Most window ledges, and exterior brickwork, have nearly horizontal surfaces from which water won't quite drain. As dirt and polled accumulates here, algae or midew begins to grow. The longer the surface stays damp ant the dirtier it gets, the worse the problem becomes. If not maintained, you are soon faced with unsightly greenish black staining. It's especially bad on the shady side of the house. The white frames of my windows are especially prone to this along the bottom edge.
Sparying with bleach and water, then scrubbing and rinsing, elininates this ugly mess, but is a lot of work. If only these surfaces could resist soaking up water, AND rinse themselves clean in the rain, or with the hose in drier times.....
Neverwet to the rescue! I can't wait for my 4 kits to arrive so I can apply to the bottoms of all my window frames, and the tops of the brickwork, as shown here:
My kits showed up and I got to work early today, before there was much breeze. I'm happy with the results. I applied Neverwet to the wood strip above the bricks, too. You can see where it was applied if you are looking for it, but it's not too conspicuous.