I really don't know what is this useful for, but it is possible and I discovered it accidentally, to develop a C-41 film looking like a B&W film. No discernable color in it, a monochromatic image.
To achieve this result I started using my developer CSS, that contains CD4, to develop C-41. Using the accelerator for B&W film it produced a very weak image, so I decided to use the same accelerator as for paper but the same amount of stock solution at room temperature. Yes, it worked, I fixed the film and bleach, the image I obtained was monochromatic and could be scanned as B&W film giving acceptable B&W pictures.
The next step, and in order to turn this a process that can be reproduced by anyone, without special stuffs, I replaced CD4 by Hair Dye and it worked the same way, the amount of hair dye is maybe more difficult to precise, but I measured some 10ml of that stuff to replace 6 g CD4. Yo this new developer I called CSS-HD, where HD means Hair Dye.
After developing with CSS-HD you may fix normally with rapid fixer and then place the film in a bath of Iodopovidone, sold in the pharmacies as Betadyne in bottles of 500 ml. When it is new it acts very fast, maybe 5 minutes to dissolve the silver, but if used it will take longer and longer, mine needs now some 30 minutes. But no problem, it will not wash out the image, which I suppose is made of dyes but looking B&W.
|Pure B&W and C-41 negative|
|Pure B&W and C-41 negative developed with CSS-HD|
|Picture from athe bove negative scanned as color negative|
|Picture of the first image scanned as color negative|
|Picture of the second image scanned as B&W|