Blue prints

Discussion in 'Alternative Processes' started by Uncle Goose, Apr 10, 2013.

  1. Uncle Goose

    Uncle Goose Member

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    Ok, I suppose blueprints are exactly the same as cyanotypes right? So I wonder, how did they make those blueprints? I suppose they used some sort of machine for this? I've looked at some old blueprints and the coating seems to be incredible evenly over the whole sheet (and it was a large sheet). So how did they coat the paper? I suppose dip and dunk or something like that? Just wondering.
     
  2. tkamiya

    tkamiya Member

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    There was a machine with rollers and chemicals. Take out a large sheet of paper (in daylight), put the original transparent sheet on top, feed it into the first roller.... then when it comes out, feed just the exposed paper back into another slot and it comes out of a third slot sort of damp. Let it dry for a while and it's ready.

    It was a predecessor for xerox copy machines. It was handy because it can handle huge size.
     
  3. Uncle Goose

    Uncle Goose Member

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    That I suspected already but I would like to know what machines they used to actually coat the paper, anybody has photographs of such installations?
     
  4. BrianShaw

    BrianShaw Member

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    This may help, even though it doesn't really answer your question. http://www.engineersupply.com/How-To-Make-Blueprints.aspx

    The coated paper appears to have "come from a factory in sealed container". The manufacturing details for the sensitized paper, which I think you are most interested in, remain a mystery.
     
  5. DWThomas

    DWThomas Subscriber

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    Yes, in the machines I saw/used back in the 1960s, the paper was already coated and came in standard cut sizes and rolls. I seem to recall nasty ammonia fumes from the development process.

    Obviously somebody coated the stuff, but as a dedicated production process.
     
  6. Born2Late

    Born2Late Subscriber

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    True blue prints produced a negative image of the original with white lines on a blue background.

    Blue line prints replaced classic blue prints probably 45 or more years ago. Blue line prints produce a positive image - blue lines with a white backgroung. The blue line prints utilize the diazo process. The paper is purchased precoated. While it is light sensitve, it rquires a very intense light source. As stated earlier, it uses ammonia as the developing agent. There is no fixing required and image is not very permanent.
     
  7. BrianShaw

    BrianShaw Member

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    I lived in the mimeograph era, but was too young to have anything to do with blueprints (other than seeing some under my Dad's arm when he was going/coming to/from work. I remember, though, always inhaling deeply the fumes on the mimeograph paper. Was that the same (ammonia), or was that aclohol? I just remember the "huffing" and not the identity of the fumes.
     
  8. tkamiya

    tkamiya Member

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    The paper came already coated as already said. The package looked like a giant version of a ream of today's Xerox paper, except one side of paper was faintly yellow or blue.

    I *think* it's ultra-violet sensitive. I don't recall paying any particular attention to light sensitivity while handling it but I also recall putting some objects on it and leaving it out under direct sun for few minutes to get images of the objects burned in.

    It was at least 35 years ago.
     
  9. bascom49

    bascom49 Subscriber

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    The Blue Print is Alive and Well

    As a land surveyor I make blue prints every day to reproduce copies of my final plats.

    We do use AutoCad for drafting and plot on a large format HP inkjet printer onto mylar.

    After I sign and seal the original we make blue line copies for our clients.

    It's an incredibly cheap and productive process.
     
  10. Prof_Pixel

    Prof_Pixel Member

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    I remember running a diazo engineering drawing copy machine in an engineering office the summer before my senior year in high school. That would be about 57 years ago. The worse part of the job was pouring the ammonia solution into the machine once or twice a day. I believe later machines took the ammonia out of a container with no pouring.
     
  11. falotico

    falotico Subscriber

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    Classic blue prints are indeed cyanotypes. They depend on iron ions gaining an electron from the action of light: Fe3+ + e- ==hv==> Fe2+

    Fe3+ ions will not form a complex with the ferriccyanide chemical; Fe2+ ions WILL form a complex with the ferriccyanide and form a blue compound which is often called Prussian Blue. A paper was dipped in the yellow, acqueous, ferric chloride solution and then allowed to dry in the dark. This coated the paper with Fe3+ ions. Next a line drawing of a building plan, machine part, etc. was placed over the coated paper and this assembly was put into bright sunlight, or somehow exposed to ultraviolet rays. Light going through the upper drawing would strike the Fe3+ ions and these would obtain an electron from the organic material which makes up the copy paper. The electron would enter the orbital of the Fe 3+ ion converting it to Fe2+, which is slightly brown in color. Since the oxidation number of the ions is reduced from 3+ to 2+, we say the Fe 3+ ion is reduced to Fe 2+. (Silver ions are also reduced by the action of light).

    Fe 3+ ions are soluble in water so they can be washed out, leaving the Fe 2+ behind. These Fe 2+ ions will complex to form Prussian Blue when the copy paper is washed with a ferriccyanide solution. Since the dark lines of the drawing prevent any light from striking the Fe 3+ ions, these line areas will remain light in color, producing a negative image. This is an inexpensive method of producing exact copies of drawings on paper, but requires liquid development.

    When diazo compounds were invented it was discovered that they would turn color in strong bases. Thus if you coated a paper with a particular diazo compound and exposed it to the fumes of ammonia the paper would turn blue. Ultraviolet light prevented this reaction from happening, so exposure under a drawing and development with ammonia fumes would produce a positive.

    Mimeograph depended on a paper master laid over a gel containing an aniline dye, usually blue, which was soluble in methyl alcohol. You typed on the master and the force of the typewriter letter striking the master would press the shape of the letter into the gel. An image of the letter would stick to the back of the paper master from this mechanical force, (this worked also with line drawings made with a pencil or ballpoint pen). This blue image was actually a relatively thick layer of gel containing blue dye.

    To make mimeograph copies the paper master was attached to a roller about eight inches in diameter which was rotated by a crank or motor. At each revolution a blank sheet of paper was fed into a slot where a wet sponge coated the blank with a thin layer of methyl alcohol. Since the dye was only soluble in methyl alcohol (not water) as the blank paper was pressed next to the blue dye gel image, the blue dye would dissolve and transfer to the blank paper. This made a fairly good copy that smelled of alcohol for about ten minutes. Xerox wiped out the market for this process.

    To be accurate, this process was not officially the "Mimeograph" process, IIRC, but was called by that name through common usage.
     
  12. sepiareverb

    sepiareverb Subscriber

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    Thank you for that falotico!
     
  13. Jim Noel

    Jim Noel Member

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    Yes, blueprint paper came coated. it was developed by passing through ammonia fumes,and came out essentially dry.