What is 2 way stretch and 4 way stretch fabric
It is really easy to understand. Lay a piece of fabric flat on a table. Pull it vertically and horizontally. If the fabric stretches noticeably in both directions, it is 4 way stretch fabric.
If it only has clear stretch in one direction, either vertical or horizontal, while the other direction has little or almost no stretch, it is 2 way stretch fabric.
Whether fabric is 2 way stretch or 4 way stretch only depends on which directions it can stretch. It has nothing to do with how stretchy it is.
For example, one 4 way stretch fabric can stretch to 150% its original length both crosswise and lengthwise. But a 2 way stretch fabric can stretch up to 200% its original length in the stretchable direction. Do not mistake the numbers. The “4” in 4 way stretch and “2” in 2 way stretch only tell you stretch directions. They do not mean 4 way stretch fabric is always more elastic.
What kind of fabrics feature 2 way stretch and 4 way stretch properties
We will explain this separately for woven fabric and knit fabric, in simple terms.
Woven 2 way stretch
To make woven fabric stretch in only one direction, we add elastic yarn to just one direction. The most common type is weft stretch fabric.
Here is an example: The lengthwise warp direction uses regular polyester or nylon yarn with no stretch. Spandex elastic yarn is woven into the widthwise weft direction during production.
The finished fabric can stretch side to side and bounce back once you let go. The vertical lengthwise direction hardly stretches at all, with very low elasticity. We can also make woven fabric with stretch only in the warp direction, but this type is far less common.
Woven 4 way stretch
For woven fabric to stretch in both directions, we blend certain amount of spandex elastic yarns （See the common types of spandex yarn）in both warp and weft directions. There is spandex in the warp and also in the weft. The fabric can stretch and recover when pulled crosswise or lengthwise.
Knit fabric: 2 way stretch and 4 way stretch
4 way stretch Knit fabric（see natudon 4 way stretch fabrics for sportwear)
Most stretch knit fabrics for sportswear on the market are 4 way stretch. By adjusting yarn combinations and loop structure, they stretch and recover crosswise and lengthwise. Yoga wear and tight leggings you normally see are mostly knit 4 way stretch, not woven.
Knit fabric has natural stretch from two factors. First is the loop structure. Knit fabric is made of interlocked yarn loops. These loops can deform and expand when pulled. Even without adding spandex, some knit fabrics have a small natural stretch.
Second is added spandex. When we knit with spandex, the fabric can stretch further and recover much better. Almost all yoga pants ,underwear and compression garments use this kind of knit fabric blended with spandex.
Does 2 way stretch knit fabric exist?
This is a common misunderstanding. Not all 2 way stretch fabrics are woven fabric with spandex. Actually,there exists a great many of 2 way stretch fabrics in the market nowadays.
Warp knit fabric containing spandex can be made into 2 way stretch，too. We just adjust stitch patterns and yarn placement.
Take this patented stitch design from 1977 as an example. A warp knitting machine uses non stretch regular yarn to interlocked loops, forming a course（the illustration of loop and course above）. While knitting each horizontal course, the machine lays spandex elastic yarn along the vertical direction of the loops. The spandex works like a rubber band, trapped inside the loops made of ordinary yarn. The patent creates a special clamping structure to hold the spandex tight and stop it from shifting. This makes a 2 way stretch knit fabric with spandex, instead of the usual 4 way stretch. This is just a simple, easy to understand summary. If you want to study this technology in depth, you can check the knit patent article.
