Were blueprints really blue?

Factual Questions
21

Try making a copy of a 11" x 14" music score on your average Xerox machine, using heavy paper for the copy. Or even a common music part size at the time, 9.5" x 13". Easy on a Diazo machine, impossible on most Xerox ones. We could make a 4-page music part, 13" x 38", on heavy paper, in one piece (and fold it afterwards).

Another advantage the process had for musicians – we used pre-printed vellum music staff paper with the staff lines printed on the reverse side. If we had to erase something (all work was done in ink so the image would be opaque and sharp), the staff lines would not get erased. This saved time and made the result look better.

22

Some terms never die. The local print shop here* is called San Jose Blue, and of course almost everyone calls it San Jose Blueprint by mistake.

*They were around before Kinkos (now FedEx Office) and I’m amazed they are still able to compete.

23

The blueprints were blue because that was the color of the photographic emulsion after being exposed to light. The emulsion is a cyanide compound*. Back in college we used to mix up small batches of it by hand and apply it to all sorts of paper or cloth to make it photosensitive. The emulsion formula dates back to the 19th Century so it was a very early process. One advantage is that you don’t need a darkroom. It’s most sensitive to ultraviolet (we used to use ordinary sunlight, among other light sources, to make images) so you can handle/develop it in ordinary room light without screwing up the image.

Of course, if you screw up making the emulsion you can wind up with highly toxic stuff, but if you can make a batch of brownies you can do this successfully without hurting yourself. You just have to observe some elementary precautions and pay attention to what you’re doing.

  • Admittedly, that statement is somewhat simplified but I didn’t want to diverge into exacting detail and chemistry. If folks want the details they can look them up on their own.
24

I’ve been working with bridge plans for 35 years and I’ve only encountered real blue prints once- those for an old bascule bridge that we did rehab plans for. We don’t even make physical plans anymore, it’s all computer drafting. Prior to that, plastic film (mylar) was the norm for the originals. Earlier it was sepia, vellum, and linen.

25

I was a draftsman in Chicago in the late 70s. We had honest-to-goodness blue blueprints then.

26

Well, duh. That wasn’t the color of all photo emulsion. Did you read my posts describing other chemical formulas that resulted in image reversal, giving black on white instead of white on blue?

The question here is, why didn’t architects/draftsmen use the black on white formula? Cost? Not invented yet?

27

It’s always a joy to see cmyk post on any thread that has to do with color printing. :slight_smile:

28

Back around 1980 I worked in retail advertising. We used “blue lines” for layouts of full and half-page newspaper ads. We did smaller layouts on the copier. Even if there had been photocopiers that could handle a newspaper-sized sheet of paper, they would have been hideously expensive.

29

Pretty sure they’re called “blacklines” now. You can get full or half-size prints to work from, of course, since it’s all CAD.

30

Well, initially it probably was a matter of “not invented yet”. The type of blueprinting I did was with the ammonium iron(III) citrate and potassium ferricyanide system, which was, if I recall, developed around 1840 or so, so it pre-dated silver-based emulsion photography by a couple decades. The end result is an image in insoluble Prussian blue dye. You “develop” and “fix” the image by washing it in water. Although there are a few chemicals you can add to tweak the final result they are not essential to the process.

It really is a very simple system to use once you have the chemicals. I can see where it would have taken a long time to surpass its ease of use and low cost. There are a couple of other UV sensitive emulsions out there, but the only other one I’m at all familiar with required three chemicals for the emulsion, more chemicals for developing and fixing, and seemed a bit fussier overall, all of which would have made it costlier and probably accounts for why there are fewer examples of such prints.

The end result is also non-toxic (Prussian blue is even used therapeutically in medicine) which was a nice thing compared to some of the other byproducts produced by alternative 19th Century (and 20th Century) photography and photoreproductive systems.

It also allows fairly simple, same-scale endless reproduction of a drawing without need of printing press, optical equipment, or a lot of other paraphernalia. Wikipedia claims a blueprint in the late 1800’s was 1/10 the cost of redrawing a copy by hand. So, yeah, I think cost had a lot to do with it. I also think at some point inertia took over - firms needing engineering or architectural drawings were already set up for blueprinting so why invest in the equipment for a new process? Unless, of course, your blueprinting equipment was worn out but it was so low-tech that would definitely take awhile.

31

Just as an aside, I played a small role in putting the final nail in the coffin of blue lines (blueprints were already dead and buried). In the early '90s I was a member of a team at a very small company that made plotting software and hardware. Our system was so fast that we could print originals as fast as the competition could print duplicates. That made it possible to create collated sets of prints quicker and more easily then the old method - printing stacks of duplicates and then hand-collating them. Our system quickly became a must-have for blueprint shops. If they didn’t have it, and their competition did, they would get driven out of business.

