This type of warping is typical of wood used in construction which was not properly dried prior to cutting into working sizes. These 'grids' are called "colonial Bars' and if they are the pop-in type, the manufacturer can easily supply a replacement. If you want to try straightening them yourself, you can soak lightly and let dry under very heavy pressure to hold the wood in exactly the form you want. I use sand bags for this procedure. Allow to sit for at least 24 hours under the weight. Steam will not work for this.
--Previous Message-- : We just bought a home with Anderson windows : with the grids that make it look : cottege-like. We love them, but a couple : of them have warped. Can we soak them and : flatten them or would steaming be better : or are they beyond hope? Thanks for the : help. :