Yarns are made up of a wide variety of materials, ranging from synthetics such as acrylic, rayon, and nylon, to natural fibers including various wools, cottons, and silks. Plus, you can find numerous combinations or blends of any materials.
When choosing a yarn for a project, you should take into consideration how you will use the piece when it's completed. If you're making a baby blanket, choose a yarn that will stand up to repeated washings, not something the new mother will have to handwash and lay flat to dry. If you're making a tablecloth or bedspread that will someday be an heirloom piece, invest in good quality cotton that will withstand the test of time through several generations without falling apart. For a nice warm sweater, you can't beat wool. Its inherent qualities still make it the best bet for durability and warmth. After all, Mother Nature does know best!
Wool
Of all the natural fibers used to make yarn, wool has been, and remains, the most popular choice to work with when creating a piece that you want to endure for years to come. Spun from the fleece of sheep, its resilient nature allows the stitches to retain their shapes. Wool is soft, easy to work with, and relatively lightweight. It's available in many different size yarns, from fingering weight to bulky. You can crochet with wool to make everything from beautiful, warm weather sweaters to cozy, wintertime pullovers, hats, scarves, mittens, socks, and Afghans. Due to advances in the manufacturing process, wool has become more low maintenance as well. But be careful to read the yarn label for specific washing instructions.
Wool is gathered from various breeds of sheep, each providing its own unique texture. Other animals are also painlessly sheared to give you more luxurious yarns. Goats supply fuzzy mohair and cashmere. Alpaca and other members of the llama family give you a wonderful selection of soft wools, and the Angora rabbit provides that exceptionally delicate, fluffy, and familiar yarn.
If you're one of the many people who's allergic to wool, don't despair. Many new synthetics emulate the real stuff, and if you don't tell, no one will be able to tell the difference.
Silk
Spun from the cocoon of the silk worm, silk yarn has a smooth, oftentimes shiny finish. Lightweight and absorbent, silk yarn is a perfect choice for warm-weather garments. Silk's often combined with cotton or wool to increase its elasticity and durability.
Cotton
Once thought of only as "thread," and mainly used to make doilies, bedspreads, and tablecloths, cotton has become known as a versatile yarn. It's available in a wide range of sizes, from very fine threads to worsted weight yarn. For the same reason that we love to purchase clothes made from cotton, garments crocheted from cotton can give you the same wonderful feel. Cotton yarn is also a good choice when making home decor items, such as placemats, potholders, curtains, and doilies. It's washable, durable, and readily available.
Synthetics
This family of yarn is produced from man-made fibers and includes materials such as acrylic, rayon, nylon, and polyester. Designed to look like the natural fiber yarns, they're readily available in a wide range of sizes, colors, and textures and are generally less expensive than their natural counterparts. These yarns, especially those made from acrylic, are good for making items such as Afghans and baby blankets because they require little care. But be sure to check the label for instructions. Synthetic yarns are quite often used in combination with natural fibers, which have significantly expanded the yarn industry's ability to provide us with ever-new textures, colors, and qualities of yarn to crochet with.
Novelty yarns
Novelty yarns are fun and funky and can add plenty of interest to your work without having to incorporate complicated stitch patterns. From eyelash yarn with many soft, fringy lengths attached to a fine strand of yarn to velvety chenille, bumpy boucle, glittering metallics, and slinky ribbon — any of these yarns, used alone or in conjunction with regular yarn, add a fresh and fashionable look to any piece that you create.
Other materials
If you're really feeling adventurous, you can crochet with any material that resembles a string. You can use fine, colored wire and hemp to crochet cool jewelry, nylon cord for waterproof bags, and outdoor seat cushions, and even embroidery floss and sewing thread to create appliqués and accents resembling an intricately woven tapestry.