I was astonished that my white filters didn't stain right away. But they didn't, not sitting in the yogurt quart jar for a week, or in the compost heap for several weeks.
It was like the old black and white movie where someone invented a cloth that never got dirty: no matter how old, they always looked like a white spotlight on a tuxedo shirt. As if the paper were not only bleached, but also stain-proofed. It seems impossible, but that's what I saw.
Coffee stains everything else!
