How to smooth old doors for paint

5 years ago

Hi - total beginner here. The previous owner left behind these already painted or primed plain bifold closet doors with (I think?) veneer surface. They have lots of little bumps and some wood grain. I'm trying to get the surface as smooth as possible to paint with SW Agreeable Grey in satin and add some modern square bar pulls. On thrse particular doors (I have a bazillion I'll be doing) the wood grain isn't so pronounced, but there are some little long lines. Should I fill those with Aquacoat white cabinet wood grain filler...?

And the builder issue is how visible the bumps really are. What I've tried so far with these doors and another sample old door elsewhere:

- I sanded the doors with 220 then a bit of 100 and an orbital sander (I don't have any grit between those on hand) and managed to achieve some smooth areas but other areas just remained bumpy - did I go too far with sanding or not far enough? Should I try to continue sanding without going all the way through the veneer?

- On these planks, I used a 3/8 nap. Is my nap making it worse? Would a second coat of the SW grey and/or a different nap smooth it out? Is my random technique of rolling roller upwards and downwards the problem? Should it just go one direction?

- On some scrap wood I tried Rustoleum filler primer (an auto spray primer.). While it smoothed out bumps, it was a smelly, messy job and the first coat of the SW paint over the top had a metallic sheen. Should I just use the Rustoleum primer, then cover with another regular white primer then the SW grey paint? Is there another high-build primer (preferably white) I should try?

I'm very confused at this point. (Also, yes, I'll wait for the wood filler to dry then sand and wipe dust before painting those areas and I'll likely hit any bare stripped-back areas with a bit of white primer before painting. And the edges of the door look raised/ridged and need more sanding, yes?

Basically, how smooth is it feasible to get this door and what's the least painful way to do it? Thank you for any pointers.

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Comments (5)

cat_ky
5 years ago
last modified: 5 years ago
I would strip them, and then light sand them. What you are seeing is roller stipple. You may cause damage to the doors, before you ever get that smooth enough, if sanding because, it takes a lot of sanding to get rid of that.
rwiegand
5 years ago
You probably need to invest in a better sander and good sandpaper. Something like a 6" Rotex will take it off pretty quickly (at a significant price), but at least a 6" random orbit sander with a 5 mm orbit and ability to connect it to a vacuum cleaner. (both because you don't want to breathe that stuff and the sanding goes a lot faster if you suck away the dust). Start at 80 grit, then 120, then 180, then 240 (or similar, depending on what you find). Don't ever skip grits, you'll leave sanding swirls behind. For paint that will be plenty fine. Always remember, use your sandpaper as if someone else is paying for it.
Alley Cat thanked rwiegand
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Alley Cat
Original Author
5 years ago
Thank you! I didn't know how important it was not to skip grits.
rwiegand
5 years ago
You can skip, but it takes forever to eliminate 80 grit scratches with 240 paper, and almost no one has the patience to do it. Stepping through the grits in order is much faster in the end. Generally the finer grits go quite quickly once you have a uniform surface from the coarsest grit. Experiment to see where you need to start-- you might be able to start at 120 if it's just paint stippling. When your paper loads up you need to switch to a new sheet.
cat_ky
5 years ago
Remember those doors are wood veneer and its very thin. If you sand through the veneer, you will never have nice looking doors. Best to do the stripping and then a much lighter sanding, even by hand.