Another print I made this weekend – Key Bridge, in palladium. This is a 5×12 negative from my Canham. For the technically minded, I used a circa 1949 Kodak Commercial Ektar 12″ lens for the shot. It’s a very sharp lens with pleasant rendering, and a good match for the subject matter. I also want to talk for a second about the printing – this is a pure palladium print, with a touch of NA2 added for contrast. Sodium Platinum (NA2 for short) is a contrast agent you can add to a palladium print to boost the contrast if required. NA2 is very powerful stuff – a tiny bit goes a long way. In this case, I needed just one drop of 2.5% NA2 added to the 12 drops of Palladium and 12 drops of Ferric Oxalate sensitizer. NA2 comes from the manufacturer in a 5% strength solution, so you can see how little was needed to give the print some snap.
If you are using blended platinum and palladium, or trying to do a pure platinum print, and are in need of a contrast boost, you cannot use NA2 as a contrast agent – the platinum in it binds with platinum in your paper and what ends up happening is you reduce your highlights, blowing out detail, without actually increasing contrast. If you are using a blend, or pure platinum, you have several options – you can boost the contrast with a different additive, such as gold chloride, you can pre-coat your paper with fumed silica, or you can use a dichromate infused developer. I prefer adding a contrast agent into the emulsion rather than in the developer, because to do the infused developer route, you’ll need to have six or eight bottles of developers with different concentrations of contrast agent, and then you’ll have to play with chemistry to mix up replenisher for each developer concentration as it gets used. That realistically means keeping twelve to sixteen bottles of developer around. The downside to additives to the emulsion is that most of them will alter the color of the print. Gold Chloride will do anything from slightly cooler gray tones to eggplant/aubergine tones, depending on how much of it you use. Sodium Tungstate will actually reduce contrast in the print, and give you reddish brown tones. You can use dichromate in the emulsion as an alternative to the developer, but you must be careful in handling the undeveloped print as dichromate is toxic.