Where do you work on your sails? Because of the proportions of boat and sail which have been fixed by time-tested rules, it is a truism that the foresail will be much too big to fit on the deck, regardless of the size of the boat. So, if you had to work on your foresail, where would you do it?
For us, the answer is some clean grass - grass not recently cut (and therefore littered with clippings) and free of dog-exhaust. Admittedly, this is not always easy to find. Yet, because we had to have our foresail off of the boat for our just-completed haulout, this weekend was the perfect time to find some clean grass and go after the algae and mildew growing on the sunshield, and to do some minor repair.
Here, Jane is taking her turn at playing seamstress, while I am taking pictures instead of getting out the vinegar and starting to work on the sunshield. (Non-sailors: when the sail is rolled up on the forestay, that green border is all that is exposed - it's there to shield the sail from UV-deterioration. And to provide a home for wayward algae.)
White vinegar is an excellent treatment for algae and mildew. Being a 5% solution of acetic acid in water, the pH is low enough to kill off the single-celled life forms, and yet it is weak enough to cause no harm to the fabric. Bonus: both the water and the vinegar eventually evaporate - no rinsing is required.
To prevent colonized algae and mildew from surviving the onslaught of the vinegar by sacrificing their outer members to protect those inside, it is good to break up the colonies while doing the vinegar treatment. I used a small brush, originally designed to strip cornsilk off of raw corn-on-the-cob - it is soft enough to be kind to the fabric and the thread, yet it does yeoman duty in destroying colonies (look for one in your grocery store).