Ware recommends using a dilute acid bath for the "new cyanotype" process rather than the simple Potassium ferricyanide/Ferric ammonium citrate recipe; and he also specifies a mineral acid (hydrochloric or nitric). I expect that citric acid has crept into the ready-made products' instructions as it's safer to use all round. I remember trying the Fotospeed kit and then going back happily to home-made.
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