# Were blueprints really blue? **URL:** \ **Category:** Factual Questions\ **Created:** [December 30, 2013, 4:57am UTC](https://boards.straightdope.com/t/were-blueprints-really-blue/677459 "2013-12-30T04:57:23Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Artemis\_Tardis](https://avatars.discourse-cdn.com/v4/letter/a/4bbf92/32.png) [@Artemis\_Tardis](https://boards.straightdope.com/u/Artemis_Tardis)\ **Post date:** [December 30, 2013, 4:57am UTC](https://boards.straightdope.com/t/were-blueprints-really-blue/677459/1 "2013-12-30T04:57:23Z")
We always see on old Tom & Jerry cartoons blueprints made with white ink on blue paper. Besides looking nice and neat, is there any specific reason for blueprints being… blue? I am pretty sure they got this name because of their distinctive colour, right? ---
**Author:** ![Joey\_P](https://avatars.discourse-cdn.com/v4/letter/j/919ad9/32.png) [@Joey\_P](https://boards.straightdope.com/u/Joey_P)\ **Post date:** [December 30, 2013, 4:58am UTC](https://boards.straightdope.com/t/were-blueprints-really-blue/677459/2 "2013-12-30T04:58:57Z")
Yes, they were really blue. I remember the classroom would stink like ammonia when someone was printing one. Why they were printed like that and not just on a big printer (plotter) I don’t know. I’m sure it’s just legacy\* at that point, I’m not sure if they still do it anymore. That is, they probably had a computer that only interacted with the blueprint machine. I know AutoCAD worked just fine with the plotter. ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [December 30, 2013, 5:03am UTC](https://boards.straightdope.com/t/were-blueprints-really-blue/677459/3 "2013-12-30T05:03:03Z")
> [@Joey\_P](#): > > Yes, they were really blue. I remember the classroom would stink like ammonia when someone was printing one. Why they were printed like that and not just on a big printer (plotter) I don’t know. I’m sure it’s just legacy at that point, I’m not sure if they still do it anymore. Because, they weren’t printed. They are photographic negatives made by contact printing from the originals. The originals were pen (or pencil) drawings on vellum. The original blueprint process was the first fast, inexpensive way to make multiple copies from the originals. ---
**Author:** ![chappachula](https://avatars.discourse-cdn.com/v4/letter/c/d2c977/32.png) [@chappachula](https://boards.straightdope.com/u/chappachula)\ **Post date:** [December 30, 2013, 5:05am UTC](https://boards.straightdope.com/t/were-blueprints-really-blue/677459/4 "2013-12-30T05:05:26Z")
Blueprints haven’t been blue for 60 years. They were replaced by “whiteprints” in the 1970’s, and then by xerox techniques and today, of course, by computerizd printers. [wiki](http://en.wikipedia.org/wiki/Blueprint) ---
**Author:** ![Capt\_Kirk](https://avatars.discourse-cdn.com/v4/letter/c/779978/32.png) [@Capt\_Kirk](https://boards.straightdope.com/u/Capt_Kirk)\ **Post date:** [December 30, 2013, 5:06am UTC](https://boards.straightdope.com/t/were-blueprints-really-blue/677459/5 "2013-12-30T05:06:24Z")
Relevant wiki [http://en.wikipedia.org/wiki/Blueprint](http://en.wikipedia.org/wiki/Blueprint) **Capt** Ninjaed ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [December 30, 2013, 5:08am UTC](https://boards.straightdope.com/t/were-blueprints-really-blue/677459/6 "2013-12-30T05:08:37Z")
They were blue because that was the color of the light-sensitive pigment that was used to make them. [Blueprints](http://en.wikipedia.org/wiki/Blueprint) were an early way to make multiple exact copies of drawings. ---
**Author:** ![Joey\_P](https://avatars.discourse-cdn.com/v4/letter/j/919ad9/32.png) [@Joey\_P](https://boards.straightdope.com/u/Joey_P)\ **Post date:** [December 30, 2013, 5:08am UTC](https://boards.straightdope.com/t/were-blueprints-really-blue/677459/7 "2013-12-30T05:08:59Z")
> [@beowulff](#): > > Because, they weren’t printed. > They are photographic negatives made by contact printing from the originals. > The originals were pen (or pencil) drawings on vellum. I either forgot or didn’t know that. Our class never had access to that machine, but the next class up got to use it if they made something really good. I just remember smelling it from time to time when we’d walk in and it was still running. > [@](#): > > The original blueprint process was the first fast, inexpensive way to make multiple copies from the originals. So why do that over a photocopier or mimeograph machine? Is it just that that industry had been using them for so long and that’s what they were used to? Those machines have been around since the '70’s/'80’s and are much faster. ---
