Because black is darker than brown, dyeing brown leather black is fairly easy. Changing the color of leather is achieved through the process of staining rather than actually dyeing the material.
To stain leather black, black dye such as TRG, newspaper, a scrubby pad used for cleaning, gloves and the leather are needed. The newspaper and gloves are used to protect the work surface and the dyer's hands. Most color dyes come with a preparer solution and application sponges. Before starting to stain, the leather needs to be clean and dry. It is also important that it be real leather and not patent leather or suede.
The first step is to work the preparer solution into the leather with the scrubby pad. Cover all parts of the leather thoroughly and evenly with smooth strokes. Scrubbing too hard can damage the leather, and gentle pressure is all that is needed. Once the preparer solution has dried, the dye is applied to the shoes in layers until the desired effect is achieved. Thin layers are preferred, as they are easier to build upon and create a smoother, more even appearance. For best results, the layers should dry only a minute or two in between coats, and the leather should dry for a full 48 hours before being used.