If you are a reasonably talented fellow when it comes to woodworking, I would seriously consider replacing the doors. Slab doors are fairly inexpensive and come already pre-primed. Mortising hinges and setting door set holes is not that difficult, especially when you have the original to use as the template.

The main advantage is that you will totally eliminate the heavy oak graining and get superior paint adhesion to going over old varnish.

I have luan slab doors and that isn't nearly enough to hide the grain. Add a filler then sand down between the prime coats maybe? I didn't want to hide the grain so it's fine by me.

I do suggest using a paint conditioner like Floetrol for the finish coats to eliminate brush strokes.

Use a "grain filler" or "pore filler" prior to priming. Solvent-based fillers are easier to work with, but messier. Water-based fillers are easier to clean but set up really fast. Work on a 2 ft section at a time. I've heard this product is good: https://www.amazon.com/CrystaLac-Wood-Grain-Filler-Quart/dp/B001DT3LN0

I have used Mohawk grain filler on furniture, but it is solvent-based.

One application is probably good enough. Do a sample piece, then prime and paint to make sure you are happy with the appearance.

How many doors are you doing? I would take them outside to do the sanding and grain filler.

12 of various sizes

Cool. Set them on sawhorses and then stand them up vertically to dry. A squeegee/spreader for spreading Bondo is good. A basic electric sander will help you speed things up. The sanding should go quick. The idea is to cover all of the pores but not let material on the surface to harden.

You are probably looking at a 4-6 hr. job.

Good Luck!

David Jensen,

Which brand and name of said primer would fit the bill?

I just did 13 of these a couple months ago. 2 coats of 123 and 3 coats of Behr Ultra semi-gloss. The grain is very prominent. I wanted to replace the doors but the people I was helping wanted to save money.

Carlos's process might work. But it sounds messy and a lot of work.

Good luck.

Thanks for the feedback jn3344. I was thinking of using 2 coats of zinsser 123 plus and the coats of paint. Good to know what my expectations should be if I go that route.

123 is water based. In general, the oil based primers do a better job of lessening the prominent gain because they sand much better, leaving the grain filled as the surface is sanded away. Oil primers readily sand, dusting up and not clogging the sandpaper. All the major manufacturer's have a version of high build oil enamel undercoaters.

True grain fillers are only spread on bare wood. They are a heavy paste which is spread on, hardens, and then can be sanded smooth. This was traditionally done with new oak doors where heavy grain was not desired. The filled grain would still take stain. Sometimes the paste was removed with "excelsior", which is a kind of shreded wood that looks a little like steel wool. This is a very labor intensive process which I last did with my father in 1958!

No need for more than 1 coat of primer.

Just accept the grain??

i do have a tendency to sand thru. Thoughts on how to handle that? Especially at edges. I do try to sand lightly.

Since you have so many doors why not experiment to see if the grain is acceptable. Remember it shows up when light hits at an angle so if you don't see much in the way of bright spots now you won't see much when painted. Lower gloss shows fewer bright spots too. I repainted the kitchen with satin and I think the oak grain is somewhat less noticeable now. I like the grain though. It gives the eye something to see rather than scan to find imperfections on that enormous plain surface.

It was enormously restful painting out my luan doors. I didn't realize how depressing or dominating the dark slabs were in my little house.

If you use a palm sander it's hard to sand through. It's when I am hand sanding I put pressure on spots I think need more and then get into trouble. Hope your doors are better quality than my luan doors, the skins are thin and flexible and if I really went to town I could outline the frame under the skin.

Kathy Yata,

Thats very helpful thank you. What kind of primer and paint did you use?

I tried BM Fresh Start enamel underbody (217) but it took a week before it wouldn't ball up sanding. At 24 hours it wouldn't powder. And it still scratches off easily.

On my veneer I can see the seams already in places before priming/painting so I'm concerned about that. Some are lifted ever so slightly.

You shouldn't need to do much sanding after you initially sand them prior to priming.