Weaving is the process of interlacing two sets of yarn to make fabric. Those two sets are: Warp yarns and Weft yarns. Because warp and weft yarns do different jobs, they don’t need to have the same qualities. Warp yarns must be tough: low stretch, strong, stable, and able to resist rubbing. Weft yarns mainly need to flow smoothly from the shuttle and give you the color, texture, and feel you want in the finished cloth. In this article I will explain warp and weft yarn characteristics in weaving and also comparison between warp and weft yarn in weaving. 
Warp Yarn Characteristics
From an architectural point of view, warp yarn must withstand the rigors of weaving with little damage or change. Four qualities make a good warp yarn—inelasticity, integrity, size, and abrasion resistance.
1. Inelasticity:
A yarn that’s appropriate for a warp yarn will hardly stretch when pulled and bent over your finger, and it will show little change in size. This is a good thing. Warp yarn goes on the loom under tension and is woven under tension. For the cloth to have consistent density, the tension should be the same across the width and length of the cloth. Inelastic yarn is easier to put on the loom with reasonable consistency, and easier to weave off.
2. Integrity:
Warp yarns, singles or plied, should be spun firmly so they won’t drift apart under tension. They must endure changing tensions as the shed opens and closes, which exerts a “tug and release” on each strand of yarn every time a new shed is opened or a treadle is tromped. If the yarn has no integrity, it will lengthen a bit with each tug. A warp yarn not held under the same tension as its neighbors will droop into the open shed and become abraded, snagged, and ultimately torn by the passing shuttle. The only way to manage this situation is to replace the drifty warp end.
3. Size:
A warp yarn needs to be of a size that will fit through the reed and heddle eyes. Reeds come in different spacings from four to fifty (or more) dents per inch (2.5 cm). This range makes it possible to weave from thick to fine yarns. With an assortment of reeds, you can weave a wide range of yarn sizes. Heddles are available in standard and large-eyed types, so if you want to weave with thick yarn, you’ll want to use ones with large eyes. It’s important to note that if you want a flat cloth, then you’ll want to use yarns with the same grist and twist. Thick yarns combined with thin, or soft-spun yarns combined with firm crêpe yarns will produce a highly textured cloth.
4. Abrasion Resistance:
The structure and surface of a warp yarn needs to resist abrasion in the reed. Any hairiness will tend to increase with each pass of the reed and eventually raise a nap on the yarn. As the nap grows longer, fibers can come off the yarn and form “doughnuts” around the reed blade. This obstructs the yarn’s passage through the reed and hastens its failure.
The natural characteristics of flax, hemp, and cotton make them perfect for weaving. The yarns are inelastic. The fibers are readily spun into fine yarns that are, by nature, extremely strong. Fine cotton is adequately abrasion resistant, and linen and hemp are supremely so. Voilà!
Weft Yarn Characteristics
Weft yarns don’t need to be stretched on a loom, rubbed by a reed or beater, or pulled up and down while weaving. The demands placed on them are simple. To wit: weft yarns need to feed easily off the shuttle, be it a stick, ski, boat, or end-feed style. Although it’s possible to pass weft yarn without using a shuttle, it’s precious slow work. If your yarn won’t behave coming off the shuttle, then set the twist, size the yarn, take greater care winding the shuttle, choose another shuttle, or choose a different weft yarn. Do something, because weaving without a shuttle is on par with sweeping the floor with a clothes brush. It can be done, but why?
Comparison between Warp and Weft Yarn in Weaving
| Feature | Warp Yarn | Weft Yarn |
| Position in fabric | Lengthwise (on the loom) | Crosswise (inserted with shuttle) |
| Tension | High, constant | Low, only during insertion |
| Main needs | Strong, stable, abrasion-resistant | Feeds smoothly, suits fabric look |
| Stretch allowed | Very little | Some stretch is okay |
| Texture | Usually smoother, firmer | Can be softer or more textured |
| Variety | More limited | Much more freedom |
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Conclusion
Warp and weft yarn each have their own job, and that’s why they need different qualities. Warp yarn is like the backbone of the fabric – it must be strong, firm, and able to handle a lot of tension and rubbing on the loom. Weft yarn is more relaxed – it just needs to come off the shuttle smoothly and help give the fabric its color, texture, and feel.
