Heat marks on Sandstone can be removed by following these steps:

1. Clean the surface of the Sandstone with a damp cloth to remove any surface dirt or debris.

2. Mix a solution of equal parts water and white vinegar.

3. Apply the solution to the heat marks using a soft-bristled brush, making sure to cover the entire area.

4. Let the solution sit on the heat marks for 10-15 minutes.

5. Rinse the area with clean water and wipe dry with a clean cloth.

6. If the heat marks still persist, repeat the process or try using a stone-specific cleaner.

Note: Never use abrasive cleaners or tools as they can scratch or damage the surface of the Sandstone.