I've seen several posts recently mentioning a "cling film technique", there appear to be different ways of doing it, so I though I would try it myself.
I used a foam paint brush with clean water to totally saturate the plain white card. Using a piece of cling film, I dabbed on various shades of Distress Oxide Ink pads, lightly scrunched the film then positioned on top of the wet card and left for a couple of hours. I then lifted the film off and blotted any damp puddles with a corner of kitchen roll then left to dry.
I did the same using Distress Oxide Inks spray, which resulted in stronger coloured backgrounds.