Self patterning yarn is yarn that creates a specific pattern when used to make an intended item. Typically, this kind of yarn is used for knitting, but it can also be made for crochet projects or other yarn crafts. This kind of yarn can create simple patterns, such as stripes, or make more complex ones that look like fair isle or intarsia knitting. The main benefit of self patterning yarn is that it can recreate these looks without the difficult techniques normally required of the knitter, and without any of the weaknesses of items made with these techniques. For instance, the wrong side of an item made with self patterning yarn will be entirely smooth, just like an item made out of any other single yarn, whereas fair isle and intarsia both leave loops of yarn on the wrong side of the item.
The design of self patterning yarn is actually relatively difficult. When the yarn is dyed, it must match up with the intended pattern and tension perfectly. It is relatively easy to create striping yarn by measuring how much yarn goes into each row, but it can be difficult to create shapes and vertical stripes with much accuracy. For this reason, the pattern that appears when using this kind of yarn is usually at least partially based on horizontal stripes created by several rows in a single color.
When knitting with self patterning yarn, it is important to plan the project around the qualities of the yarn. For instance, with striping yarn, the stripes might appear in a thin scarf but not a wide one. Alternately, perhaps the color will change in an inconvenient place in the final item. Once the initial planning is completed, though, the rest of the project requires only sticking with appropriate tension in order to achieve the desired pattern. Many people ignore the planning step entirely and let whatever unique designs come out of their project be a surprise.
One of the most popular uses of self patterning yarn is in the construction of knitted socks. These items benefit particularly from the use of self patterning yarn because there are no loops on the inside of the socks to catch one’s toes, and the socks can be thinner. Socks are so popular for this type of yarn that the majority of self patterning yarns are made at an appropriate weight for socks. Nowadays, more and more yarns are being made at heavier weights for items such as sweaters, and even when an appropriate weight is not available, it is possible to dye the yarn for the perfect patterned item.