Backpriming T&G wood


Hello,
When backpriming T&G solid sawn wood, is it best to prime the tongues and grooves, or not? On the one hand, sealing all sides is good; on the other, it would be easy to get excess paint in the corners which could interfere with the mating of the T&G. But the groove is typically 1/16" wider than the tongue, so perhaps that's not really an issue.
Thanks, Wayne
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Wayne Whitney wrote:

My father always objected to back priming when the back would not be subject to moisture. Wood likes to breath. There will always be some moisture penetrating the finished side, If everything is sealed it tends to come out wherever and that might mean the finished side and it may will take the finish with it.
--
Joseph Meehan

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A couple comments:
I believe that latex paint is more vapor permeable than oil base paint. So perhaps the analysis above only applies to oil based paints.
Also, the main argument for finishing both faces is that otherwise the differential rates of moisture movement through the two faces when the wood is exposed to a shift in ambient humidity could lead to differential rates of expansion/contraction, i.e. cupping. If the wood is unrestrained then this cupping should be transient, but if it is restrained then compression set on one side could make the cupping permanent.
Cheers, Wayne
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