To remove coffee stains from Onyx kitchen counters, follow these steps:
1. Blot the stain gently with a clean cloth or paper towel to remove as much of the spilled coffee as possible.
2. Prepare a solution of warm water and a few drops of dishwashing detergent.
3. Use a soft sponge or cloth to apply the solution to the stained area.
4. Let the solution sit on the stain for 5-10 minutes, and then rinse the area with warm water.
5. If the stain remains, mix baking soda with water to create a paste, apply it to the stain, and let it sit for 10-15 minutes.
6. Rinse the area with warm water and dry it with a soft, clean cloth.
7. For tougher stains or older stains, you may need to use a commercial stone cleaner or hire a professional cleaner.