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Some chilling first-hand reports from British veterans that were part of the first military nuclear tests. Not told what exactly they were participating in. ~3:30 is scary stuff...
Technical drawings of architectural or engineering designs always seem to consist of white images and text on blue paper. Why?
It’s because of how those documents are made. The blueprinting process was developed in the mid-1800s, when scientists discovered that ammonium iron citrate and potassium ferrocyanide created a photosensitive solution that could be used for reproducing documents.
The process goes like this: Someone creates a drawing on translucent tracing paper or cloth. The drawing is placed over a piece of blueprinting paper, which has been coated with a mix of ammonium iron citrate and potassium ferrocyanide from an aqueous solution and dried. When the two papers are exposed to a bright light, the two chemicals react to form an insoluble blue compound called blue ferric ferrocyanide (also known as Prussian Blue), except where the blueprinting paper was covered, and the light blocked, by the lines of the original drawing. After the paper is washed and dried to keep those lines from exposing, you’re left with a negative image of white (or whatever color the blueprint paper originally was) against a dark blue background.
The technique was faster and more cost-effective than hand-tracing original documents, and caught on as an easy, inexpensive way to reproduce drawings and texts. After carbon copying and copier machines took on that job for smaller documents, architects, engineers and shipwrights continued to use blueprinting to copy their large-scale drawings. More recently, the diazo whiteprint process and large-format xerographic photocopiers have largely replaced blueprinting even for these specialized purposes, and many “blueprints” are now black or grey lines on a white background. Xerograph just doesn't have the same ring as blueprint for a shorthand description for a master plan, though.
Originally Posted by srvy:
Hardly anyone uses blueprinting now.
In my personal version of buggy-whip making, I took drafting every semester in HS, and by third-year we were instructed and authorized to create blueprints of our work.
CAD existed but computers were still in the Commodore 64, IBM 8088 stage, so it was still a couple of years from being practical for instruction, so I got NONE of it.
I try to salve the pain of obsolescence by telling myself that knowing the hands-on practices of observation, measurement, and communication still retains value. [Reply]
The amount of time you have to escape a house fire has greatly decreased in the past few decades:
30 years ago you had about 15 to 17 minutes to escape a house fire.
Today, you have about 3 to 5 minutes to escape a house fire.
The reason the time to escape a home fire has decreased so much relates to changes in the types of furniture and other contents in today’s homes, including more plastics and petroleum based products. Changes in how homes are designed (open floor plans, larger rooms and higher ceilings) have also changed the chemical composition of the fire and greatly increased the speed at which it grows. [Reply]
Originally Posted by Fish:
The amount of time you have to escape a house fire has greatly decreased in the past few decades:
30 years ago you had about 15 to 17 minutes to escape a house fire.
Today, you have about 3 to 5 minutes to escape a house fire.
The reason the time to escape a home fire has decreased so much relates to changes in the types of furniture and other contents in today’s homes, including more plastics and petroleum based products. Changes in how homes are designed (open floor plans, larger rooms and higher ceilings) have also changed the chemical composition of the fire and greatly increased the speed at which it grows.
I'd guess building materials have changed, too. Lots of hollow walls with nothing but 2x4s and drywall today where you'd often see brick, plaster, or wood paneling in older homes. [Reply]
