The 12% SH is what is used. In the states we use a 12.5% mix, that can actually range up to around 15% based on where its made, what type of water was used to make it,etc..... The mixology charts are based on a 12-12.5% strength SH. That would work fine for you. If you are doing metal roofs, I would start at a 1% strength misee what've what kind of results you get, but would not go any higher. I would rather hit the roof with a light second coat if necessary that risk paint damage. As specially some of the cheaper baked enamel finishes that are out there. A Kynar 500 finish should be fine, but did he owner pay for the upgraded paint. You vcan also, bleach wash the metal when done for a uniform shine.

hope this helps, and my wife and I love your island! We have been here times times. Once on our honeymoon 12years ago.

Nigel James wrote:

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Thanks John I will the 1% mix and see how it turns out.

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 How did the 1% turn out for you?