Remove any existing finish from the cabinet, using an appropriate method. Protect floor with newspaper and wear a dust mask. Use medium grade sandpaper, followed by fine grade to provide a smooth but open-grained surface. Wipe the cabinet down with a damp cloth to remove any remaining dust. Allow it to dry completely.
Brew the coffee and let it cool to room temperature. Always use fresh-brewed coffee, ground or instant. Stale coffee will oxidize and provide a less effective stain.
Apply the coffee with a clean paintbrush or by dipping a cloth into the coffee and rubbing it on. Keep applying the coffee for about 15 minutes to keep the wood wet and the grain open to absorb the stain. The coffee glaze will produce a varied effect; some areas will take the stain better than others. This color variation evens out as the cabinet dries and will look completely natural.
Assess the color once thoroughly dry; apply more coffee stain if required. Make a fresh brew of coffee for each application. Light wood, such as white pine, will darken quite easily but dark colored wood will show less of an effect.
Apply one or two coats of water-based varnish to the cabinet, sand lightly between coats. Allow the cabinet to stand for 78 hours before use for the finish to cure. Alternatively, seal with a natural beeswax polish.