**Author:** ![Old\_Eel](https://avatars.discourse-cdn.com/v4/letter/o/977dab/32.png) [@Old\_Eel](https://boards.straightdope.com/u/Old_Eel)\ **Post date:** [December 30, 2013, 5:18am UTC](https://boards.straightdope.com/t/were-blueprints-really-blue/677459/8 "2013-12-30T05:18:56Z")
Blue blueprints may have been phasing out in the 1970’s, but I still saw plenty of new blue ones in that time. ---
**Author:** ![running\_coach](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/running_coach/32/15836_2.png) [@running\_coach](https://boards.straightdope.com/u/running_coach)\ **Post date:** [December 30, 2013, 5:21am UTC](https://boards.straightdope.com/t/were-blueprints-really-blue/677459/9 "2013-12-30T05:21:28Z")
I worked in a blueprint shop for a short time in 1983 and it was blueprints all the way, no whiteprints. ---
**Author:** ![JWT\_Kottekoe](https://avatars.discourse-cdn.com/v4/letter/j/3ec8ea/32.png) [@JWT\_Kottekoe](https://boards.straightdope.com/u/JWT_Kottekoe)\ **Post date:** [December 30, 2013, 5:38am UTC](https://boards.straightdope.com/t/were-blueprints-really-blue/677459/10 "2013-12-30T05:38:04Z")
When I worked in construction and later in electronic design in the early 1970’s we used diazo prints (blue lines on white paper). They were still called “blueprints” by everyone I knew. In those days Xerox machines were already ubiquitous, but they were expensive and were limited, in my experience, to small formats like 8.5 by 11, wholly unsuited to large engineering or architectural drawings. The reproduction machines were compact and quite fast; there certainly was no digital plotter that could do anything approaching it in speed or quality. Remember, those were the days in which a typical computer printer that cost thousands of dollars, could print at ten characters per second. ---
**Author:** ![septimus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/septimus/32/410_2.png) [@septimus](https://boards.straightdope.com/u/septimus)\ **Post date:** [December 30, 2013, 5:50am UTC](https://boards.straightdope.com/t/were-blueprints-really-blue/677459/11 "2013-12-30T05:50:52Z")
Not only were blueprints blue in the 1970’s, but sepia prints were sepia-colored. Engineers often commented that their job was producing pieces of paper, and the minutiae of the reproduction processes were part of the job. My job was on the periphery, and the significance of “sepia” or “update the vellums” was often lost on me. Two vivid memories I have of the engineering paperwork I was involved with in the 1970’s are [ul] [li] I wrote my code and prepared documentation for circuitry _with ink_. However all official documents were done _with pencil_. (This seems opposite of what one might expect.)[/li][li] Among the documents we produced were very complex and detailed installation instructions, often with long lists of wiring coordinates. Failure to install correctly could be very expensive so these documents were important. At one point we started getting reports of installation failures of a system that was fully debugged and successful. Why? _It turned out the drafting department, idle and looking to keep busy, had unilaterally retyped (without proofreading) the installation instructions to give the margins “better balance.”_ :smack:[/li][/ul] ---
**Author:** ![cmyk](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cmyk/32/3353_2.png) [@cmyk](https://boards.straightdope.com/u/cmyk)\ **Post date:** [December 30, 2013, 5:55am UTC](https://boards.straightdope.com/t/were-blueprints-really-blue/677459/12 "2013-12-30T05:55:30Z")
They were so blue, they played the harmonica. ---
