Pull any weeds that are poking up through the sandstone pavers. This will make cleaning the patio easier, and weeds will not get stuck in the brush during the cleaning process.
Add the correct amount of cleaning fluid to a large bucket of water following the manufacturer's guidelines. The water temperature will not matter in the cleaning process.
Don a pair of waterproof or latex work gloves -- such as used for household cleaning -- to protect your hands while cleaning the patio.
Dip the stiff-bristled brush into the soapy water. Begin with one section or corner of the patio and vigorously scrub the pavers in a circular motion with the brush, applying cleaning solution freely.
Continue around the circumference of the patio. Additional scrubbing may be needed on areas that are excessively dirty or appear stained.
Repeat the process until the entire patio has been scrubbed clean.
Rinse the patio with clear water. Allow it to dry, and examine the sandstone to see if there are areas that need repeat scrubbing.
If so, repeat the process, making sure to rinse off the cleaner to remove any soap residue.
Prepare a solution of equal parts bleach and water in the bucket. Using a sponge, apply this solution to any areas of the patio that appear black.
If the stain remains stubborn, use the stiff brush to apply the bleach; rinse the area thoroughly.