Wet the mold stains on your travertine pavers with water from the hose. This prevents mold spores from becoming airborne during the cleaning process.
Fill a bucket with 1 gallon of hot water. Add 1/2 cup of ammonia.
Put on work gloves to protect your hands from direct contact with mold and the drying effects of the ammonia solution.
Dip a nonmetallic scrub brush in the diluted ammonia. Scrub the travertine paver stones to kill the mold spores and remove associated stains. Rinse your scrub brush as needed. Continue to scrub the pavers to remove all the mold stains.
Rinse the travertine pavers with the hose to wash away mold spores and the cleaning solution.
Treat any remaining mold stains with a poultice. Wet the travertine pavers with the ammonia solution. Sprinkle talc over the stains to cover them. Allow the talc to absorb the ammonia solution and remain on the pavers until completely dried.
Remove the dried poultice from the travertine pavers by brushing it into a dustpan with the scrub brush. Rinse the pavers with the hose and allow the surface to air dry.