Some silks should be dry cleaned (notably Dupioni) but most can be handwashed, especially if you wash the fabric before sewing. Dry cleaning gets more expensive every day, and the smell of perc (the dry cleaning fluid) in our clothes is not our favorite fragrance. And worst of all, silk begins to look dingy and dull after just a few trips to the dry cleaners. Many silks look better and last longer when hand washed.
But beware, many inexpensive and poorly woven silks may fade, become stiff, change texture or lose their sheen when hand washed. Try a test piece in a series of launderings before spending a lot of time and effort in any project.
Silk Noil MAY shrink noticeably in handwashing (how much depends on the weave), and should absolutely be pre-shrunk before being sewn up to minimize shrinkage in the final garment. Silk Noil may be machine dried, but this will increase shrinkage and should definitely be done before being cut and sewn.
Silk Dupioni can be handwashed, and launders beautifully; however, it changes the texture and sheen of the fabric. Hand wash a small scrap or swatch and check to see if you like the way it looks. We wash all our dupioni that is custom dyed, and it has a much softer texture, very different than the crisp finish it has off the bolt.
When hand washing a ready-to-wear silk garment, make a wash test on an inconspicuous part of the garment, the inside back of a hem, for example. Nothing in this document should be considered a recommendation or guarantee of success.
Here's how it has worked for us;
Silk Crepe, Noil, 2 ply silk and dupioni shrink the most and should be pre-shrunk before sewing up. Place the silk in a sink or tub full of lukewarm water and mild soap. We like Ivory Snow (powder), some people swear by Woolite, some people like Orvus Quilt Soap (available at some Quilt stores as well as many Equestrian Saddle and Tack shops!) and some even use their favorite shampoo. Whatever you use, follow the package directions. Rub the silk fabric for a few minutes in the soapy solution and drain. Rinse in clear, cool water until all the soap is gone (don't wring, silk becomes weaker when wet!). Fold the garment flat and roll up in a towel (like a cinnamon roll) to remove excess water overnight. Remove from the towel and iron dry with a medium-low setting.
You can dry silk Noil in the dryer, but it shrinks more.
Routine hand washing
Soak the garment in lukewarm water and a mild soap solution (see pre-shrinking, above). Rinse in clear, cool water until all the soap is gone. then fill the sink again and add a quarter cup of white vinegar to the final rinse. Vinegar neutralizes any remaining soap, and allows it to rinse out completely restoring the fabric's natural sheen, it can make a dramatic difference. Give the fabric a final rinse in clear, cool water to remove the vinegar smell. Roll up in a towel to remove moisture, then dry flat on a towel or on a padded hanger. Iron with a low-medium temp iron while still slightly damp.
Why Silk shrinks
Silk fiber is a protein, like your hair, and it does not itself shrink. The way the individual fibers are twisted together when weaving is what causes silk to shrink. Highly twisted yarns and loose weaves cause shrinking when water releases twisting energy in the fibers. It's a bit like twisting a rubber band then reducing the length, seeing it bunch up. Silk bunches up the same way. Ready to wear silk garments shrink because manufacturers don't go to the trouble of washing the fabric first. Imagine that.
Silk Fabric Care: Handwashing Silks-Silk Fabric Care: Handwashing Silks