Architectural reprography
Encyclopedia
Architectural reprography, the reprography
of architectural drawing
s, covers a variety of technologies, media, and supports typically used to make multiple copies of original technical drawing
s and related records created by architects, landscape architect
s, engineers, surveyors
, mapmakers
and other professionals in building and engineering trades.
Within the context of archival preservation, the custodians of architectural records must consider many aspects of identification and care when managing the artifactual nature of these materials. Storage containers, handling, paper and chemical compositions and interactions, ultraviolet light exposure, humidity, mold, and other agents of potential harm all interact to determine the longevity of these documents. As well, architectural reprographic drawings are often in very large formats, making storage and handling decisions especially complex.
in the second half of the 19th century, the field of architectural reprography—and the corresponding developments of photography
and mass-produced wood-pulp paper
—saw significant experiments and advances in technology. Beginning with major refinements in blueprinting processes in the 1840s, through the widespread adoption of diazotype printing after World War II, the design profession turned to analog architectural reprography to create accurate, to-scale reproductions of original drawings created on tracing paper, vellum, and linen supports. These copies were typically used throughout the architect’s own design process and also for distribution to clients, contractors, governmental agencies, and other interested parties. However, the integration of CAD—or Computer-Aided Design
—over the last twenty-five years of design practice has made analog reprography far less common in the profession and more ephemeral in nature. For archivists, curators, librarians and other custodians of architectural records, traditional reprographic formats are now often seen as historic documents, with attendant needs for long-term care and conservation.
or Prussian blue
ground. To make a blueprint, a heavy paper (or more rarely drafting linen
) support is impregnated with potassium ferricyanide
and ferric ammonium, placed under a translucent original drawing, weighted with glass, and exposed to ultraviolet light. After sufficient light exposure, the glass and original drawing are removed and the blueprint paper is washed to reveal a negative image. This same process, using an intermediary reprographic drawing, could also be used to produce a positive blueprint—blue lines on a white ground—however, this more expensive and time-intensive method was far less commonly employed.
The major disadvantages of the blueprint process, however, included paper distortions caused by the wet process which might render scale drawings less accurately, as well as the inability to make further copies from the blueprints. Nonetheless, for its efficiency and low cost, the blueprint process, further simplified and mechanized by the turn of the 20th century, became the most widely-used reprographic process between the mid-19th century and the latter half of the 20th-century.
In archival settings, because the process involves ammonium
, the resulting prints should not be stored in contact with other papers that have a buffered reserve, nor should blueprints be de-acidified, as the resulting chemical interactions can cause irreversible image loss. Blueprints are also highly light-sensitive and should not be exposed to ultraviolet light for long periods of time.
salts suspended in a gelatin emulsion, placed under a translucent original drawing, weighted with glass, and exposed to ultraviolet light. As with the blueprint process, after sufficient light exposure, the original drawing is removed, the paper washed in a ferrocyanide
bath, and then rinsed in an acidic bath to reveal a positive image. This process required fewer steps than creating a positive blueprint, and was thus more widely employed during the late 19th and early 20th centuries.
In an archival setting, Pellet prints should be treated and stored under the same conditions as blueprints.
bath.
In an archival setting, Van Dyke prints are relatively rare, as they were created for temporary purposes and often discarded after the final positive prints were made. Because of the nitrates used in preparing the paper and the preferred thin paper itself, Van Dyke prints are often extremely brittle and susceptible to damage. Van Dyke prints should be stored separately and, when possible reformatted before the image degrades unacceptably.
, a coupling agent, and an acid stabilizer to produce a dark line on a white ground. The Diazo positive print was considered more readable than a negative blueprint, and the dry process eliminated the image distortion of wet paper.
As with other earlier reprographic processes, a translucent original drawing was placed over a sheet of the sensitized paper and exposed to light. However, the next step exposed the paper to an ammonia
gas. This alkaline gas catalyzed a reaction between the diazo salts and the coupling agent to produce an image that fixed in the paper over several days. Typically these prints have blue or dark purple lines on a mottled cream-colored background, although line and ground colors can vary.
