I am building a victorian style porch in south central Pennsylvania. I have purchased western red cedar porch posts that have some knots. The knots do not appear sticky like pine knots sometimes are. I am planing to paint the posts with Benjamin Moore alkyd primer and 100% acrylic topcoat. Does anyone have an opinion about whether I should shellac the knots before painting? Is there any downside to shellacing the knots unnecessarily? My current plan is to coat knots with amber shellac just to be safe.
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Consider me ignorant since I haven't put shellac of WR Cedar knots, but if you go over to the Fine Wood Working site, or look in some of the finishing books, it appears to me that a large percentage of folks would agree that shellac is the way to go to seal knots. I've used wash coats of shellac, and then put poly over the surface, and have been pleased with the results.
Besides the time and material input there is no downside. When I did my apprenticeship in Europe we had to first wash the wood knots with denaturated alcohol, let it dry for half a day and then seal it with shellac before priming/finishing.
I'm unclear if you are shellacing the part you are painting or the rest of it? If its the part you are painting, there's not much point I can see in using amber shellac. Further you should use a dewaxed shellac if you are going to apply a different finish overtop of it - like poly or paint.
If you just want to get rid of the knots before you paint you can try zinsser BIN which is a shellac based primer.
Sorry, if I'm misunderstanding you.
Prime with Zinser shellac based white primer.This primes and seals,no need for a separate primer.
mike