I have built a few dozen cabinet doors for our kitchen, garage, and
miscellaneous cabinets. Unfortunately, about half of the doors I have built
over the last few years have warped slightly. So two doors that meet in the
middle don't sit flat next to each other anymore. They still work fine, it
just looks "unprofessional".

I like working with regular #2 pine, for the availability, price, and a bit
of a "rustic" appearance. I've used it for cabinets, face frames, drawers,
and drawer fronts. The doors are the only items giving me trouble.

The doors are simple frame and panel contruction. Just a 1/4" groove all
around with a flat panel.

To make the frames, I bought 1x6's and 1x8's, then ripped them into 2" wide
boards. I selectively cut between knots and chose the straightest grained
lumber for the frames.

Most of the doors have solid panels glued up from individual boards, while
other's have plywood panels. I've tried both 1/4" and 1/2" thick panels,
and the warping is about the same with either.

The doors were flat when I finished them, so I know it wasn't a clamping
problem. In fact, they were flat when installed, and only warped after
being on the cabinets a few weeks.

I don't have a moisture meter, but the pine boards were kiln dried when I
bought them, and most have been stored in my dry garage for a year or more.

Anyway, I'm curious why so many of my doors are warping weeks after they
have been installed?

Is it because I only applied finish to the outside, leaving the inside
unfinished?

Is pine just a poor choice for door frames?

More importantly, is there anything I can do to get the doors to sit flat
now that they have warped?

Thanks,

Anthony