Hello, I just recently started in Pt./Pd. Printing, and I ordered the Platinachrome kit from the japanese Ilford. According to the data sheets, it is "normal" Na2-Pt./Pd. chemistry, with Ammoniumcitrate as developer.
First, I wanted to determine my basic exposure time, so I just coated a small piece of Hahnemühle Platinum rag with the chemistry, and after it dried, I placed it in the contact frame, half under an unexposed but processed negative, half "naked".
I then exposed it using 4 15-watt UV-tubes from about 5cm distance, and used a piece of black matte board to mask in steps of 1 minute, 2, 4, 8, 16. After processing and drying the paper, I can see the difference between the area under negative and not disappearing around 4 minutes, but even at 16 it is not black, only some sort of "middle-dark" grey. In fact, there is not much of a change between 4 and 8 minutes, and none visible between 8 and 16.
What could cause such a problem?
I already tested the pH of the developer, it is 5.0, which should be fine. And the UV-lamp is certainly fine, as I printed salted paper with it just a few days earlier (exp times ~15 min., but salt takes much longer than pt/pd, right?)
Could I be using too few coating chemistry? I took the drop count from the Bostick and Sullivan tutorial and scaled it down to 5x7 inches. For 5x7, I used 5 drops each of Pd and FeOx, and 2 drops of Pt.
Could this be too few? (I am using a hake brush, but in the video they used brush coating as well...)
What else could lead to failure in obtaining real blacks?
First, I wanted to determine my basic exposure time, so I just coated a small piece of Hahnemühle Platinum rag with the chemistry, and after it dried, I placed it in the contact frame, half under an unexposed but processed negative, half "naked".
I then exposed it using 4 15-watt UV-tubes from about 5cm distance, and used a piece of black matte board to mask in steps of 1 minute, 2, 4, 8, 16. After processing and drying the paper, I can see the difference between the area under negative and not disappearing around 4 minutes, but even at 16 it is not black, only some sort of "middle-dark" grey. In fact, there is not much of a change between 4 and 8 minutes, and none visible between 8 and 16.
What could cause such a problem?
I already tested the pH of the developer, it is 5.0, which should be fine. And the UV-lamp is certainly fine, as I printed salted paper with it just a few days earlier (exp times ~15 min., but salt takes much longer than pt/pd, right?)
Could I be using too few coating chemistry? I took the drop count from the Bostick and Sullivan tutorial and scaled it down to 5x7 inches. For 5x7, I used 5 drops each of Pd and FeOx, and 2 drops of Pt.
Could this be too few? (I am using a hake brush, but in the video they used brush coating as well...)
What else could lead to failure in obtaining real blacks?