Re: Olf Fartism Strikes Again

>still remember the smell and blue fingers of the ammonia based
>process. was the cyanide process similar?
A lot more poisonous. Both processes were photographic with the tracing acting as negative. Honest-to-god blueprints used the same kind of development but the coating contained potassium ferricyanide which is the poison. After a couple of hours making diazo prints the ammonia fumes got a little nauseating, too. Neither was permanent under exposure to sunlight. You could mark on diazo prints much easier than blueprints.

Christopher Wright P.E.    |"They couldn't hit an elephant at
chrisw@skypoint.com        | this distance"   (last words of Gen.
___________________________| John Sedgwick, Spotsylvania 1864)