zaaephod
I agree with everything said above.
As a furniture maker (as are many others here), properly drying the wood is of paramount importance to how the finished piece will come out.
Some years ago, I built a coffee table with glass inlays. The glass inlays had a 1/16" gap all around the edges and it looks great after 11 years in service. I had a friend that took my plans and built his own copy shortly thereafter. Within a month his exact copy of the table was falling apart at the seams. The reason? Wood shrinkage.
On my table, I made certain the wood was acclimated to the final environment where it be used (indoors, low humidity). He built his from box-store lumber that he never let acclimate and hence, the final result. His table was contracting (still drying) and binding around the glass inlays. Since the glass wouldn't shrink, something had to give (the wood split).
You project warped because the milled side was opened up and exposing a far greater surface area to allow moisture to escape. The back side (unmilled) had far less area and as such, did not shrink as quickly. This resulted in the "bow" or warp.
Trying to force-flatten such a piece usually ends in disaster (it will split on the milled side) since, in effect, you are attempting to "pull apart" the wood fibers on the milled side and compress the fibers on the unmilled side.
Usually there is little you can do to correct this. My suggestion (other than letting the wood dry properly to start with) is to let the finished piece gradually dry. Eventually the unmilled side should match the milled side in moisture content. This will lessen, but not prevent, the warp.
If you absolutely MUST mill a board for a "hurry-up" project before it has a chance to properly dry, run both sides through a planer (or drum sander) to open up the pores, do your milling, sand and IMMEDIATELY put a wood sealer, polyurethane or some other sealing finish on it. This will cause both sides to gradually release moisture at the same rate. It may still warp or bow, but not nearly as bad as "raw" wood.
Just my .02 cents, hope it helps
HFF
