The black streaks in gutters are in the oxidation layer of the paint.
F-13 removes the oxidation and in turn removing the streaks.
Unlike butyl based products F-13 attacks the oxidation not the paint. And unlike butyl-based products that when diluted with water lose their strength rapidly, F-13 is effective at dilution ratios of 50-1. F-13 can be used safely at dilution ratios as low as 5-1. 20-1 dilution normally removes the oxidation with light agitation, making F-13 very economical to use.
F-13 is sold in 1 & 5 gallon pails. Call for larger quantities.
I never downstreamed it, but put it with my solution with the x-jet. it gets some of the black off that way. You really should apply it with a brush. it takes a little elbow grease
F13 is the best out there. It goes a long way because I have to use less then the other brands. I hear there is going to be a price increase so you better get it soon to save…
