How do I address tannin bleed if my paint is failing on my cedar siding?

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“The old school painters would say put a good coat of oil based primer on the substrate.” In fact, I was speaking with an older gentleman painter yesterday at the Sherwin Williams store off of 82nd Ave in Portland about this issue and that’s exactly what he said as he proceeded to ask me the question;

“How would you address tannin bleed on cedar shake siding and do you think that peel bond would be a good top coat on top of the oil based primer?”

I told him that the oil would naturally block out the tannin in the wood that is seeking to exfoliate itself out to the top of the surface that is coated. Once you have your sealed coat with the oil because it penetrates deep into the surface of the wood you will solidify and encase that substrate. Whereas compared to latex paint (a water based product) it will not penetrate into the wood as well as oil does rather it will seal itself with the binders in the paint to the outer shell of the substrate.

The rule of thumb is this:
1) You cannot put oil over latex because oil will not stick to a water based paint.
2) However you can put latex on top of oil because you have two solid surfaces in which to bind to. The oil binds to the substrate that you are painting and latex binds to the top of the oil coating.

The reason that tannin bleed is so common with cedar siding or other wood based siding and trim product is this: the tannin’s in the wood seek to bleed through and to the top of the surface and the reason latex paint fails when tannin bleed is present is because the tannin’s will utilize the chemical composition of the water based paint to travel to the top of the surface. That is why you see large strips of latex paint falling off houses when tannin bleed is present. The oil stops it from traveling thus preventing future paint failure for a time. All products deteriorate over time due to oxidization, extreme temperature changes, and normal wear and tear.

The old school painter and I concluded that peel bond would be a great product to put onto of the oil based primer to completely encase the substrate. Then the painting contractor would have to put the top coat on top of the two coats of primer. This is not a cure all for tannin bleed however it is an added security measure to ensure that the bleeding does not work it’s way through the surface of the paint. Peel bond is a water based product but it is also a hard resinous substance that acts like a glue.

In closing, if one product fails the other products that are applied on top of that product will fail as well; it is just like when you want to paint your deck with with Deckscapes from Sherwin Williams, you must first use a stripper and a pressure washer to remove the old stain other wise the top coat of the Deckscapes will only be as good as what is on the substrate to begin with. Choose your products wisely, read the manufacturer specifications and apply your coats per specs. Short cuts never pay off they always take you somewhere you had not anticipated going. Do not go cheap on your paint, pay the few extra dollars for the mid tier to high tier quality paint. It will give you peace of mind knowing that what you are coating has additional chemical properties that will protect your substrate for years to come.

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