Linearization of HPR with pt/pd



I’ve been trying to linearize platinum rag for pt/pd with some success but can’t get my curve completely linear. Keith Schreiber has been giving me a lot of help on Facebook which I’m most appreciative of. He believes that what I have now, albeit light might be pleasing in a print. I will share my results so far. Perhaps there is potential to improve my curve more.


First image is the master curve printed for 9 mins with a mixture of 12 dps pd 12 dps ferric 1 drop NA2 1.25%

Second images is the txt file when pasted into the smoother

Third image is the second print made with the first master-lin QUAD

Forth image is the txt file from the second print pasted into the smoother


Fifth image is the 129 step printed with a master-lin-lin QUAD

Sixth image is the resulting txt file copied into the smoother


The difference in density between the second measured values and linear is the difference between 60% humidity and 40% humidity (second print at 40%) as I have observed it. If there was a difference in humidity between the first and second linearization prints than this could very well account for the difference in luminance.

Re-create the exact darkroom conditions of the first target print and you will probably have a much more linear validation print. Make sure to really acclimate the paper to the humidity for over a three hrs.

More humidity = slightly darker mid-tones.




Also, instead of making a new thread, could someone please look at my nozzle check in detail here?

I have bought another 1500W but haven’t unboxed or vetted it with colour cartridges yet.



nozzle check looks fine


Thanks Walker. I have made notes of the temperature and humidity.

The -lin print (3rd image) was 18.2 degrees C and 50% humidity

The -lin-lin print (5th image) was 17.9 degrees C and 58% humidity

The second print had greater humidity so would expect it to be darker.