Of course, technology marches on, and within 10 years everyone could do it (processing speed had increased so much that even crappy software could keep up). But, the company printed money during that decade…

32

I understand that the blueprint process was used ca. 1940-1960 (maybe earlier) in warehouses where duplicates of invoices, shipping notices, etc. were needed. As long as the original was on translucent or transparent stock, a copy could be made fairly easily and cheaply. In a warehouse, the ammonia smell wouldn’t be as much of a drawback as an office.

The Ozalid machine I bought in 1972, used, for $100, had a manual which touted the method of duplicating invoices, so I assume that was a typical application years earlier. By 1972, Xerography had eclipsed Diazo for all except large-document purposes. The machine weighted 450 lbs, drew 20 amps, needed a 6" exhaust duct and took an hour to warm up.

And think of the competition – until the first small-office Xerox 914, introduced about 1960 (one copy every 26 seconds!), there were very few practical ways to make a copy if you didn’t plan ahead and use carbon paper, like the 2-step Thermofax. Diazo was one of the best at the time.

33

Imho Liebowitz used blueprints as a plot device and the book would have been more or less the same had it instead used TPS reports with the new cover sheets. The real theme of the book is

Humanity is unable to learn from its past and is trapped in an endless cycle of war, collapse, regrowth, and renewed war.

34

WHAT?
You mean to tell me that the real theme of the book isn’t “blueprints” ? I never knew!!! I thought it was all just about the blueprints.
The book tells the story of 8000 years of human experience—and we all know that the most important human experience of all is the blueprint, right?
Actually, in addition to the heavy themes you mention ( war, learning from the past, etc)…one of my favorite aspects of the book is the way it documents the foibles of human pride. For example: the one-upmanship of the leader of the monastary. He cares less about the sacred relics of Lieibowitz,and more about getting the church bureacracy to grant official recognition of his sainthood, just because he wants his order of monks to out-do the rival order of monks from a nearby monastary.
[sorry for the hijack. But surely we all agree that every mention of the technology of blueprints should include a discussion of theology. Where else but the Dope! :slight_smile: ]
(And , yeah, the blueprints are a great plot device, too.)

35

What can I say, color is my raison d’être.

36

Lovely plummage!

37

(Sorry if this is redundant)

‘Blueprints’ are blue on white paper, not white on blue paper. The paper starts out white and turns blue everywhere except where the lines are.

HOWEVER, the Mythbusters are often shown drawing with white ink on blue paper.

At least I think so…

38

You’re right. The usual time-lapse footage of the blueprint is drawn on a blue background with an opaque white marker. Or is it silver? So yeah, it’s not accurate to how a legit blueprint is made, just a skeuomorphism of colors chosen to evoke the metaphor.

Anyhow, of course, blueprints are a photonegative effect of UV light activating the dye wherever the draftsman’s ink isn’t.

So, the white parts are the unexposed parts, as the ink occluded the sun’s light (or UV lamp).

Why, THANK YOU! licks featherspurrrrrrr***

39

That’s correct, but the end result is a negative image from the original, which is black pencil or pen on white, translucent background. To all appearances, it is a white image on blue background; the significant data is in the white portion of the drawing.

40

Well, the “blueprint” process was superseded by the “whiteprint” or “blue-line” process sometime in the 1970s, since xerographic copiers weren’t big enough until around 2000, and they were very expensive until sometime in the 80s or 90s.

I’m fairly familiar with the blue-line process, since I was an intern at a civil engineering company for 3 summers in college and did uncountable numbers of them.

First, you get the original mylar plot- this is generally plotted straight out of the drawing program (in our case, Microstation), and is a relatively thick translucent plastic sheet with black ink on it.

Then you took out a sheet of blue-line paper, which at the time was bright-yellow on one side. You put the mylar sheet above the yellow part right-side up.

Then you feed the sandwich of sheets into the blue-line machine on the lower rollers. This squeezes them together to hold them in place and shines a bright light of some sort through the mylar.

When the pages come out, the mylar is unchanged, but the blue-line paper is now white, except where the ink masked the yellow.

Now you feed it through the upper rollers where it is exposed to ammonia fumes, which chemically transform the yellow stuff into a more permanent blue.

That’s it. Sepias are done the same way, except that generally they were on vellum and intended more as temporary masters- we’d do things like make sepias to send to construction companies so they could print a couple dozen sets of plans for their crews. We’d send sets of bluelines to the land planners, developers and project managers earlier in the process, and once everything was finalized and signed, sepias (1st summer), or mylars (2nd and 3rd summers; got a plotter that cost less per sheet) We really didn’t do many sepias at all to be honest.

Nowadays, plotters, large-scale printers and large copiers aren’t cost prohibitive anymore, so I doubt they really even fool with bluelines at all.