To waterproof Black Gold Marble floor, you can follow these steps:

1. Clean the Floor: Start by thoroughly cleaning the marble floor with a pH-neutral marble cleaner. Remove any dirt, dust, or debris from the surface of the floor. Rinse well and dry.

2. Repair any Damages: Inspect the floor for any cracks, chips, or damages. Repair any damage using a marble repair kit or with the help of a professional. Ensure that the surface is smooth and even.

3. Test the Sealer: Before applying any sealer to the entire floor, it is essential to test it in an inconspicuous area to check for any adverse reactions or discoloration. Follow the manufacturers instructions for time and coverage.

4. Choose the Sealer: Select a high-quality marble sealer that is specifically formulated for waterproofing marble. Look for a penetrating sealer designed to protect against water, stains, and other liquids. Consider asking a professional or a specialist at a home improvement store for recommendations if necessary.

5. Apply the Sealer: Use a clean, lint-free cloth or a paintbrush to apply the sealer evenly across the surface of the marble floor. Work in small sections to ensure thorough coverage. Avoid applying excess sealer as it may lead to surface discoloration.

6. Allow Drying Time: Allow the sealer to dry completely as per the manufacturers instructions. Typically, it may take several hours or even a day for the sealer to dry thoroughly. Ensure the room is well-ventilated during the drying process.

7. Apply Additional Coats: Depending on the porosity of the marble and the specific sealer used, you may need to apply additional coats. Follow the manufacturers instructions for the recommended number of coats, application process, and drying time between each coat.

8. Maintain Regularly: Once the sealer has fully cured, make it a habit to clean and maintain the marble floor regularly using a pH-neutral cleaner. Avoid using acidic or abrasive cleaners that can damage the sealer.

Note: It is important to remember that no sealer can make marble completely impervious to water. While it can provide a protective barrier, promptly wiping up any spills or moisture on the surface can help prevent any potential damage.