I have also found that pyro and stained negs sometimes wont even allow an exposure with cyanotypes. Only a nearly perfect pyro neg will yield an exposure, and those cyano's are usually astounding.
Many cyano formulas are highly dependant on the paper you are using, and the ratio of feric amonium citrate to potassium ferricynide (pfc). This is how I make cyano's and they come out great.
1)I use Weston Diploma parchment, it costs more up front, but is cheaper per sheet then Arches and Fabriano.
2) create a 1:1 mixture of pfc solution and feric amonium citrate solution.
3)double coating my paper ( coat, dry, coat, dry). This creates deeper blues.
4) expose for 15-20 minutes (arizona sun).
5) before washing coat it with PFC. PFC is the developing agent and doing this will allow you to achieve deeper blues and more midtones.
6)wash
Ferric ammonium citrate is the light sensative component, and PFC is the developer. If you play around with the ratios, coating, and paper you will find your magic combo. Switching papers in the middle of expirmentation will void all previous tests, unless of course the paper is your control. Try to buy paper in large quantities, because manfacturers change their papers on a whim and without notice.
The "New Cyano" substitues Oxallic acid for one of the chemicals in the original formula, but im not sure which one.
Clear as mud. I know.
Sincerely,