Paper Blix - how to test

[Rafael Saffirio]

Hi, how can I test if the paper Blix is ok? I reuse it a lot and never really know if it's still working.

 

[koraks]

For RA4? Take a sheet of RA4 paper. Develop it in a b&w paper developer. Rinse paper. Then blix it. A healthy blix should clear the paper within about 10 seconds.

 

[Rafael Saffirio]

I don't know what do you mean by "clear the paper" in film is kind of obvious, but on paper? it's related to the blue color that the undeveloped paper has?

 

[koraks]

Color paper contains silver halide (silver chloride), which is developed normally with a color developer. The oxidized color developer molecules that are created as a side product, combine with 'dye coupler' molecules that are close to the silver. This forms a colored dye in each spot where some silver was just developed. In the box blix step, the unneeded silver is bleached and fixed away.

I suggest a b&w developer here, which will also develop the silver halide into metallic silver just fine. But the oxidized developer molecules will not pair with the dye couplers, and thus, no colored dyes will be formed. You're left only with developed silver. This isn't much, in color paper, and all you'll get is a medium grey tone. This does require of course that the paper is fully exposed, so do this experiment in normal white light.

Since you now have a piece of color paper with no colors in it, but all of its silver chloride has been developed into metallic silver, it will allow you to assess how well the blix works. After the blix has bleached and fixed away the silver, the paper should come out white. As stated, this process will be very fast in a normal blix that's reasonably fresh, diluted properly etc.

The cyan (Fuji) or magenta (Kodak) dye that you mentioned is an antihalation dye and it will wash out during development. It should be gone after about a minute in the developer (doesn't matter if it's a color or b&w developer).

Of course, the blix will leave some traces of brown/orange in the emulsion, so you have to rinse the paper after blixing it to see if it's really white.

You might want to compare the blixed test sheet with a similar sheet you have not developed, but have only fixed in a regular b&w fixer. This should leave the paper as white as it can be. The blixed sheet should be exactly as white after the experiment.
{other moderator's note - fixed that for you }

 

[Rafael Saffirio]

Color paper contains silver halide (silver chloride), which is developed normally with a color developer. The oxidized color developer molecules that are created as a side product, combine with 'dye coupler' molecules that are close to the silver. This forms a colored dye in each spot where some silver was just developed. In the box blix step, the unneeded silver is bleached and fixed away.

I suggest a b&w developer here, which will also develop the silver halide into metallic silver just fine. But the oxidized developer molecules will not pair with the dye couplers, and thus, no colored dyes will be formed. You're left only with developed silver. This isn't much, in color paper, and all you'll get is a medium grey tone. This does require of course that the paper is fully exposed, so do this experiment in normal white light.

Since you now have a piece of color paper with no colors in it, but all of its silver chloride has been developed into metallic silver, it will allow you to assess how well the blix works. After the blix has bleached and fixed away the silver, the paper should come out white. As stated, this process will be very fast in a normal blix that's reasonably fresh, diluted properly etc.

The cyan (Fuji) or magenta (Kodak) dye that you mentioned is an antihalation dye and it will wash out during development. It should be gone after about a minute in the developer (doesn't matter if it's a color or b&w developer).

Of course, the blix will leave some traces of brown/orange in the emulsion, so you have to rinse the paper after blixing it to see if it's really white.

You might want to compare the blixed test sheet with a similar sheet you have not developed, but have only fixed in a regular b&w fixer. This should leave the paper as white as it can be. The blixed sheet should be exactly as white after the experiment.
{other moderator's note - fixed that for you }

thanks Koraks! that's was very clear. I'll do that test

 

[koraks]

You're welcome @Rafael Saffirio

And thanks 'other moderator' / @MattKing for blixing my post