Since diazo prints must be protected when not in use, framing them for display should be avoided. Diazo printing was one of the most economic methods of document reproduction of large engineering and architectural drawings for many years.Ī problem with diazo blueline prints was that with continued exposure to UV light, either natural sunlight or office fluorescent, a blueline would fade over a span of months if indoors, or days if outdoors. The range of colors for the lines that resulted were blue, black, or sepia. The original was peeled from the diazo paper and fed into the developing chamber where exposure to ammonia fumes caused additional chemical reaction resulting in the lines changing color from pale yellow to a visible dark color. Once this process was complete, the undeveloped image could often be seen as very light yellow or white marks/lines on the diazo sheet. The light penetrated through the original and neutralized the light sensitive diazonium salt in the area on the sheet that would become the white area on the copy. There were two chambers inside the machine: the first was the exposure area, where the sandwich of the master and diazo paper passed in front of a UV lamp.
The original document was laid on top of the chemically-coated side of a sheet of the diazo paper. Depending on the thickness of the master and the media type, the intensity of the UV & light exposure light would be adjusted.Ī traditional whiteline street map with intense blue background. Any media that allowed some light to pass through worked as a master. The process starts with original documents created on a translucent medium such as polyester film, vellum, and bond paper. Other comparable dye-based prints are known as blacklines. In the early 1940s, cyanotype blueprint began to be replaced by diazo & prints, also known as whiteprints, which have blue lines on a white background, and are often called & bluelines. While whiteprints are just the reverse - white overall with the drawing in blue. Avoid all buffered boards, dry mounting and laminating.Ī true blueprint has an overall blue color with the drawing in white (photo 1).
Since cyanotypes are light sensitive they require dark storage in neutral (7.0) pH materials making them unsuitable for framing display. Prints that have faded due to prolonged exposure to light can often be significantly restored to their original tone by simply temporarily storing them in a dark environment. Another unusual characteristic is its regenerative ability. The chemicals used in developing cyanotypes are sensitive to alkali environments and should not be matted and framed using chemically buffered materials which could accelerate their fading. It was a simple and economical way to duplicate large-scale copies for projects. So generally avoid heat, UV light and the solvents in spray adhesives.Ĭyanotypes, also called cyan-blue prints, are a photographic process popular for engineering diagrams well into the 20th century. They are colored by ferric ferrocynaide which is known to be fairly stable in light and air but additional UV protection is always desirable. Later processes used other photosensitive ferric compounds which evolved into the cyanotype, still producing a blue background and became known as blueprints.īlueprints are sensitive to the presence of alkalinity and the blue eventually turns brown when alkaline materials are used. The result was a copy of the original image-usually of a technical drawing, elevation or diagram-with the background tinted dark blue and the image as a whiteline reproduction. Paschke, CPF GCF "Blueprints Then and Now" August 2011Ī French chemist, Alphonse Louis Poitevin, discovered in 1861 that images could be reproduced from translucent documents by exposing ferro-gallate coated paper to UV light to develop a stable blue or black dye to emerge.
#BLUE PRINTS FRAMED ARCHIVE#
Chris Paschke - Blueprints Then and Now Paschke Online Designs Ink Publishing Article Archive and Reference Library Articles by Chris A.
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