This article discusses the "magic" moment, ie when you already have your negative, paper, materials and everything is ready to make the fine print. What follows is not how to do it, it is how I do it, and it is intended for beginners. Your technique may vary. The article, however, asserts that you will be printing in platinum / palladium or just palladium, from a digital negative, using Potassium Oxalate as a developer.
Coating the paper.
Start mixing the solution in a short glass. For an 8×10 "print I use 15 drops of ferric oxalate, 15 of palladium / platinum, and 1 drop of Na2 at 2.5% Many books recommend more solution. I do not think it is necessary, for 30 drops of solution will cover an 8×10 "print very well even with a brush.
You may think that the percentage of Na2 should vary depending on the print and one can not just say "one drop of Na2 at 2.5%". This is indeed not true, for you already have the correct contrast sorted in the (digital) negative, hence ALL you images will print well with just ONE drop of 2.5% Na2 contrast agent. Also, ALL your prints (on the same paper) will print with the same exposure, in my case this is ~ 4 minutes but this time of course depends on the UV unit and you will have to find your own time.
With digital negatives, the printing process itself is almost routine and can not go wrong, because the negative is, in fact, spot on and perfect. Of course, getting this 'perfection' in the negative may take some time and tweaking.
Also, some may think that just one drop of 2.5% Na2 may be too little and the prints will show some fogging. I have never experienced this problem, probably because of the small quantity of oxalic acid which I add to my ferric oxalate solution. Keep in mind that Na2 is a very powerful contrast agent. If you want, you can use one drop at 5%, this will also leave some room your should print show too much contrast. If you decide to do so, of course, you will have to modify slightly your Photoshop curve. Personally, I have always been using one drop at 2.5%.
Once you have the solution ready, fill / empty the syringe in the glass 3 or 4 times to mix the solution thoroughly. Get the brush and pour some little water on it, then dry it with a tissue but be sure to leave it a bit moist. Take the sheet of paper and the negative that you are going to print. Lay the negative on the paper and look at it for 5 seconds to make a visual image of where to coat (this is sufficient, you do not need to draw amateur pencil lines or make templates to limit the coating area). Remove the negative (put it back in its envelope and do not leave it exposed near the coating area or small drops of solution will inevitably land on it when coating) and get the brush, with the same hand also get the syringe. I am right handed so I quickly squirt the solution in a line from left to right along the long side of the paper.
You want to form a nice long bead in the center of the paper, this does not work well if you pour the solution from a glass, hence the syringe (no needle of course). Immediately pass the empty syringe to the other hand (which you will also use to hold the paper down too) and start coating in large vertical stripes first, then horizontal and repeat until the entire area (of which you still have a visual image in your Mind) is perfectly covered. No need to push hard on the brush, its own weight will be plenty.
Be accurate and swift in this procedure, for the goal is coating the paper well with less solution as possible of course. If you end up with huge black borders it obviously means that you are over coat, if the negative can not fit the covered area it means, of course, that you are under coating. Some experts recommend a chemical called Tween20 to facilitate coating, which has always proved to be totally useless. You can get yourself started practicing with something not expensive such as coffee and photocopy paper. Soon you will be able to cover the entire area leaving a nice and thin black border all around the print all by eye.
After this is done, leave the freshly coated paper to dry (I cover it temporarily with a cardboard lid for protection from light, bugs, dust etc). After about two minutes (just to allow the solution to penetrate the paper) put the sheet under the hot drier for another two or three minutes. Do not leave the paper to air dry too long or the solution will 'go through' the paper and the image will look weak. On the other hand you must allow some time before hot drying to allow the metals to penetrate and give the print the famous 'platinum presence'. You will have to experiment a bit with these times, also depending on your climate and time of the year, humidity etc., not that it makes such a huge difference anyway. Just, as always in a darkroom, be consistent and keep following the same procedures and timing.
While the paper is drying, you can wash glass, brush and syringe, ready for your next print. What if you break a rule and do not wash them: in this case, your next print will require (considerable) less solution, like 11 drops instead of 15, a great way to save money. This is possible because, as said, all our prints use the same mix (contrast agent etc). Or, you can group the prints with the same contrast / mix before starting your printing session. However, even though it does work, I do not do this, because when I started there were no digital negatives and each negative would of course require its own (different) contrast mix, and I am used to that procedure. Also, it makes me uncomfortable (sort of cheating?). Consider this not a recommendation but a possible working trick to save some money especially when making additional prints from the same negative. Be careful: whatever your procedure, if the print has not received adequate coating, it will look quite anemic and weak. You can experiment making a test print (maybe along with a step wedge) with more or less solution and see if there is any difference.
Once the paper is dry, briefly inspect it, it should exhibit a nice and uniform orange coating. If there are flaws, like maybe small dots, you will take care of these when spotting. In fact, whatever you see on the covered paper now, there is little you can do about it. If you see a bristle from the brush, you can try to lift it off with a scalpel, again, when the paper is dry. I have never experienced this with my Grumbacher brush though. With Cranes paper, my favorite, depending on the batch, sometimes some small areas look lighter when seen through the light. These spots will disappear once the print is made and dry, so do not worry. If there are major flaws, like thin uncoated areas, it might be a good chance to experiment with double coating, for example.
