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Discussion Starter · #1 ·
Any thoughts about how best to sand old oxidized/flaking polyurethane off uneven wood molding surfaces on our wooden front door so I can apply a solid color acrylic/latex exterior dark paint (which I hope will last longer). I'm looking for some sort of sanding fixture/tool so I don't have to do this by hand. Please see pic of the front door that needs
attention. All comments are welcome.
Window Wood Textile Fixture Material property
 

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Caveat: I'm not a professional! That said, I'd go with a chemical stripper and a stiff nylon brush. I fear sanding, scraping or brushing with metal bristles would mar the molding detail, and heat stripping risks melting the glass solder joints.
 

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You can chose between a mechanical approach or a chemical approach or both.
Sanding is best on wider flat surfaces, but scraping will work prior to that to remove most of it. Scraping is best in fillets and curves where a sander won't fit., A wire brush or wire wheel may save some hand labor.
Then after the mechanical approach you can use a chemical to soften and loosen what remains. The newer chemical don't have the strength of methylene chloride of times past and don't work as well which is why I suggested the above methods first.
Regardless, it won't be much fun and wear masks and gloves for protection.
A heat gun will also work to soften the finish without damage to the surface or the leaded glass. It's temperature is not that high like an open flame.
Paint and varnish are "film finishes " and don't penetrate the wood pores like oil or gel stains and finishes, so they require more extensive maintenance.
Ultra violet light degrades some finishes as does exposure to weather and water.
Some softer woods will rot or deteriorate faster than hardwoods. White Oak is a very durable wood for doors as is Mahogany and Cypress.

My front door needed some refinishing:
 

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When refinishing anything wood, chemically stripping the finish off is a must. Part of the finish is embedded in the fibers of the wood and if that isn't removed too the door is likely to stain blotchy because the wood is still sealed with the old finish. Having said that though it's difficult for the DIY to strip the finish since the government has banned to the public the chemical which makes removers work. You might be better off in the long run finding a professional to refinish the door for you. The professional can still get removers that works.

Very likely the finish is a spar varnish. Except for some professional coatings polyurethane is an interior finish and you shouldn't use it when going back with the new finish. For an exterior door you need a finish that is elastic enough to expand and contract with the wood exposed to the extreme weather conditions and a spar varnish is what is commonly used. The best is Epifanes. It's not available near me. I've had pretty good luck with Cabot spar varnish.
 

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Discussion Starter · #6 ·
About 10-12 months ago I sanded off as much of the previous old oxidizing polyurethane as I could but could not get all of it off particularly off the uneven molding creases, then coated the door with Epifanes (which I think is some form of polyurethane but don't know for sure). The finish you see on the pic above is that finish about 10-12 months later. I think it did not do well because of residual underlying previous polyurethane coats that I had sanded off but residual remained in the grain. So I am out of varnish/polyurethane/Epithanes options and am now thinking of either painting the door with solid color acrylic/latex exterior paint (any thoughts?) or replacing the door/frame/etc with a fiberglass or acrylic material door. All comments are welcome.
 

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I’ve used these with PSA abrasives:

Rockler Contour Sanding Grips

They appear to be NOS attachments for the discontinued Porter Cable 444 profile sander which I’ve often used until picking up a Festool LS-130 profile sander which is just okay but not great for removing finish on contours of different shapes.
 
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