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Architecture Plan Copying: Why Blueprints Aren't Blue Now

Updated on April 12, 2012

Why you should read Part One of my History of Reprographics first

In Part One I hope I proved that reprographics is pretty interesting. That article was about how reprographics has progressed from hand-copying architect drawings to printing from AutoCAD. I also got into the types of paper architects have used as originals so they could be copied. My information came from an interview with Ewan Tallentire of Albion Repro & Graphics, a Denver-area reprographics shop. Now let me tell you about the copies, and why the things now called "blueprints" are black-and-white.

I should note that as I looked up details online, I found listings on the Internet for many of the things I said were obsolete. There are several things going on:

  • I could be misinformed (let me know if so)
  • Whatever-it-is does exist, but outside the US (Canada seems to still be using diazo machines)
  • Whatever-it-is is actually not available, but it's so recent the website hasn't been updated (you'd find out by calling the company)
  • The business behind the website went out of business recently (you'd find out by calling the company and not getting an answer)
  • Whatever-it-is is out there for a different purpose (pen plotters and vellum for artists, diazo for artists and silk-screeners, etc.)

Look, a blue blueprint!

This is a real blueprint, from 1932, of the tennis house of a Denver mansion.
This is a real blueprint, from 1932, of the tennis house of a Denver mansion.

Architectural copies: real blueprints

Real blueprints are actually blue (varying from a purplish color to a very deep blue), with whitish lines and letters. The original blueprints were made by a wet process called cyanotype, but later a “dry” process, called the diazo process, was developed. Real blueprints haven't been the standard for some time now; Ewan says he's never actually made blueprints himself, but colleagues of his remembered doing it.

The diazo process uses paper with a yellow coating of ferro-gallate, which comes in light-opaque packaging and has a limited shelf life. You put the original over one of the sheets and expose it to light, then expose the copy (now yellow with white lines) to ammonia vapor. In the early days, this meant putting the original over the yellow sheet in the sunlight for several minutes, then separating them and putting the copy in a cylinder, pouring some ammonia in the bottom, and waiting till the ammonia vapor developed the yellow into blue. You can imagine it took a while to do one sheet that way. Since it may take 30 or more pages of construction plans to build one large house, and everybody involved in the construction needs to see some part of the plans, it’s going to take a long time to make all the copies you’d like to have.

Eventually machines made the diazo process more automatic, though there was still a lot of labor involved. These were the machines that made reprographics a standalone industry. Though most of the ammonia was vented outside, the shop still smelled strongly of ammonia. The staff got used to the smell, and Ewan was amused by some female customers who complained about it. He felt that if you’ve ever dealt with a diaper, you shouldn’t be put off by a little ammonia that’s never been associated with a baby’s bottom.

On the other hand, you wouldn't exactly want to bathe in ammonia, in about the same way you wouldn't want to breathe water (another natural substance.) Ammonia is corrosive to skin, eyes, and lungs (just one reason not to leave diapers on indefinitely…)  If combined with bleach it produces poisonous and explosive fumes.  I found an “Ammonia Safety” brochure stating that exposure to 300 parts per million is immediately dangerous to life and health, but then it delicately explains, “Fortunately, ammonia has a low odor threshold (20 ppm), so most people will seek relief at much lower concentrations.”

Antique blueprint machine (sunlight substitute!)

Blueline, whiteprint, or some facsimile thereof...

This is a Photoshop simulation of a blueline.  It looks like it's a negative of a blueprint, though that's not how they're made.
This is a Photoshop simulation of a blueline. It looks like it's a negative of a blueprint, though that's not how they're made.

Architectural copies: bluelines, also known as whiteprints

In the 1970s bluelines began to replace blueprints, probably because the developing process (still bright light and ammonia on ferro-gallate sheets) worked faster on bluelines. Also, being dark lines on a light background, they are easier to read. Bluelines are like a negative of a blueprint; they are blue lines on a whitish background. The difference seems to be in the particular chemicals used on the print sheet; with a blueprint sheet, the light sets the color; with bluelines, light fades the color so only areas shadowed by lines end up colored. Ewan was impressed by his first experience (in 1977) with a blueline machine - you just put a piece of yellow paper in and it turns white (actually yellow and white, but a few yellow lines don’t show much against the white), then you put it in the ammonia vapor and suddenly blue lines appear!

For a long time, bluelines were the cheap option for copies. The process was simple, the machines were cheap and didn't need much maintenance, and the paper was in high demand. About 2006, ammonia started being regulated as a hazardous substance (would that we could regulate out of existence what makes diapers smell of ammonia….) Suddenly, one needed a hazmat license to ship ammonia, and the shipping costs increased to about double the cost of actually making the ammonia. Overnight the cost of ammonia went from about $10 to about $20 a gallon. Since a cylinder of ammonia could last 6 months in a small shop, by itself the price increase didn’t get rid of bluelines, but it was a blow to the process. Nobody wanted to spend that much on ammonia, and many of the manufacturers went out of business, so shipping from distant states became necessary at the same time the shipping costs skyrocketed.

At that time, digital printers were in their infancy and very expensive. But their prices dropped quickly, allowing the cost of bond copies to drop, and people started doing something not possible with bluelines - emailing files to print rather than bringing in originals. Suddenly bluelines went from being the most common, cheapest option to being obsolete. (The diazo process is still alive in Canada; perhaps ammonia is not so regulated there.)

Architectural copies: T-Bond

Not the same thing as a Treasury note. T-Bond, or translucent bond, was a halfway step between originals and prints that allowed one last check before printing. T-Bond was developed to be a cheap, translucent paper that you could print on with a plotter, yet copy from with a blueline printer. It wasn’t as translucent as vellum, so light exposure times were longer; slowing the printing process. But then, it was only intended for running a few “check sets” to get everything checked for accuracy before running the final construction sets. T-bond only lasted 15-20 years. Since it was useful only for bluelines, mills stopped making T-bond about 2008, as machines were printing straight to regular bond paper.

A formation of bond paper

Rolls of bond paper.  The tallest is 36".  The advantage of a roll is that the printer can print a 24"x36" sheet, or a 240"x36" sheet, without changing paper.  Not something you could do with blueline sheets, that came already cut.
Rolls of bond paper. The tallest is 36". The advantage of a roll is that the printer can print a 24"x36" sheet, or a 240"x36" sheet, without changing paper. Not something you could do with blueline sheets, that came already cut.

Architectural copies: bond paper

Just five or ten years ago, though bond copies existed, bluelines were less than half the price. Now the price of toner has dropped, greater demand has brought the price of technology down, and there is less labor involved, and at the same time bluelines have gone up in price. Now bond copies are more cost-effective than going the route of vellum and bluelines.

Bond paper is what everyone would recognize as paper, except that before it’s cut by the printer, it comes in 500-foot rolls. Lifting the rolls is the major physical difficulty of the reprographer’s job today. Bond is printed on by the same xerographic process as your office 8.5x11 copier, and has about the same durability as those copies (except that it’s harder to hold a poster-size sheet of paper in a way that won't rip it.)

Printers, plotters, and giant cameras

There is more to tell you, about printers, plotters, and what you do with a giant camera when it's obsolete. Enough, in fact, that it needs another article to do it justice. That would be Part Three.


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    • GetitScene profile image

      Dale Anderson 2 years ago from The High Seas

      Believe it or not, this question has actually passed my mind on more than one occasion, so thanks for the answer.

    • aethelthryth profile image

      aethelthryth 2 years ago from American Southwest

      You're welcome, GetitScene. Just one of those things to wonder about like why is road-based transportation a shipment and ship-based transportation cargo.

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