Reply To: Sapwood for external door
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The pictures you showed are a bit rough in texture, making harder to determine if your oak is in the white or red oak families. Red oak is ring porous and absorbs water easily, making it not so rot resistant. White oak is quite rot and weather resistant. Two ways to tell are to plane the ends of the wood Red oak will have obvious open pores)you can actually take a sprig of the wood and blow through it into a glass of water. With red oak you can blow bubbles.
A boat has a lot more water contact than a door. Properly protected and finished six sides, some sapwood is acceptable if you can make the colors match. If the door has been there years with no finish and is still sound, you are probably fine. Consider yourself lucky.
As to reestablishing the color, I’d first wash the oak door with an oxalic acid wash to bleach the wood even. Then try a water based dye stain followed by a light sanding, The water based stain can be controlled by thinning or applying more to get the light and dark oaks more the same. Follow with a sanding sealer ( 1/2 pound mix of shellac will do, followed by a sanding to knock back the fuzz from the water based stain ( sand most of the sealer off but not the stain) and finally a oil gel stain topcoat. Wipe that off after a couple minutes. How long you leave it on matters a lot.
I’ve had good luck with General finishes products. They seem predictable.
You can always stain darker. You can’t stain lighter. I then follow with a couple coats of thinned shellac, followed by 0000 steel wool to get the surface smooth. If you use amber shellac or darker ( thinned) you can sometimes even out the color. Stop before the grain gets muddy. If you get too dark or don’t like the effect, you can wipe the dark shellac off with alcohol. This is your second shot at experimenting.
For a final finish I’d use a spar varnish, NOT a poly varnish. Most poly varnish has no UV inhibitors that protect the finish, and poly varnish isn’t renewable with a simple light cleaning and new coat. Poly doesn’t stick to hard poly very well. You will eventually get flaking and have to strip and start over.
Spar varnish, on the other hand, does offer UV protection and is renewable with a OOOO steel wool going over followed by a fresh coat. Get a marine spar varnish, not the box store kind. ( Interlux, or my favorite, Epifanes) It’s frightfully expensive but has much higher solids content. For a door, I figure a pint per coat. $20-$30 per pint. Thin as directed at least 3 coats. Lightly sand between coats. Get into the zen of it.
It will probably be too glossy. When thoroughly dry, wax with OOOO steel wool to knock the sheen back. Stand back and admire. And I’ve found that if the finish is sound, you can make a wiping varnish to renew the sheen and hide scratches on a sheltered door. Wipe off the wax with mineral spirits first. I use 50-50 walnut oil and varnish. A very thin coat is enough. That only takes a few minutes and dries in a couple hours. Mind the weatherstripping doesn’t contact a sticky door.