Ink made out of coffee grounds

John Mohr, screen printer in the US, and son-in-law Alex White have developed a new ink variety based on coffee grounds. The idea came from the fact that natural pigments cause stains in clothing, such as coffee, red wine or beet juice, so it should be possible to turn these into inks. To make the ink the coffee grounds are mixed with vinegar and are boiled until it has a similar viscosity to screen inks. The other ingredients are a trade secret. An advantage of using coffee grounds is that it is organic waste which can be recycled, and vinegar is cheap, contrary to usual ink materials. There has been quite some demand for the inks from other screen printers, but Mohr is not selling at the moment. It is not just the inks that are different, the printing process, technique and curing are also different and the inventor prefers not to disclose this.
Currently the inks are being used for printing textiles, but apparently coffee ground ink would also be suitable for paper.