**Author:** ![usedtobe](https://avatars.discourse-cdn.com/v4/letter/u/ec9cab/32.png) [@usedtobe](https://boards.straightdope.com/u/usedtobe)\ **Post date:** [December 30, 2013, 6:18am UTC](https://boards.straightdope.com/t/were-blueprints-really-blue/677459/13 "2013-12-30T06:18:18Z")
Draftsman 1971-73. I have never sen a “blueprint”. The standard drawing size (I have a copy os a monster I drew on my wall) is 24x36 - much larger than any competing copy technique. Process: 1. Draw original on velum. 2. Get original signed-off 3. Take vellum to reeks-of-ammonia “blueprint” machine 4. Place velum (right side up) over ppaper 5. Feed velum-and-paper sandwich through machine. 6. Send print to shop; file velum The print produced was blue on white. There was also a material which was semi-transparent - it could be used to produce a (poor quality) print. It turns nearly completely opaque after 40 years (the thing on the wall). I’m guessing the difference is the cost of the materials - to produce a white-on-blue would seem to be (intuitively) more expensive (turning the entire thing blue vs a couple of square inches) than the “whiteprint”. We still called them “blueprints” This was mechanical - I have seen blue backgrounds only on architectural and maritime drawings. Trivia: the ability to produce a full-size drawing for pennies came in handy. We made steering gears and related bits for heavy trucks. Some of these were one-off’s. In the case of pitman arms, we had to get the drawing precise as to shape of the thing - it turned out the guys in the shop would pick up a chunk of iron 2" thick and 2’ long, and start pounding on it until the curves were such that they could lay the part on the drawing to check dimensions - they never measured the curve or the offset - they just used the drawing as a go-no-go guage. ---
**Author:** ![Terry\_Kennedy](https://avatars.discourse-cdn.com/v4/letter/t/c57346/32.png) [@Terry\_Kennedy](https://boards.straightdope.com/u/Terry_Kennedy)\ **Post date:** [December 30, 2013, 11:12am UTC](https://boards.straightdope.com/t/were-blueprints-really-blue/677459/14 "2013-12-30T11:12:27Z")
> [@Joey\_P](#): > > So why do that over a photocopier or mimeograph machine? Is it just that that industry had been using them for so long and that’s what they were used to? Those machines have been around since the '70’s/'80’s and are much faster. I have blueprints longer than 50 feet in my collection. The (low) technology needed to make a blueprint scales quite easily to large sizes. ---
**Author:** ![gotpasswords](https://avatars.discourse-cdn.com/v4/letter/g/c57346/32.png) [@gotpasswords](https://boards.straightdope.com/u/gotpasswords)\ **Post date:** [December 30, 2013, 1:03pm UTC](https://boards.straightdope.com/t/were-blueprints-really-blue/677459/15 "2013-12-30T13:03:08Z")
[QUOTE=usedtobe] I’m guessing the difference is the cost of the materials - to produce a white-on-blue would seem to be (intuitively) more expensive (turning the entire thing blue vs a couple of square inches) than the “whiteprint”. We still called them “blueprints” [/QUOTE] If you’re _printing_ blue ink, yes, printing acres of blue around white lines will be expensive, but this is a photographic sort of process where the ability to be blue or not is in the paper, edge to edge. Somewhere in the 70’s, diazo/whiteprint/blueline technology became cheaper, but the process was somewhat inferior to blueprints as the prints would fade with exposure to light, and the processing was noxious. About the only useful aspect to bluelines was the ability to mark up, correct or annotate drawings on white paper, rather than trying to see notes on blue. ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [December 30, 2013, 1:13pm UTC](https://boards.straightdope.com/t/were-blueprints-really-blue/677459/16 "2013-12-30T13:13:10Z")
In a science fiction novel (I think it was Keith Roberts’ _Pavane_), people in a Far-Future-Fallen-From-Technology have monks copying past knowledge, a la Medieval _scriptoria_, including blueprints, entirely by hand. When they figure out that blueprints were made that way because of the reproduction technology they’re ecstatic, because it means they no longer have to draw in all that wasteful blue by hand. ---
**Author:** ![chappachula](https://avatars.discourse-cdn.com/v4/letter/c/d2c977/32.png) [@chappachula](https://boards.straightdope.com/u/chappachula)\ **Post date:** [December 30, 2013, 1:25pm UTC](https://boards.straightdope.com/t/were-blueprints-really-blue/677459/17 "2013-12-30T13:25:14Z")
> [@CalMeacham](#): > > In a science fiction novel… the book is [A Canticle for Liebowitz](http://en.wikipedia.org/wiki/A_Canticle_for_Leibowitz) One of the finest books I’ve ever read…It is set in the far future, but it is really about our society, today. Oh. …it’s also about blueprints. 🙂 ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [December 30, 2013, 1:27pm UTC](https://boards.straightdope.com/t/were-blueprints-really-blue/677459/18 "2013-12-30T13:27:34Z")
