Authentic Blue Blueprints


At one point in history, blueprints were actually blue. Now, if you even see a dead tree version of plans or assemblages, they’re probably printed off with a plotter or large format printer. You can, however, make your own blueprints at home, as [Tyler] shows us in his Hackaday Project.

Back in the olden days, master drawings were traced onto large sheets of transparent film. These master prints were then laid over paper prepared with Potassium Ferricyanide and Ferric Ammonium Citrate to create an insoluble Prussian Blue background for the prints. Developing is easy – just expose the transparent positive and undeveloped paper to UV light, in the form of fluorescent bulbs or the sun.

[Tyler] began his blueprint creation process by getting a few design sketches of the RSI Aurora and Nautilus, editing them on a computer, and printing them out on transparency sheets. A solution of equal parts Potassium Ferricyanide and Ferric Ammonium Citrate were painted onto a piece of paper and allowed to dry. Exposing was a simple matter of laying the transparency over the undeveloped paper and setting it out in the sun for 20 minutes or so. After that, it’s a simple matter of washing off the unexposed chemicals and letting the newly created blueprint dry.

It’s a simple technique, but also very, very cool. Not exactly practical, given a plotter can spit out an architectural or assembly drawing of any building, vehicle, or device in a few minutes, but just the ticket for art pieces or extremely odd engineers.

Thanks [Sarah] for sending this in.

31 thoughts on “Authentic Blue Blueprints

  1. I’m old enough to remember making blueprints in my drafting class in high school, and the prints did not have a blue background with light lines. Real blueprints have a very light blue background and dark blue images. While the prints described here are very cool and make great art, they aren’t like real blueprints.

    1. Took a little work, but here:

      “blueprint, type of print used for copying engineering drawings and similar material. The name is popularly applied to two separate methods, more exactly designated as the blueprint and the whiteprint, or diazotype. In blueprinting, the older method, the drawing to be copied, made on translucent tracing cloth or paper, is placed in contact with paper sensitized with a mixture of ferric ammonium citrate and potassium ferricyanide, which is then exposed to light. In the areas of the sensitized paper not obscured by the lines of the drawing, the light reduces the ferric salt to the ferrous state, in which it reacts with the potassium ferricyanide to form insoluble prussian blue. The exposed paper is then washed in water, producing a negative in which the lines of the drawing appear in white against a dark blue background.

      In the whiteprinting method, the paper is sensitized with a mixture of a diazonium salt, a coupler that reacts with the diazonium salt to form an azo dye, and an acid that prevents coupling. Exposure to light destroys the diazonium salt. Final treatment with an alkaline agent, such as ammonia gas, neutralizes the acid, thereby bringing about the coupling reaction. Because it produces dark lines on a “white” or light background, whiteprinting has become the favoured method.”

      So the process you’re talking about is whiteprinting, while the process he’s using produces original blueprints.

  2. When I first started doing schematics, we had “blueprint” machines. The original drawings were done on translucent vellum (with pencils and stick-on symbols), then these were laid on top of coated paper and run through a machine (plenty of ammonia involved). The paper came out with blue lines and white background — the “negative” of a blueprint. I never saw any white-on blue drawings.

    1. Back in the states, I have a complete set of drawings: Original, vellum, and blue-print (while lines, blue background). These appear to have been part of an Engineering course in the 1940’s. The vellum was marked with pencil, then painstakingly perfectly inked. (no runs, all line-widths matched, even on curves and radii).

      Someday I’ll have to get them scanned. ;)

    2. Yeah – my dad used to bring home packets of the stuff because the engineers didn’t want to use anything that was ‘out of date’. I would take it, put whatever I could find on it to mask part of the coating, and give it about a minute of full sun exposure. Developing the paper was easy – I just needed to find a big container and a small bottle of household ammonia. One year, I used it as wrapping paper for Christmas. That was in the early 80’s and I would have been around 10 years old…

  3. I remember very well the ammonia-based blueline machines — my father was an architect and had one of those machines in his office in our basement in the 70s and early 80s. He’d pay my brother and I a few cents per sheet when he needed a large number of copies made. I used his drafting tools to make 3’x4′ hex paper (lots of patience) for role playing and wargaming. The ammonia process had awful odors. The bright side is that the ammonia bottles were — when depleted — still about 21% ammonia, or 7X stronger than cleaning solutions, meaning we always had ammonia for window cleaning.

  4. I remember those as well. Was in drafting class in high school at the time of the end of pencil/paper drafting and the start of CAD. The worst of it had to be the lettering tests.

    I had a friend that was giving away a blue line machine a few years back, wish I would have had the space for it….

  5. It would be neat if there was white ink for a plotter, or if you could load it with something similar, maybe like white out, to do the same but faster. That would be awesome.

    1. When I used to work at a reprographics shop (1992-1996) we used to make our own silhouettes for the range with Diazo paper. Roll up, take to side of building (in direct sun) unroll against wall, stand against, wait a few mins (untill most of the paper was white) roll back up and run through the developer machine. Oh and you haven’t gotten a paper cut until a commercial diazo developer pulls a 48″ paper edge along your hand at 6′ per sec.

    1. That guy needs to smack you a few more times until you actually explain what’s going on in the vid/pic ;)
      (Not that I have a laser to try this with, yet, but still…)

  6. Fond memories of spending a day at work with my dad when I was 8 or 9 or so. One of the things he taught me was how to run blueprints through the machine (possibly a Diazit, though I have no way to say for sure). I suspect this was as much because it was a chance for him not to have to smell the ammonia and that it kept me from running the electric eraser randomly (loved that thing!), but I thoroughly enjoyed it. That day was one of the experiences that showed me the wonder of the mechanical/electrical trades. So glad to see a piece on blueprinting here on HAD. Made my day!

  7. Hmmm. I have no desire to relive making blueprints or bluelines. I suppose if I was feeling nostalgic, I could get a leaky bottle of ammonia.
    But, I’m glad to see there are others that remember doing this.

  8. This is one of those articles that I use my evaluation formula: interest level * reproducibility (both out of 10), In this case due to the fact that the chemicals involved are not readily available it comes out at 10*.01 = .1 – not good.

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