Exposure time and contrast of Kallitype

[stefano_ber]

a question about the exposure time of the Kallitype
In your experience, if the conditions remain the same (sensitizer and developer), would the exposure time of the same film always remain the same? Because sometimes it changes to me. Is it sensitive to humidity? I knew that only POP prints had this problem.
Furthermore, as regards the final quality of the print, do you prefer to vary the contrast with potassium dichromate or ammonium dichromate?

Thank you!

Stefano

 

[Andrew O'Neill]

The base exposure should remain constant. This exposure is determined by doing minimum time for maximum black test, with a piece of unexposed but developed film in contact with the sensitised paper. Negatives need to be developed to match the DR of the kallitype process. But it's never perfect, so sometimes we need to add a dichromate to increase contrast.

 

[stefano_ber]

The base exposure should remain constant. This exposure is determined by doing minimum time for maximum black test, with a piece of unexposed but developed film in contact with the sensitised paper. Negatives need to be developed to match the DR of the kallitype process. But it's never perfect, so sometimes we need to add a dichromate to increase contrast.

thank you Andrew!
I don't use digital films but analog ones. Does the same procedure apply? I guess it depends on the type of film used due to the transparency of the support.
Which method do you prefer for contrast?

 

[Andrew O'Neill]

It applies to both digital and film, at least for me. For film, for more contrast, I use ammonium or potassium dichromate, at varying strengths. I've rarely run into a print where I've needed less contrast. Giving a little more exposure can help, but too much and solarisation can happen. Gold toning can mask most of that.