A related process is the sepia Diazo print, which produced either a positive or negative print in dark brown and light tones. The negative versions of these prints were most often produced as intermediaries, like the earlier Van Dyke process, to allow corrections and revisions without disturbing the original drawing. In the negative printing process, additional resins and oils were sometimes added to the paper support to increase translucency. Positive sepia prints, generally made on opaque paper, were typically used as an alternative to positive blueline Diazo prints.
Both blueline and sepia prints were often poorly and cheaply processed, resulting in undesirable residual chemical content. Off-gassing of sulfurous compounds, image fading, and yellowing of the paper support are common signs of degradation and are not reversible. Diazo prints are also highly light-sensitive and can fade to illegibility within a short period of exposure to ultraviolet light.
In archival practice, Diazo prints are the most common reprographic format encountered in late 20th century architectural collections. However, their inherent fragility and fugitive images, as compared with blueprints and earlier processes, makes their care problematic. Diazos—particularly sepia prints, which readily transfer color to adjacent papers—should be physically segregated from all other types of media. Exposure to light and pollutants in air should be minimized, and wherever possible, original drawings or reformatted prints should be kept for reference.
Drawings should be grouped and identified for ease in retrieval, preferably within folders that are cut to fit the full dimensions of the corresponding container. As with rolled materials, the potentially damaging chemical interactions of print processes should be considered when grouping drawings in folders. Wherever possible, for example, blueprints should be segregated from diazotypes, and sepia diazo prints should be stored alone to the extent possible.
supports many architectural archivists in their professional responsibilities. In particular, the SAA's Architectural Records Roundtable is a primary forum for discussion of issues of acquisition, identification, description, conservation, and digital preservation of a wide variety of architectural documentation.
Reprography
Reprography is the reproduction of graphics through mechanical or electrical means, such as photography or xerography. Reprography is commonly used in catalogs and archives, as well as in the architectural, engineering, and construction industries....
of architectural drawing
Architectural drawing
An architectural drawing or architect's drawing is a technical drawing of a building that falls within the definition of architecture...
s, covers a variety of technologies, media, and supports typically used to make multiple copies of original technical drawing
Technical drawing
Technical drawing, also known as drafting or draughting, is the act and discipline of composing plans that visually communicate how something functions or has to be constructed.Drafting is the language of industry....
s and related records created by architects, landscape architect
Landscape architect
A landscape architect is a person involved in the planning, design and sometimes direction of a landscape, garden, or distinct space. The professional practice is known as landscape architecture....
s, engineers, surveyors
Surveying
See Also: Public Land Survey SystemSurveying or land surveying is the technique, profession, and science of accurately determining the terrestrial or three-dimensional position of points and the distances and angles between them...
, mapmakers
Cartography
Cartography is the study and practice of making maps. Combining science, aesthetics, and technique, cartography builds on the premise that reality can be modeled in ways that communicate spatial information effectively.The fundamental problems of traditional cartography are to:*Set the map's...
and other professionals in building and engineering trades.
Within the context of archival preservation, the custodians of architectural records must consider many aspects of identification and care when managing the artifactual nature of these materials. Storage containers, handling, paper and chemical compositions and interactions, ultraviolet light exposure, humidity, mold, and other agents of potential harm all interact to determine the longevity of these documents. As well, architectural reprographic drawings are often in very large formats, making storage and handling decisions especially complex.
History
With the rise of the professionalized practice of western architectureArchitecture
Architecture is both the process and product of planning, designing and construction. Architectural works, in the material form of buildings, are often perceived as cultural and political symbols and as works of art...
in the second half of the 19th century, the field of architectural reprography—and the corresponding developments of photography
Photography
Photography is the art, science and practice of creating durable images by recording light or other electromagnetic radiation, either electronically by means of an image sensor or chemically by means of a light-sensitive material such as photographic film...
and mass-produced wood-pulp paper
Paper
Paper is a thin material mainly used for writing upon, printing upon, drawing or for packaging. It is produced by pressing together moist fibers, typically cellulose pulp derived from wood, rags or grasses, and drying them into flexible sheets....
