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A few years ago, the is discussion led to the idea of using Armor All and copper sulphate combined and applied to a roof. Armor All was used to trap the copper sulphate on the roof and make it resistant to washing away for a period of time.

Basically though,..I get approximately 4 years on a roof job using SH. That is long enough to satisfy customers and keep it a viable service.

I suppose it all depends on what you want to sell,..and what you're willing to do to sell the extra service.

Jeff