From information that I found, it seems that silk is dry clean only (most of the time anyway) simply because the garment manufacturing company was too lazy to pre-wash it before they made the garments, and if you wash it after the garment is made, it’ll shrink. But if you pre-wash it, it’ll be fine.
Or something like that.
Sometimes, the silk is too fragile or the colors will run too easily to wash, and then it should be either handwashed or drycleaned. Eh. I don’t want dryclean only silk.
The fumes, Boss, the fumes!
Good information is important to have. :p
I’ve also read that silk shrinks at least 10%, so buy enough to cover the shrinkage.
And as I search further, I find this information supported elsewhere.
Lined garments are just about never washable, and silk garments whose silk was not prewashed before sewing are often not washable. I have never heard of an off-the-rack lined silk dress that was not marked "dry clean only." And of course, truly dry-clean-only garments are NEVER dyeable. All forms of dyeing require washing.
The way to make a silk dress washable is to prewash the material before sewing it into the dress. A silk dress, especially a lined one, should be assumed to have missed this incredibly simple and easy step, and to be dry-clean-only. When you wash a lined garment that was marked "dry clean only", either the outside layer of the garment will shrink, or the lining will, but they will never match each other. The way the lining fits under the outer layer will almost inevitably be completely ruined.
In contrast, if you prewash and dye some nice silk chiffon, then have it sewn together (there are thousands of tailors who can do the sewing for you!), the dress is washable. If the fabric, or its trim, is too fragile for machine washing, it should still be hand-washable.