Irene- I would first make sure you love that material and that the shrunken place mat is still big enough to serve it's purpose. If either question is not quite what you wish it was, I would use the material in some other fashion. That being said, I think I would un pick them first, as I would think it would be easier to get the stitch lifted to pick it out, not buried into a crinkled up disaster like described, which could be compounded if the thread also shrunk to a degree also, but if there is trim of lace or ruffle then it may make that decision for you, as I am not sure if the trim could be washed once it was all taken apart and still be reusable to reconstruct the place mat. Then serge or zig zag the edges to keep them from fraying, in the wash & dry process. If the front or back materials did not shrink the same amount you may need to cut down the place mat to even things out. Once they are fully shrunk I would then go ahead and do any embroidery before reconstructing the place mat into a form you like, using a thin layer of batting and a maybe a layer of stabilizer, or medium to heavy weight interfacing the kind that you would use in a waistband or sleeve cuffs as the interfacing will soften but still have some body to it. I think the product being used to stiffen purses would likely be too stiff. Once you had created the top, batting, interfacing, and the backing sandwich I would do quilting lines or stitching to help keep layers together and finally add the bias binding, lace or gathered ruffle around the outer edges. Hopefully it is a material you do love that you had purchased with the intention of adding embroidery to it, as the task of fully remaking them is more of a task than you had intended in having to do. Hope that however you re-purpose these place mats I hope they will be worth your effort and bring you joy when complete. Pam

Perhaps a picture of the one you washed and one not washed would help...a picture is worth 1000 words...also, were they expensive or not so much? Perhaps I would just return them all...

I can only repeat the end of Pams post - will it be worth the effort in the end? Good Luck

Did you make the placemats?
If so did you use iron on stiffening?
I never use iron on interfacing as it can do what you described when washed.
Could be the backing fabric shrunk more or less than the front as well.