It really depends on the fabric of the dress, and how you managed to shrink the fabric. The easiest fabrics to restore are chiffons, usually rayon or silk, which are very sheer and light. Then, the next easiest fabrics are knit natural fabrics, cottons, rayons, and silks. I personally have never been able to restore a wool, spandex, or synthetic garment that has shrunk drastically to its normal size. Hand washing related shrinkage is generally reversible, as is contraction related to cold water machine washing. However, any amount of tumble drying can permanently shrink the fabric. If you still think there is hope, then buy a fabric steamer (a Conair model sells for $30) and gently tug at the hem while the dress is being steamed. This method has been able to restore washed rayons labelled dry clean to their original size. However, anything that has remained shrunken for a period of time tends to shorten if the original width is too tight for the body. So fitted dresses or those cut on the bias will tend to shrink back slightly while wearing.
Michelle Tsien, April 2008
