Q: Is it true that you can use coffee grounds to make brown hair darker?
A: You can indeed make brown hair dark with coffee grounds. You can make almost any hair color darker with coffee grounds. The color change is not likely to be very lasting, given that it depends on the
hair being porous enough to allow the water-based transfer of tinting into the hair.
The majority of the color imparted is a matter of staining the hair, primarily on the surface of the hair shaft, with whatever portion can pass into the hair providing additional
staining. However, since the coffee grounds are not designed to be permanent color, you may find you have trouble with things like transfer stains on clothing and upholstery fabrics, as well as color bleeding in hot,
moist climates or if you perspire heavily.
Coffee grounds can also present a problem on hair by imparting an irregular color application. You may find better results with doing a cool rinse of very strong coffee (possibly
including the grounds) in order to provide a more even coverage.
And while you can use the process on any lighter color of hair, it does work best when used to deepen a color that is already in the same family.