If it is clean, the embroidery should be placed face down on a padded white surface, covered with a quite damp white cloth, such as a man’s handkerchief, and pressed well with an iron. After pressing, it should be beautiful, the fulfillment of hours of careful stitching.
If laundering is required, first soak the embroidery in cold water and vinegar for a half hour,* then wash it in lukewarm water with Ivory Snow. Rinse several times. Roll it in a white towel to press out excess moisture. Immediately unroll and lay the embroidery face down on a padded white surface. Cover with a dry pressing cloth and press well. Be sure the embroidery is thoroughly dry before mounting.
Once upon a time cotton embroidery floss was runproof, even boilproof, but no longer. Because of laws protecting the ecology, all yarns, including needlework yarns, have reverted to less stringent levels of colorfastness. There is no cause for alarm, though, as “bleeding” occurs rarely. Should excess dye bleed, simply flush it out with repeated rinsing.
This tip is an excerpt from "Bk54 Linen Stitches".