Stability of calibration in Pd process


My calibration is now working fine and the first negative gives same result as on screen :slight_smile: I’m happy.


However, how sensitive is the process to solution #1 from Bostick and Sullivan? I would prefer to buy their Ferric Oxalate by gram and mix this solution myself. It easy to buy this from them but they will not tell me amounts (ok they say 27%) and if they have further additives to make it last for long time.

If I just buy FO and mix it to 27% will this change my calibration? Or have they added Oxalic acid as Dick Arent<i><b>z</b></i> and other says is an option. Will this as well change calibration?

I hope understand if I put efforts in calibration I want to have control of my chemistry as well. Otherwise it will be cumbersome.


Any opinions?




They do not add acid. I don’t know the percentage but Jon does (and others on this list no-doubt). I will let them chime in.




PiezoDN negative is a very stable negative making process. It is not sensitive to minute changes in chemistry as is using color inks to print negs. PiezoDN has a very wide latitude because of the amount of overlapping monochromatic inks none of which are peculiarly more or less sensitive to UV as are the different color inks that make up a color ink neg. If your experience has been in the past that you needed to recalibrate to the least minor change in your chemistry or environment, you should find that you can go much wider in swing with PiezoDN negs without visibly throwing off the print.

Ferric Oxalate, at least in the data we have recorded is one of the most sensitive of the solutions you are using. So, we mix FO every 60 days. It is SOOOOOOO CHEAP to buy that you should not even consider whether you should try and extend its life. We are hitting dMax of 1.41 to 1.51 regularly depending upon paper. Getting such good black, and knowing it is partially dependent upon the FO - we don’t worry about discarding FO in favor of fresh. We removed the FO aging factor from our darkroom.

Having said that, humidity is probably the single most important factor in standardizing. Calibration therefore, is to first control your standard environment - otherwise you may be chasing calibration all the time and making very few prints.

Our practice is to re-calibrate when we mix new FO. On any given day or even late in the night - I can go into our darkroom and make predictable prints. When we re-calibrate we coat two small sheets each of our 4 standard papers. One for the target and one for the confirmation print. We can do it all in 4 hours or so and our darkroom is back to harmony. We do not need to chase minute environmental changes because we more or less control our humidity and temperature.


I order my FO from B&S in dry form in the small bottles and then add water to them if older than 60 days. Very cheap and guaranteed cheap. Jut remember to request they they ship the FO dry as it’s not one of the options on the website.


Thanks William. Yes I know but still I want to have control of the chemistry. When I by #1 solution I’d like know whats in it, if the go out of business etc.




When you re-calibrate with a new mix of FO, do you use the master curve or do you use the latest working curve for linearization/calibration?




B&S has always sold dry ferric oxalate powder. It has always been on the website. You must be looking in the wrong place.

  • Pre-measured:
  • Bulk:


B&S does not add anything to their ferric oxalate, dry or liquid.


Thanks Keith,

So there is just FO.

Dick Arentz recipe 27% or 15 gr FO to 55 ml distilled water.

And I can by the power/crystals myself from them!





@art You use the latest curve.


Thank you for your answers Jon and Walker they will help me a lot to make a my workflow stable over time.

I’ll later this year change the inks to be latest version to benefit of this long latitude and UV properties.