I get that blueprints used to be that way due to various complicated lithographic processes. They are also still blue in TV and movies, probably because it’s a cliché and people expect them to be blue.
But is there any reason that they still need to be blue? I was walking past a jobsite a few days ago and near enough to some official looking people who were studying a large blue sheet that was partially rolled-up… my guess is this was a blueprint. Surely in today’s world of inexpensive printers and plotters we can crank out as many copies of a blueprint as we need, but as a regular black or blue line drawing on white paper.
Is there any practical reason why the print of a construction or job has to be a negative of the original? Does it help readability in bright sunlight?
Traditional blueprints died many years (maybe decades) ago. They were replaced by bluelines, which are positives (unlike blueprints which are negatives). Those have pretty much died also, replaced by large-format laser printers and inkjets.
ETA: I used to be an engineer at a small firm which made the world’s faster laser plotter controller. We could print collated sets of D-sized prints at one print every 3 seconds. This was so fast, it eliminated the need to copy sets - everyone could just get an original.
My dad owned a small roofing business for over a decade (just closed up this year), and many of the blueprints he would get were in fact blue. Now, whether or not they were technically “blueprints” I’m not sure.
They LOOKED like stereotypical blueprints though, where the lines weren’t perfect (looked copied), looked kind of grainy overall, etc.
This was not always the case though. If I remember correctly, most were on white paper with black ink. Only some of them looked like old fashioned blue prints.
I didn’t even know why blueprints are called that in English until I read “A canticle to Leibowitz”, and I started studying draftsmanship in the late 70s. Every “blueprint” I’ve seen in a Spanish museum was drawn, not litographed, so it was black-on-white like the ones I’m used to; I’ve never seen one in a movie; the plans for my grandparents’ flat (house built in the late 19th century) are black-on-white, both the oldest copies they have and the version drawn in the 1950s. The process used here to make multiple copies involved carbon paper, which also provided black-on-white drawings, although the bottom copy would be somewhat smudged. Some day I want to drop by the nearest College of Architecture and ask whether “blue” prints were ever in use here.
Then again, and it may be more apropos than it seems, American comic book artists traditionally used blue pencils to draw base lines with and then inked on that (the blue pencil didn’t copy), whereas Spanish ones have never bothered with such a thing: most don’t even draw any kind of base lines unless it’s for a very large drawing, and then they do it very softly in black pencil. The boxes labeled “traditional drawing techniques” seem to be completely different.
Old “blueprint” copies were made with an original that was a pen or pencil drawing on a translucent medium, such as vellum. The original was placed with a treated, light-sensitive paper in a glass frame, and exposed to sunlight. Because it was a contact print, the linework scaled almost perfectly, making it a VERY accurate print. Obviously, this method took a LONG time to create a bunch of copies, and because the paper WAS light-sensitive, it didn’t last very long in daylight.
Blue LINE prints were cheap and plentiful. The light-sensitive paper plus original are rolled through a device where the paper is exposed to a special light and ammonia fumes, producing a print. It is laborious, sinus-cleansing, and not quite as precise as the blueprint process. This print will also fade, although not as quickly as the old blueprint.
As photocopying got cheaper, huge print machines were created that could scan an original (which didn’t have to be translucent) and pop out as many prints as necessary. Those prints are distorted a bit, but the sacrifice is acceptable in order to yield the volume. These are often called “black line.”
Blue print paper and blue line paper become very FRAGILE with age, and if you were lucky enough to get a paper cut with the treated, unprocessed paper, you were in for a painful, slow-healing adventure!
~VOW
The enginering department where I used to work had a fireproof vault flled with old drawings going back 50 years.
Since about late 1990’s, they had a giant Xerox copier that would accept up to 3-foot wide originals, scan them (through a roller, not flatbed) and spit out a copy onto a roll of plain paper in black and white. It also did printouts directly from computer CAD drawings. Inkjet plotter could do colour from computers if needed, but was much more expensive. Scanning accounts for the hand-drawn look. Their CAD even allowed scanning and then areas could be blanked or overdrawn by computer.
None of the drawings even from 1960 appear to be blue, but I think that’s because they were originals. Even stuff from about 1970 appears to be a black-and-white copy with paper pasted over to redraw a section when a modification to the original building was needed. So blueprints were probably already on the way out by then.
Of course you have to be a multimillion dollar enterprise or producing a LOT of drawings to afford that sort of equipment way back when. However, evn in the early 70’s there was the Activator-stabilizer process for producing black and white photos in large format, my local library had that for aking prints of newspaper from microfilm.
I entered the engineering field in the early 70s, and bluelines were the method of reproducing prints from maps. Blue PRINTS were still available, often as record copies from years prior.
Black lines (photocopies) began late 80s, early 90s, I believe. The chief factor was COST.
Camera work was the gold standard for making quality reproducibles on mylar. The cameras were HUGE, and the negatives had enough silver in them that we recycled them for silver recovery.
Occasionally, you can find ANCIENT photocopies that were done on silver PAPER. Those babies are EXTREMELY light sensitive, and would barely be readable today, unless they were stored in absolute DARK.
~VOW