During a teaching career dating from the 1970’s, I have had occasion to view hundreds of Pt/Pd prints. With the beginners, I have frequently found four common errors:
Insufficient Coating. The print is pale and grainy. There is solarization within the image. The cause is not using enough coating solution. When given the choice of too little or too much, do not attempt to economize. For many papers, the coating rod is not allowing the solution to penetrate the surface of the paper. When using a brush, make slow, light strokes until excess fluid accumulates at the edges. This can be removed with a Q Tip.
Insufficient UV Light Source. The blacks in the print are weak. If the negative is not masked, the brush strokes around the image do not reach maximum black (Dmax). This is a common occurrence when using fluorescent tubes. The print must be as close as possible without scalloping the mid and high tones. A good way to test your light source is to use a step tablet printed instead of the negative. One of the steps should reach Dmax. If you do not have a reflection densitometer, test until to two steps at the end are merged. If you can’t do that, you don’t have enough “horsepower”. Replace your light source with higher wattage bulbs or a commercial printer.
Insufficient Clearing. The highlights of the print are yellow. To test, process a piece of the same paper without an image. Compare the two. If there is a distinct stain anywhere in are around the one with the image, not all the iron salts have been removed. This is a frequent problem when using a chelating agent (EDTA) alone in the clearing bath. This is recommended in some literature; however, it may only work in controlled test conditions. If this is a problem, add a bit of sodium sulfate to the clearing bath and warm it to 90 degrees F.
The Negative Contrast Does Not Match the Paper Contrast. The print is dull, with either grayish shadows of dingy highlights. This is more of a problem with film, as it must be developed with more energy and to a greater contrast than if it was meant for silver gelatin photography. With digital negative making this is not as much a problem, but care must be taken to match the negative to the paper contrast during calibration.