This is the final part of a series that begins with Blocking Notes (Intro).
Caring for handknits involves a few simple rules. One of the most important is to never hang a hand-knitted garment. It will stretch, and may not bounce back after washing. Fold the garment (don't fold the same way every time to avoid making creases permanent) or roll (particularly for delicate or heirloom articles such as christening shawls). Don't place heavy articles on top of handknits.
Wash garments carefully and gently. Use lukewarm water to be safe with woolen fibres that may full (the words “full” and “felt” are often used interchangeably, although technically what happens to a woolen article that is washed in hot water with lots of agitation is called fulling), although you can use hot water (this may be necessary if the article is very dirty) as long as you don't agitate the article. Superwash wools don't full*, and can usually be machine washed on a gentle cycle. Don't machine-wash other yarns unless the ball band says the yarn is machine-washable. If you have a gentle cycle on your washing machine, and want to machine wash an article where the ball band says to hand wash, try it out on a swatch first. If you do use a machine, put the article in a laundry washing bag first to help minimize pilling and stretching. Use a gentle detergent, hair shampoo, or a specialized wool wash. I always rinse the article, even with those wool washes that claim to not need rinsing, as the detergent tends to build up over time, although some people claim the wool wash residue helps to deter clothes moths.
After washing, squeeze out all the water, roll the article in a towel to remove more water, and then dry the article flat on another dry towel or a drying rack, shaping it gently. You can also use a wooly board, but will probably have to wet the ribbing after the article has dried and let it dry off the board to ensure it's springy.
Cotton tends to get mouldy so make sure it can dry quickly when you wash it, and that it's completely dry before putting it away.
Don't machine dry the article unless the ball band says it's possible. If you do use a machine, don't overdry the article; removing it when still slightly damp helps it keep its shape.
Most handknits don't need drycleaning, although some rayon yarns benefit from it [PARK, p 233].
Food stains tend to set if left, so make sure handknits are kept clean.
Often handknits will lose their shape after being worn for a while since they tend to lengthen due to gravity. Washing and blocking generally brings the shape back, although with yarns that have little or no memory, such as cotton, it may not be completely effective. To take this into account when knitting the garment, a lot of people recommend knitting a gauge swatch, washing it the way the garment will be washed, then hanging it when dry with weights to simulate gravity. This way you can tell how the yarn will react when it's worn. You may wish to make the article with a slightly tighter gauge, more seams, or more structure, all of which help counteract the tendency to stretch.
One big problem when storing woolen items, whether handknits or other items made of wool (including wool blends), is with moths. You know you have a moth problem when your woolen items have irregular holes in them. In my experience, the expensive yarns such as cashmere are particularly singled out for attack. There are two types of clothing moths whose larvae eat wool, particularly if the wool was stored without being properly cleaned. They will also eat wool that is still unspun or in skeins. To prevent infestation, wash every woolen item before storage, or store the unknitted yarn in ziplock bags, airtight bins, or zippered cotton pillowcases. Clean closets frequently by vacuuming. You can keep clean items in airtight containers, making sure they're thoroughly dry first. You can freeze items for several days at temperatures lower than -18 °F or -28 °C, or hang them in sunlight and brush thoroughly. If you do find an infestation, clean the item by washing or drycleaning. More information is in [RUST].
*Well, they're not meant to, anyway.