19th century blueprints

[ffutures]

The blueprint process was developed in the 1840s, with the modern black and white process introduced in the 1940s, I think.

I need to know roughly how the original process worked as originally done - I know the chemical principle, what I don't seem to be able to find is a description of how it was actually done. I'm assuming that the plan was clipped over a sheet of sensitised paper and left under a lamp for some time, but beyond that I'm pretty vague on the practicalities. Did they press it under glass? How was it illuminated? Etc. etc.

What I need is the relevant bit of something like a 19th century draughtsman's textbook, or similar. Don't need a huge amount of detail, something like "pressed under glass with a lime-light gas light illuminating the plan" will suffice.

Anyone know?

Comments

[akicif.livejournal.com]

Yeah. Google on "cyanotype". The book we got the "jelly duper" hectograph recipe from (Scientific American Cyclopedia of Formulas, vol II, Standard Literature Co., Calcutta, 1920) has a recipe, I believe, but I think the book's in a box somewhere.

[armb.livejournal.com]

http://www.makepeace.com/About/History/history.htm has this picture and a bit of description.
It says before carbon arcs, daylight was used as the lightsource. How much UV would limelight though glass produce?

[akicif.livejournal.com]

Very little, and the UV is crucial...

[ffutures.livejournal.com]

Thanks- I should have remembered that UV came into it. That helps considerably, means that the relevant bit of the plot has to be done in daylight. Which will give the players problems... ;-)

[ffutures.livejournal.com]

Or I can put in a carbon arc machine, of course. Might be fun. And encourages the adventurers to go snooping at night, when they can run into some different problems to the day (sorry if this sounds like I'm contradicting my earlier post, I've had second thoughts.)