Wood absorbs and releases moisture. The ONLY thing that you can do to keep it from doing that is to keep humidity levels consistent, around 30-40%. If you can't do that, then your wood WILL expand when it absorbs moistue, and shrink when it gets drier. Like the seasonal changes between a more humid summer environment and a drier winter one.

That is NORMAL behavior for wood.

When wood has a film forming coating applied, that seasonal movement will cause separation of that coating wherever pieces are joined. ''Cracking'' if you will. The movement between the cross grains, like on a mitered joint, is more than movement of cross and long grain, like a stick and cope door. Paint will show this much more than a clear coated wood, because there are those solids in the coating.

If you cannot deal with the minimal NORMAL joint lines in painted cabinetry, then don't get wood doors. Despite the extreme wood prejudice that the uninformed have, there is nothing wrong with choosing MDF or HDF for painted case goods. It has much better cross dimensional stability ecause of the different orientations of the cross linked wood fibers. I wouldn't choose a single piece routed door, but a true 5 pc door is more than acceptable. You won't get those join lines telegraphing through the paint.

Those are your three choices: install a high quality humidity control system in your home, or get over seeing the normal join lines, or choose MDF.

And don't do mitered doors in paint no matter what.

Holly springs:

Thank you for your reply. "Minimal" join lines I might be able to deal with...the real issue for me is what is minimal and what it looks like.

The popularity of painted cabinets has not influenced my area too much. No one I know has used them in either new home construction or remodeling. The only place I can see them is at the custom cabinet shop; I wonder how good his humidity control is in the showroom and what his sample cabinetry is made of. When I return the door samples, I will be looking at the sample with "eagle" eyes.

Painted cabinets seemed like the perfect solution to my husband's concept of wood and "matchy-matchy." Our 1980 home originally had a gorgeous, hickory stain on red oak that was not the rage in 1980. It has NOT "aged-well." The polyurethane has yellowed and the oak reddened; that equals orange to my eye. He thinks the new cabinets have to match the old trim because we will see the kitchen due to an opened wall from the living room; I am reluctant to spend thousands of dollars to replace wood cabinets with the same color and wood I do not like. Select/ hand-sorted hickory looks fine as does plain or rift sawn white oak...but THAT color!!! I see orangey-red in my house when I prefer a rich brown tinge.

Jakuvall:

Thanks for the tip...is cracking the reason why?

Mitered doors will open at the joint more than rail and stile and is is not even. Wood will move 6xs as muck across the grain than it will with. So there is vastly more movement at the wider part of the miter. I would not count on any humidity control except maybe NASA's for that.
I will not sell a painted miter.

Jakuval:

Thank you so much for that info; I have lurked here for over a year and have not run across that information.

I have doors home for sample colors; one of the painted samples is mitered. The KD did not mention anything about paint and mitered doors; I honestly do not remember if the door style we picked is mitered or not since it was so long ago. I will definitely check that detail before I place the final order.