and often takes as long).
"The turn-around time for a fiber-based print is longer and the price is more expensive."
SPECIALTY ARCHIVAL PAPERS
According to a fine art printing advisory website, InkJet Station, archival paper is referred to as "Museum Grade" (ISO Standard 11108) and it means the following:
- The paper is acid free with a pH value between 7.5 and 10
- The paper has an alkali reserve of at least 2% calcium carbonate
- The paper is resistant to tearing
- The paper is free of easily oxidized material, or lignin
- The paper is made from cotton
- The paper has a high endurance to breakage by folding
"The ISO 11108 and 9706 standards and their predecessors, including NISO ANSI Z39.48-1992 and NISO ANSI Z39.48-1984, were established to provide criteria for paper to last several hundred years in libraries and archives in order to reduce problems these entities face in preserving important works. ISO Standard 9706 sets forth the first four requirements above to certify a paper for permanence, while ISO 11108 adds two additional requirements for archival quality. Archival quality papers are significantly stronger than permanent papers, can withstand more handling, and will last longer.
The United States Library of Congress sets forth even stricter standards than ISO 11108 for archival papers. The Library requires a stricter pH between 8 and 9.5 and requires the paper be free of optical brightening agents. The Library further requires papers to pass a Photographic Activity Test performed by Rochester Institute of Technology's Institute of Paper Permanence. This test certifies that the paper does not fade or bleed, and passes strict metallic impurities specifications to avoid damage to photos and documents they come in contact with."
Guidelines to HP Paper
- All HP paper and print media and their packaging do not contain asbestos or heavy metals.
- Manufacturing processes for paper, print media and their packaging do not use ozone depleting substances.
- All HP paper and print media and their packaging comply with chemical registration and premanufacture notification requirements in countries the products are sold.
- Most HP paper and print media is made with elementally chlorine free processing.
- None of the HP transparency products contain PVC resource conservation.
- All uncoated small format office paper (except brochures), greeting cards, glossy paper, and photo paper do NOT contain virgin wood fibers derived from old-growth forests.
- HP office recycled paper contains 30% post consumer recycled content paper fiber.
- All HP transparencies contain 45% recycled content. It is a mixture of pre-consumer and post-consumer recycled material. The percentage changes for both, and, therefore, cannot be specified.
- HP Felt Textured Greeting Card / Ivory paperbase contains 30% post consumer recycled content paper fiber design for recycling.
- All uncoated office paper, greeting cards, and glossy paper are recyclable with normal office paper in the areas where such facilities or services exist.
Lastly, Marion Meissner, leader of Print and Test Services at ILFORD Imaging in Switzerland, has some things to say about the use of archival inks in the process of fine art printing. (Source: http://blog.ilford.com/category/technical-info/)
"Most current inkjet printers used in the photographic industry are pigment based ink sets. While dye ink sets produce a slightly larger color gamut, pigment inks produce high quality results with greatly enhanced print permanence.
"In the above illustration, it's easy to see that dye inks absorb into the receiving layer on the paper base while pigment inks remain on the surface of the media. Pigment inks are more archival but the tradeoff is some loss in color gamut (colors that can be reproduced). Dye inks have advanced in their stability and permanence over time and pigment inks have improved as well closing the gap with gamut reproduction so that most professional quality inkjet printers for photographers are pigment based."