Silk fabrics require special care to ensure that the fabric does not bleed, shrink, lose its sheen, or tear. If you want to wash silk, make sure to do it carefully to ensure the integrity of the fabric, and be aware that in the case of fabrics marked “dry clean only,” it can be dangerous to hand wash. Dry clean only fabrics may bleed, stain, or shrink significantly if they are washed by hand.
Before you wash silk, it is a good idea to do a spot test first to see if the dye bleeds. Spot test with a cotton ball or soft cloth dipped in cool water and a mild detergent, and pick an area of the garment which is not visible. Gently blot the fabric, allow it to rest a moment, and then blot again with a clean, damp cotton ball or corner of the cloth. If the clean blotter comes away stained with dye, the fabric should be dry cleaned. Likewise, if the fabric appears to have lost its sheen, you may want to dry clean it.
To wash silk, start by shaking the fabric and lightly brushing it to remove surface dirt. Then, soak it for two to three minutes in cool water with a gentle soap. Do not use detergent, which can make the silk shrink. Swirl it in the soaking water, and gently blot any areas of the garment which are stained. If serious stains are present, use a stain treatment which is labeled for use on silk before the soaking process to loosen the stains so that you can remove them.
Rinse the silk in several changes of cool water to remove the soap. If you want to ensure that all of the soap is removed, add a glug of plain white vinegar to the rinse water to encourage the soap to precipitate out, and rinse again with plain water before preparing the silk for drying. Once the garment has been rinsed, lay it out on a thick towel and roll the towel up to absorb water. Do not wring the silk, as this will wrinkle and tear the fibers.
After you have rolled the silk in the towel, unroll it and lay it out on a flat space to dry, ideally with a fresh towel underneath to soak up water. Keep the silk out of the sun, as sunlight can damage the fibers, and avoid exposing the fabric to heat. If you want to speed the drying process along, you can use an iron on a cool setting to iron the reverse side of the fabric.
Some silks are safe to run through the washing machine. To wash silk in a machine, use a very mild soap safe for silk, a short cycle, and the “delicates” setting. It is also a good idea to put silk into a lingerie bag or pillowcase for washing so that it is not damaged by the washing machine's agitator. Do not run silk through a dryer, as this can cause it to shrink.
Although washing silk sounds like a lot of work, this fiber is very durable, and it will endure for years if well cared-for. It is a good idea to wash silk regularly so that it never has a chance to become soiled or stained, rather than to save washing for garments which have gotten dirty, as it can be hard to lift embedded stains.