—saw significant experiments and advances in technology. Beginning with major refinements in blueprinting processes in the 1840s, through the widespread adoption of diazotype printing after World War II, the design profession turned to analog architectural reprography to create accurate, to-scale reproductions of original drawings created on tracing paper, vellum, and linen supports. These copies were typically used throughout the architect’s own design process and also for distribution to clients, contractors, governmental agencies, and other interested parties. However, the integration of CAD—or Computer-Aided Design
Computer-aided design
Computer-aided design , also known as computer-aided design and drafting , is the use of computer technology for the process of design and design-documentation. Computer Aided Drafting describes the process of drafting with a computer...
—over the last twenty-five years of design practice has made analog reprography far less common in the profession and more ephemeral in nature. For archivists, curators, librarians and other custodians of architectural records, traditional reprographic formats are now often seen as historic documents, with attendant needs for long-term care and conservation.
Major Analog Processes
Both the underlying support—paper or plastic—and the image type are used to identify the specific processes used in architectural reprography. Between the late 19th century and the late 20th century, several processes emerged as the preferred methods, used for decades, while other less common processes were employed for shorter periods of time.Blueprints
First developed in 1725, blueprinting uses a wet process to produce an image of white lines on a cyanCyan
Cyan from , transliterated: kýanos, meaning "dark blue substance") may be used as the name of any of a number of colors in the blue/green range of the spectrum. In reference to the visible spectrum cyan is used to refer to the color obtained by mixing equal amounts of green and blue light or the...
or Prussian blue
Prussian blue
Prussian blue is a dark blue pigment with the idealized formula Fe718. Another name for the color Prussian blue is Berlin blue or, in painting, Parisian blue. Turnbull's blue is the same substance but is made from different reagents....
ground. To make a blueprint, a heavy paper (or more rarely drafting linen
Drafting linen
From the late 19th century until the middle of the 20th century, drafting linen, also known as drafting cloth, was commonly used as an alternative to wood-pulp and rag papers in creating technical drawings. Its major benefits were considerable strength, especially in erasing and redrawing,...
) support is impregnated with potassium ferricyanide
Potassium ferricyanide
Potassium ferricyanide is the chemical compound with the formula K3[Fe6]. This bright red salt contains the octahedrally coordinated [Fe6]3− ion. It is soluble in water and its solution shows some green-yellow fluorescence.-Preparation:...
and ferric ammonium, placed under a translucent original drawing, weighted with glass, and exposed to ultraviolet light. After sufficient light exposure, the glass and original drawing are removed and the blueprint paper is washed to reveal a negative image. This same process, using an intermediary reprographic drawing, could also be used to produce a positive blueprint—blue lines on a white ground—however, this more expensive and time-intensive method was far less commonly employed.
The major disadvantages of the blueprint process, however, included paper distortions caused by the wet process which might render scale drawings less accurately, as well as the inability to make further copies from the blueprints. Nonetheless, for its efficiency and low cost, the blueprint process, further simplified and mechanized by the turn of the 20th century, became the most widely-used reprographic process between the mid-19th century and the latter half of the 20th-century.
In archival settings, because the process involves ammonium
Ammonium
The ammonium cation is a positively charged polyatomic cation with the chemical formula NH. It is formed by the protonation of ammonia...
, the resulting prints should not be stored in contact with other papers that have a buffered reserve, nor should blueprints be de-acidified, as the resulting chemical interactions can cause irreversible image loss. Blueprints are also highly light-sensitive and should not be exposed to ultraviolet light for long periods of time.
