That is generally not a problem with Ultramar Sail Cleaner.
When sails have those types of soiling, we leave them to soak in Ultramar Sail Cleaner for a few days at our specialist cleaning facility.
After 1 day, we brush and rinse the sail, after which we soak it again for 24 hours. That is generally sufficient. You can repeat the treatment a number of times if necessary.
Naturally, you can also have the sail cleaned professionally by us. Click here for more.