Now place the paper on the contact printing frame, then the negative and the glass and put them inside the UV unit for the required exposure. During this time you can coat another sheet for your next print or, if you are not so busy, just relax.
Now it is the moment for some magic. Just take the exposed sheet of paper and slide it swiftly in the developer tray from one side, you want it to "cut" through the surface of the solution. Some people keep the solution in a jug and splash it over the print but honestly I can not even understand the reasons to go through this extra step. Others tilt the tray to leave a dry area at the bottom where they lay the paper and then allow the solution to cover the paper, I would not do this either. From now on, please keep in mind that we are working with water color paper that is not recommended to stay almost one hour in chemicals and running water, since it will become very fragile, so take extreme care when handling. Once the sheet of paper will be submersed, the image will develop immediately.
It is generally recommended to let the print in the developer for one to two minutes, I have found that one minute is sufficient and there is no change in the image keeping the print longer than that (this is not silver printing). I have, however, standardized my procedure to 1.5 minutes. The temperature of the developer will have some effect on the final color (higher temperature = warmer color). I have a sort of big dish warmer under the tray even though I use it, because I like the color I get at room temperature with the added benefit that of course the developer will last longer.
After developing the print, lift it and drain very well and take it to the washing tray for a quick wash, this will make the clearing solution last longer. Then we can start the clearing process passing the print from the first to the third tray (4/5 minutes each, rocking them gently every now and then, especially in the first tray) and finally in the washer for no more than 30 minutes. This clearing procedure is good with citric acid, three teaspoons per 1,5 liters. If you use Kodak hypo clearing agent, I believe three minutes in each bath will suffice. After washing, drain well, then get two sheets of blotting paper and gently and carefully absorb all the water from the print. If you press too much the blotting paper will leave marks in the print. At this point the print is ready for air drying on a mesh (face up, another difference from silver printing).
You can inspect it but keep in mind that once dry it will be considered darker, especially the highlights. If the print looks OK wet, you can be sure that it will look too dark once dry. If you see any flaw in the print (black spots, dust, hair or whatever) do not even try to touch its surface with anything because it will leave a mark on it. Put the bloting paper sheets to dry too, do not use them again with your next print. By the way, do not buy those blotting paper books, they tend to develop mold and will become all warped. Buy loose sheets and take care of them, or replace often. After this, you will be ready to make another print, or if you are done, just put the developer back in its bottle and wash the trays. Every printing session, I also clean my contact printing frame glass.
I usually leave my prints to dry overnight. If you are in a hurry, you can dry a print in the same hot air drying unit used with coated sheets, but it will not dry very flat and also it will stress the paper fibers. I hot dry sometimes to quickly evaluate some prints. After the print is dry, you can assess it. The first print from a new negative, of course, needs a full evaluation, additional prints from the same negative, if you are consistent in the darkroom, will only need a quick check. To evaluate, I mask the black borders with an off white bevel window cut sheet from my usual mounting board, to avoid ruining the shadows in the print. I generally check the print in average light conditions, certainly not under a strong fluorescent light and definitely not in the darkroom. If I am happy with the print I proceed with spotting (once flat), if I am not, it means that there is something wrong with the negative so back to Photoshop to make another one. We are chasing to get a good, easy to print negative. I use Pictorico film which is not particularly expensive, so I find more convenient to make another negative.
Of course, you still have some control in the darkroom. If the print is flat you can use more contrast agent, if it is too dark or too light you can change exposure time a little. If the print is too punchy and contrasty the only solution is to make another negative. If there are areas in need of burning or dodging, which is an annoying procedure when contact printing under UV, it is better to do the corrections in Photoshop and make another negative.
Sometimes you will find that technically the print is OK yet it does not work, which means that you must develop an aesthetic correlation between what you see on the screen and what the finished print will look. In some way, what Ansel Adams famously called "pre-visualization". His method was pre-visualizing the actual print when looking at the camera's ground glass, in our case, it is something similar but we are looking at a computer screen. A last thought on assessing platinum and especially palladium prints: the print should be beautiful and with good "presence". The shadows should be thick and juicy, and the highlights should almost glow, ie be "light". If this is not the case, often the problem is that you are printing too dark. Often people, coming from other printing processes, especially silver, follow the same visual accomplishes that were used to, with harsh contrast and deep shadows, which in my opinion is wrong in pt-pd (although there are many different schools on this). Often the mid tones are printed too dark, they get muddy, easy to fix with Photoshop. Especially with portraiture and landscapes try to stay less contrast than you think, more "delicate".
Coming to platinum printmaking from silver, I immediately found the darkroom part of the process far more relaxing and enjoyable. If you are a photographer considering switching to platinum (or any other alternative process) but still uncertain, I would consider this a big plus in my decision.