Onionskin paper. Note the paper texture. Taken from an image of the ILIR Library Teamsters Contracts Vertical File, 1948-69 (35/3/415) from the University Archives. Image courtesy of the University of Illinois Board of Trustees.
Image/Text
Carbon-based ink; aniline-based ink (VERY COMMON)
Identification
Almost always a single color but may be of any color. Image/text appears faint and dull. Carbon copies are on a semi-translucent paper (e.g. manifold, onionskin); typewritten originals are on opaque plain paper.
Preservation
Color inks are dye-based. Are water soluble as well as light and heat sensitive.
Blue ink stencil copy. Taken from an image of the ILIR Library Teamsters Contracts Vertical File, 1948-69 (35/3/415) from the University Archives. Image courtesy of the University of Illinois Board of Trustees.
Image/Text
Carbon-based ink; aniline-based ink (VERY COMMON)
Identification
Printed on rough, porous plain paper. May appear similar to hectographs and spirit duplicates. Has clotted or spotty characters. Oil-based ink will produce an oily halo.
Preservation
Early color inks contain aniline dye. Are water soluble as well as light and heat sensitive.
Overall stable; preservation risk depends primarily on quality of support material.
Letterpress typographic print. Courtesy of the Illinois History and Lincoln Collections, University Library, UIUC, University of Illinois Board of Trustees.
Image/Text
Carbon-based ink; aniline-based ink
Identification
Difficult to distinguish from typed originals and from stencil copies, hectographs, lithographs, and spirit duplicates. Characters are embossed. Oil-based ink will produce an oily halo.
Preservation
Early color inks contain aniline dye. Are water soluble as well as light and heat sensitive.
Overall stable; preservation risk depends primarily on quality of support material.
Hectograph. Taken from an image of the ILIR Library Teamsters Contracts Vertical File, 1948-69 (35/3/415) from the University Archives. Image courtesy of the University of Illinois Board of Trustees.
Image/Text
Aniline-based ink
Identification
Typically "crystal violet" or blue ink with little to no embossment. Printed on bright white, smooth, glossy paper. May appear similar to spirit duplicates and diazo prints.
Preservation
Color inks are dye-based. Are water soluble as well as light and heat sensitive.
Avoid alkaline enclosures.
Copy paper usually contained gelatin or alum rosin sizing; high heat and humidity will cause accelerated deterioration (e.g. yellowing, embrittlement).
Spirit duplicate copies. Image courtesy of Ian Batterham.
Image/Text
Aniline-based ink
Identification
Characteristic "crystal violet" ink color (although blue or black were sometimes also used) displaying little to no embossment. Paper surface is typically smooth and glossy. May appear similar to hectographs.
Preservation
Color inks are dye-based. Are water soluble as well as light and heat sensitive.
Avoid alkaline enclosures.
Paper may be yellowed; image may be faded with low contrast.
Photographic Processes (Metallic emulsion on specially coated paper)
White text on black background. May have rough edges or odd dimensions as a result of being cut from a roll. Qualitatively similar to a negative photo print, it may exhibit silver mirroring.
Diffusion transfer copies. Image courtesy of Ian Batterham.
Image/Text
Photographic silver (emulsion)
Identification
Manufacturer’s backprint may be present on verso, which might also hold marks made by blotchy waterstaining or fingerprints. Cut corners are an identifying characteristic of Kodak papers. Specially coated paper is likely thicker than similar copy processes. Paper tone is light brown or gray/buff.
Preservation
Sensitive to light.
Oxidation may result in silver mirroring.
Residual chemicals may cause staining or embrittlement.
Dual spectrum copies. Image courtesy of Ian Batterham.
Image/Text
Photographic silver (emulsion)
Identification
Light blue flame emblem may be present on verso. Paper ground is pinkish or cream colored with dark-red brown or black image. Specially coated papers will vary from flimsy to bond weight.
Preservation
Sensitive to light.
Oxidation may result in silver mirroring.
Slight acidity of residual silver salts may cause yellowing of support paper over time.
Electrostatic Processes (Carbon black or CMYK toner)
Electrostatic Xerox copies. Image courtesy of Ian Batterham.
Image/Text
Pigment-based (carbon black) toner (VERY COMMON)
Identification
Monochromatic black, high-contrast image/text that appears to sit on the surface of the paper. Edges of original scanned document may be visible in margin of copy if not aligned exactly during copying.
Preservation
Overall stable; preservation risk depends primarily on quality of support material.
Laser print document. Note the absence of imaging/scanning artifacts.
Image/Text
Black or pigment-based color (CMYK) toner
Identification
Toner appears to sit on the surface of the paper. In contrast to electrostatic (Xerox) printing, laser printing is usually made square on the page. Does not typically exhibit artifacts from scanned documents.
Preservation
Pigment-based color inks are more stable than dye-based, but they should still be considered sensitive to water and light.
Overall stable; preservation risk depends primarily on quality of support material.
Iron gall ink copybook pages. Image courtesy of the Chicago History Museum: John Kirk letter book, John Kirk collection, vol. 3, from the manuscript collection.
Image/Text
Aniline dye ink; Iron gall ink (COMMON)
Identification
Thin, translucent paper.
Preservation
Aniline dyes and iron gall ink are unstable. Color inks are dye-based, water soluble, light and heat sensitive.
May be rendered brittle by iron gall ink.
May be printed on low-grade wood pulp paper treated with sulphuric acid, which can cause paper to be embrittled.
Thermofax. Taken from an image of the ILIR Library Teamsters Contracts Vertical File, 1948-69 (35/3/415) from the University Archives. Image courtesy of the University of Illinois Board of Trustees.
Image/Text
Leuco dye (composition varies due to patented chemistry)
Identification
Thin sheet, with discoloration on recto (front), white on verso (back). May be difficult to identify due to variety of ink colors and types of support papers.
Preservation
Yellowing, embrittlement, and image darkening occurs rapidly due to chemical paper coating even if kept in dark storage.
Sensitive to high RH; heat will catalyze paper darkening.
Shiny layer of white pigment (zinc oxide) layer coating the support paper. Copies made after 1977 will display the electrofax logo, a pale yellow outline of a cactus, on the verso (back).
Preservation
Zinc oxide coating may crack or flake.
Sensitive to heat and light; exposure will cause dye fading.
Typically full-color with no scanning artifacts. Unless printed from a scan, print matter will be square on page and typically exhibit no artifacts due to its computer-generated origin.
Preservation
Ink should be considered sensitive to water and light.
Overall fading of the image may occur from light exposure, especially of magenta ink.
Preservation risk largely dependent on type and quality of support material, which can vary widely.
