Is printing pure platinum more difficult than Pt/Pd or pure palladium? And if so, in what way? I've tried it once but hardly got any picture at all. I used the same time, same mixture (except for exchanging the Pl for Pt). Since this is expensive drops I don't feel like wildly experimenting until I know a little bit more.
PS: If a platinum print is a platinotype does that make a palladium print a palladiotype?
Yes, it is harder. The best method for making platinotypes is the glyceryn developing method, frankly I find them too cool for my tests, and far too expensive and time consuming to bother with them.
I think Dick Sullivan has an article in his web site about printing and developing Pt prints. He does have a chapter in his book about this.
I don't have experience with this, but I have heard reports that Buxton paper can make a very successful pure pt print through the conventional printing methods.
As for not getting a print to appear, that shouldn't happen with a pure pt print, I don't believe. The biggest problem that I understand is that the coating will be uneven, and have a poor quality tone, and also uneven dmax. So I suspect you may have had something else that went wrong during the trial.
Some people call palladium prints palladiotypes, but I don't distinguish between the two, because that adds to the naming confusion. I am very forthright about the platinum content of my prints, but I don't like the idea that one print may be a platinotype, and another a palladiotype, simply because of the presence of trace amounts of platinum. I think that is drawing a somewhat arbitrary line in the sand.
Most platinum printers use at most 50% or so platinum, the rest palladium. Some use as little as 10% platinum. I generally call my prints platinum/palladium prints, or pt/pd prints, and in the details will provide the information on the platinum/palladium content.
I consider the term 'platinum print' to be more a description of the process, not the specific metals in the print itself.
I have successfully made nice full tonal scale 100% pure DOP platinum prints by printing on Buxton and using fresh, unused ammmonium citrate developer. The prints were very neutral black, very expensive and not as smooth and creamy as a fine palladium print. There is a reference in Mike Ware's website about why pure platinum papers are hard to find. Google "Mike Ware platinotype" for the address.
Since many of your are alt. process folks, This is a little off topic so forgive me...but how did the photographers of the late 19th and early 20th century expose the Commercial plt. paper they used? Was it still contact, POP - just curious since those days are long gone, but never really thought about it until I was reading this thread.
Put the contract printing frame outdoors and let the sun do the rest.
Simple, cheap and effective.
Some folks still use sunlight although UV light sources are more reliable and consistent.