Pellet prints
Invented in 1887 by Henry Pellet, the Pellet process uses a wet process to produce an image of cyan or Prussian blue lines on a white ground. Essentially, this process produces a positive image, while a blueprint produces a negative one. To make a Pellet print, a paper (or more rarely drafting linen) support is coated with ferricFerric
Ferric refers to iron-containing materials or compounds. In chemistry the term is reserved for iron with an oxidation number of +3, also denoted iron or Fe3+. On the other hand, ferrous refers to iron with oxidation number of +2, denoted iron or Fe2+...
salts suspended in a gelatin emulsion, placed under a translucent original drawing, weighted with glass, and exposed to ultraviolet light. As with the blueprint process, after sufficient light exposure, the original drawing is removed, the paper washed in a ferrocyanide
Ferrocyanide
Ferrocyanide is the name of the anion Fe64−. In aqueous solutions, this coordination complex is relatively unreactive. It is usually available as the salt potassium ferrocyanide, which has the formula K4Fe6....
bath, and then rinsed in an acidic bath to reveal a positive image. This process required fewer steps than creating a positive blueprint, and was thus more widely employed during the late 19th and early 20th centuries.
In an archival setting, Pellet prints should be treated and stored under the same conditions as blueprints.
Van Dyke prints
The Van Dyke process, invented by F. R. Van Dyke in 1901, created an intermediary print—a white line on a dark brown ground—that could used in any of several other processes, such as blueprinting, to create a positive print, i.e. a dark line on a light ground. Using a translucent vellum support, the paper was prepared with a coating of silver salts. The vellum was then united with the original drawing, exposed to ultraviolet light, and later washed in a sodium thiosulfateSodium thiosulfate
Sodium thiosulfate , also spelled sodium thiosulphate, is a colorless crystalline compound that is more familiar as the pentahydrate, Na2S2O3•5H2O, an efflorescent, monoclinic crystalline substance also called sodium hyposulfite or “hypo.”...
bath.
In an archival setting, Van Dyke prints are relatively rare, as they were created for temporary purposes and often discarded after the final positive prints were made. Because of the nitrates used in preparing the paper and the preferred thin paper itself, Van Dyke prints are often extremely brittle and susceptible to damage. Van Dyke prints should be stored separately and, when possible reformatted before the image degrades unacceptably.
Diazotypes
By the middle of the 20th century, wet-process reprographic techniques such as blueprinting, Pellet, and Van Dyke printing were largely superseded by various dry-printing processes. The most common of these is the Diazotype process, refined in 1920s, which used paper supports sensitized with diazonium saltsDiazonium compound
Diazonium compounds or diazonium salts are a group of organic compounds sharing a common functional group R-N2+ X- where R can be any organic residue such alkyl or aryl and X is an inorganic or organic anion such as a halogen...
, a coupling agent, and an acid stabilizer to produce a dark line on a white ground. The Diazo positive print was considered more readable than a negative blueprint, and the dry process eliminated the image distortion of wet paper.
As with other earlier reprographic processes, a translucent original drawing was placed over a sheet of the sensitized paper and exposed to light. However, the next step exposed the paper to an ammonia
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...
gas. This alkaline gas catalyzed a reaction between the diazo salts and the coupling agent to produce an image that fixed in the paper over several days. Typically these prints have blue or dark purple lines on a mottled cream-colored background, although line and ground colors can vary.
A related process is the sepia Diazo print, which produced either a positive or negative print in dark brown and light tones. The negative versions of these prints were most often produced as intermediaries, like the earlier Van Dyke process, to allow corrections and revisions without disturbing the original drawing. In the negative printing process, additional resins and oils were sometimes added to the paper support to increase translucency. Positive sepia prints, generally made on opaque paper, were typically used as an alternative to positive blueline Diazo prints.
Both blueline and sepia prints were often poorly and cheaply processed, resulting in undesirable residual chemical content. Off-gassing of sulfurous compounds, image fading, and yellowing of the paper support are common signs of degradation and are not reversible. Diazo prints are also highly light-sensitive and can fade to illegibility within a short period of exposure to ultraviolet light.
