Cross processing, also known as Xpro is a technique of processing film in another film chemical either intentionally or accidentally.
In film photography, it’s the whole unexpected element of surprise when you develop your film. Cross processing makes it even more of a surprise as you can only predict to a certain extent what the results will be like. Additionally, it’s cheaper than getting black and white film.
Here’s our first experiment in cross processing and some timings in an attempt to make a very rough guide as to what results the different times will produce.
Film: Kodak Ultramax 400
Dev: Ilford LC29 (1+19)
Dev Time: 8 mins, 9 mins and 10 mins
Expose all 12 or 36 (depending which film you’re using) shots on the same object with consistent lighting. This makes it easier to compare with different timings.
In the darkroom, cut the negs into multiple strips but not too short otherwise you can’t make a proper comparison. You might have loads of trial and error so you don’t want to waste multiple rolls on this. On top of that, you can always reuse the remaining strips for other experiments.
Here’s the most exciting part - the development time. Use a black and white film timing as a thumb of rule. As for us, we used Delta 400; a 7:30 minutes developing time (with Ilford Ilfotec LC29) and tested various timing around it.
Here are the results (scanned as both B&W and colour negs):
It depends on your preference but our pick was the 9 minutes as the black and white scan comes up a little warmer and has a lot more depth and contrast - the 8 minutes shows up a little flat and greyish and the 10 minutes the blacks had already started to show a blueish/black tinge to them.