> [@chappachula](#): > > the book is [A Canticle for Liebowitz](http://en.wikipedia.org/wiki/A_Canticle_for_Leibowitz) > > One of the finest books I’ve ever read…It is set in the far future, but it is really about our society, today. > Oh. …it’s also about blueprints. 🙂 Bingo. I had a hard time squaring it with Pavane, but Leibowitz makes more sense. ---
**Author:** ![Si\_Amigo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/si_amigo/32/2877_2.png) [@Si\_Amigo](https://boards.straightdope.com/u/Si_Amigo)\ **Post date:** [December 30, 2013, 1:33pm UTC](https://boards.straightdope.com/t/were-blueprints-really-blue/677459/19 "2013-12-30T13:33:23Z")
We ran blueprints for engineering release and blackprints (black background with white lines) of the same documents for manfacturing at an aerospace firm i worked at in the late 80s. Some sort of government contract requirement. After that most places started using big pen plotters and large scale xerox machines that made white background with black line prints. Now many places don’t bother to print out anything larger than 11x14th prints on a regular basis since drawings are now sent and viewed electronically to suppliers and customers. The only people I see plotting large scale drawings are the actual CAD guy doing the work and business guys using the plotters for charts. But I suspect that large construction firms (also aerospace and shipbuilders) print out full sized drawings. ---
**Author:** ![Musicat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/musicat/32/20189_2.png) [@Musicat](https://boards.straightdope.com/u/Musicat)\ **Post date:** [December 30, 2013, 1:48pm UTC](https://boards.straightdope.com/t/were-blueprints-really-blue/677459/20 "2013-12-30T13:48:49Z")
The blueprint process (also called Diazo or [Ozalid,](https://en.wikipedia.org/wiki/Ozalid_process) after the manufacturer that made some machines) was very simple and had the advantage of nearly unlimited length and very wide width. The original, on translucent or transparent medium, was mated to the copy material, that is, the original was placed on top of the copy material, which was light-sensitive, but not very; you could use it at room lighting for a few minutes without being exposed. The mated paper was fed into a continuous belt system, exposed to a high-intensity light, then the two parts were separated. The original was returned to the operator, and the copy was sent to an intense, heated ammonia bath for developing. The final product omitted the fixing step used for most photographic processes, which meant that the copy would fade over time, but since this was never intended to be a long-term copy, that wasn’t too important. I found that if you put a print in an envelope and kept it away from heat, light and air, it stayed fresh-looking for years. The deterioration was, at least for black on white prints, mostly that the substrate turned brown and looked aged, but didn’t render the image unusable. I saw one gnormous machine once that was so wide that two operators could stand in front, each feeding the belts with separate jobs. It took about 30-45 seconds from start to finish for one copy, but you could keep feeding as long as the belt was clear. Later machines used fluorescent lights instead of hi-intensity, which made the process much slower. These were the whiteprinters, and they also used ammonia vapor at a much lower concentration and didn’t heat it. This lessened the smell, and made cheaper machines that didn’t need as elaborate exhaust system. The process allowed for many kinds of coated paper for the copies. Although the architects used a blue, negative process, other industries used a black, positive process. Short-run music was commonly reproduced this way until the computer took over ca. 1990’s. Another kind of copy medium was itself translucent, and the copy could be used to make more copies, or stripped into an original to save hand copying time. This was usually sepia-toned, but I don’t know why. My guess why blueprints were blue, since they could have been black on white, is that that coating was the cheapest, or perhaps the first to be invented. I didn’t think musicians would go for white music on blue background, so I never priced that media or tried it. [Next page](https://boards.straightdope.com/t/were-blueprints-really-blue/677459.md?page=2)