In archival practice, Diazo prints are the most common reprographic format encountered in late 20th century architectural collections. However, their inherent fragility and fugitive images, as compared with blueprints and earlier processes, makes their care problematic. Diazos—particularly sepia prints, which readily transfer color to adjacent papers—should be physically segregated from all other types of media. Exposure to light and pollutants in air should be minimized, and wherever possible, original drawings or reformatted prints should be kept for reference.
Other Analog Processes
- Hectographic prints
- Ferrogallic prints
- Gel-lithographs
- Photostatic prints
- Wash-Off prints
- Silver halide prints
- Electrostatic prints
Cleaning, Flattening, and Repairing
For large collections of architectural materials, conservation work can address several areas of concern. Consultation with a professional conservator is recommended, although some minor treatments can be accomplished by general caretakers with training. Rolled and folded reprography, once cleaned, can be flattened through humidification. Cleaning may be done with white vinyl erasers, using great care in areas of friable media, such as graphite and colored pencil. Tears, losses, and other surface damage should be treated by a professional conservator. For particularly fragile or frequently-handled prints, sheets may be encapsulated in polyester or polypropylene film for additional support and protection. This is not recommended, however, for reprographic prints with annotations in friable media.Rolled Storage
The most common form of storage for architectural drawings—both for drawings in active professional use and in archival environments—has traditionally been in rolls. While this allows for efficiency in the use of space and ease of retrieval, potentially damaging situations can arise from a casual approach to roll storage. For reprographic drawings on paper supports, rolling can stress paper fibers and make unrolling for examination more difficult. Small rolls can be easily crushed and ends can be creased and torn without additional protective wrapping and support.Flat Storage
In circumstances where fragile, rigid, or otherwise atypical media makes rolled storage unfeasible, storage in flat boxes or flatfile drawers can be the best choice. Acid-free and lignin-free portfolio boxes, ideally no more than four inches deep, can be cost-effective and allow more flexibility in arrangement on shelving. Flatfile furniture should meet the minimum requirements of archivally-sound construction—powder- or enamel-coated steel units with no rust or sharp edges that could damage materials while stored or moved in and out of the drawers.Drawings should be grouped and identified for ease in retrieval, preferably within folders that are cut to fit the full dimensions of the corresponding container. As with rolled materials, the potentially damaging chemical interactions of print processes should be considered when grouping drawings in folders. Wherever possible, for example, blueprints should be segregated from diazotypes, and sepia diazo prints should be stored alone to the extent possible.
Reformatting
For most drawings, especially those that are oversized or significantly damaged, photographic reproduction remains the best method of accurately reproducing the fine details of a drawing. For drawings that are not significantly damaged or that are encapsulated in a polyester film, digital flat-bed scanning or other mechanical methods may be used.Professional Resources
The Society of American ArchivistsSociety of American Archivists
The Society of American Archivists is the oldest and largest archivist association in North America, serving the educational and informational needs of more than 5,000 individual and institutional members...
supports many architectural archivists in their professional responsibilities. In particular, the SAA's Architectural Records Roundtable is a primary forum for discussion of issues of acquisition, identification, description, conservation, and digital preservation of a wide variety of architectural documentation.
Further reading
- Dessauer, J. H. & Clark, H. E. (1965). Xerography and Related Processes. London and New York: Focal Press.
- Kissel, E. & Vigneau, E. (1999). Architectural Photoreproductions: a manual for identification and care. New Castle, Del.: Oak Knoll Press.
- Lowell, W. & Nelb, T. R. (2006). Architectural Records: managing design and construction records. Chicago: Society of American Archivists.
- Reed, J., Kissel, E., & Vigneau, E. (1995). Photo-Reproductive Processes Used for the Duplication of Architectural and Engineering Drawings: creating guidelines for identification. Book and Paper Group Annual, 14.
- Reprographic Guide: technical data and applications of most processes and services performed by reprographic firms. (1981). [Franklin Park, Ill.]: The Association.
- Tyrell, A. (1972). Basics of Reprography. London and New York: Focal Press.
- Verry, H. R. (1958). Document Copying and Reproduction Processes. London: Fountain Press.