Concept of weft knit structures
There are different types of knitted fabrics which we get by applying different knitting structures. Weft-knitted fabrics can be classified into four basic groups by the arrangement of loops in horizontal rows (courses) and vertical columns (wales). All weft-knitted fabrics are based on these four structures.
With a weft knit there is no inter-twining going on between loops, and they only touch at one or two points. This design allows the fabric to stretch, so the fabric stretches in width and length with a little pressure.
Types of weft knitted structures
It has only four types of structure, which are plain, rib, interlock and purl, where plain structure is made using single-bed knitting machine and other three by double-bed knitting machines. The main distinction is how the needles are laid in the two beds to fabricate each kind of structure.
Here’s a breakdown:
Plain Structure:
Composed entirely of face loops or back/reverse loops.
On one side it is smooth, the other side has a lossy texture.
Rib, Interlock, and Purl Structures:
They need both front and back loops to be formed.
Differently from the two machine beds, each structure assembles its needle, that is
a) Rib: Vertical ribs are created by alternating needles on both beds.
b) Interlock : Both beds knit alternatively, and the result is a thicker, more stable fabric.
c) Purl : Knitted face and back loops alternate on needles giving recoil a wavy and reversible texture.
Representation of weft knit structure
Weft-knitted structures can be represented using different methods, depending on the complexity and purpose of the representation. Here are the three main methods for depicting these structures:
A) Loop Diagram
This technique consists of drawing the real loops of the fabric in the way that they actually look.
It is intuitive and also a great way to visualize the interlinking of loops in the fabric structure.
Ideal for basic constructions such as flat knits or simple weft-knitted fabrics.
Advantages
Simple to read and comprehend.
Realistically shows how the fabric gets constructed.
Limitation
- For more complicated structures, such as interlock fabrics, it becomes cumbersome.
B) Notation
Denotes the kinds of stitches with certain symbols:
Cross (×) means it is a single knitted stitch.
Stand in a circle (○): reverse plain stitch (back side of half a stitch)
This blank space is a miss stitch (no loop is created).
Dot (•): A tuck stitch (the yarn is held, not formed into a loop on the needle).
Advantages
Nice way to document and share knitting patterns in a simplified way.
Assists you in quickly identifying the types of stitch.
Limitation
- Hard to make work for something complicated such as interlock knitting which would need to be able to describe two sets of needles working in opposite directions.
C) Yarn-path Diagram
Illustrates the direction of yarn as it moves along the needles while knitting.
A needle is denoted by a straight line along the yarn path
Single jersey: one set of straight lines, one set of needles
Double jersey designs: Two straight lines for the two needle beds
Loop: A piece of yarn wrapped around the needle.
Tuck Stitch: Yarn meets the tip of the needle but does not form a loop
Miss Stitch: Yarn wrapped around the needle but not in contact with it
Advantages
Ideal for representing both simple and complex structures.
A good way to learn exactly how yarn behaves in relation to needles.
Limitation
It Takes more work to render than some other methods.
1. Plain Knit
Plain knit, also known as single jersey, is the simplest and most commonly used weft-knitted fabric. It is created using face loops on one side of the fabric, resulting in a smooth surface on the front and a textured, bumpy surface on the back.
This lightweight, soft, and breathable fabric is produced on single-bed knitting machines and is known for its excellent widthwise stretchability. However, it tends to curl at the edges due to its single-layered structure.
Plain knit fabrics are widely used in T-shirts, vests, undergarments, and casual wear, making them a versatile choice for everyday apparel.
Identification of the plain knit structure fabric
Plain knit structure (single jersey) is the simplest of knitted structures and can be recognized as it exhibits the following characteristics:
1.Fabric Appearance
Front Side (Face):
- The feeling surface is smooth and consists of the sequence of V-shaped loops positioned in columns vertically (wales).
Back Side (Reverse):
- The back is somewhat bumpy, with semi-circular loops creating texture.
2.Edges
The edges of the fabric can be prone to curling:
Front to back along the length (selvage).
From front to back along the long side (hem line).
3.Stretchability
Very stretchy in the transverse measure (horizontal direction).
Not as stretchy along the length (vertical direction).
Extremely stretchable in the width (crosswise) direction.
Lower elongation in the longitudinal direction (vertical direction)
4.Fabric Structure
Only face loops or only back loops but not both
Made on a one bed knitting machine.
5.Applications
Light, soft, and breathable, the fabric is widely used in t-shirts, innerwear, and casual clothing.
6. Notation of plain knit structure
7.End use
Plain knit structures are commonly used for basic T-shirts (for both men and women), undergarments, men’s vests, ladies’ hosiery, and fully fashioned knitwear.
2.Rib knit
Rib fabric is another class of weft-knitted Fabric characterized by alternating face and back loops in the same course, which creates good vertical ridges or ribs. The ribbed property is created through achieved through double-bed knitting machines, every time both needle beds work to alternate (towards each other and away from each other).
Rib fabrics — A type of knit that has horizontal ridges created from alternating knit and purl stitches, rib fabrics have a lot of elasticity in both directions, but they do stretch the most widthwise, making them perfect for stretchy and fitted clothing. For example, rib fabrics do not roll at the edges like plain knit fabrics, so they can be used where stability is desired (cuffs, collars, and waistbands).
Rib structure fabrics can be identified by the following characteristics
1. Fabric Appearance
Front and Back:
Both sides look identical with vertical ridges (raised lines) created by alternating face and back loops in the same course.
The ridges give the fabric a structured, textured appearance.
2. Elasticity
Rib fabrics are highly elastic, especially in the width (horizontal direction).
They do not curl at the edges, unlike plain knit fabrics.
3. Fabric Structure
Made of both face and back loops.
Constructed on double-bed knitting machines, where needles are alternately positioned on each bed.
Common configurations include 1×1 rib (one face loop, one back loop) and 2×2 rib (two face loops, two back loops).
4. Touch and Feel
- Rib fabrics feel thicker and firmer compared to plain knit.
5. Applications
- Commonly used for cuffs, collars, waistbands, and stretchable garments like socks, sweaters, and sportswear.
6. End Uses
Rib fabric is suitable for collars, handcuffs, waistbands, warm outerwear, underwear, socks, swimwear and special types of trims for use with other knit or woven fabrics.
3.Purl knit
Purl knit fabric is similar to the weft-knitted structure, and it features the identical appearance on both sides with a wavvy surface. Worked in alternating rows of face and back loops, this structure yields completely reversible fabric. Purl knits are also thicker and stretchier than plain knits or rib knits and can stretch both horizontally and vertically.
Purl knit fabrics have unique properties that attribute to a cozy and stretchable shine over sweaters, baby-wear, and scarves at the same time.
Purl knit structure fabrics can be identified by the following characteristics
1. Front and Back:
The double-faced fabric has the same look on both sides, featuring a somewhat textured, wavy surface.
Reversible: The fabric consists of rows of face loops and runs of back loops.
2. Elasticity
Purl knits are extensible both vertically (in the direction of the lengths) and horizontally (in the direction of the widths)
3.Fabric Structure
Worked in alternating rows in both the face loops and the back loops.
It is produced on double-bed knitting machines, which alternates needles between the two beds to create the wavey texture.
4.Thickness and Weight
- Purl fabrics are generally thicker and heavier (more dense) than plain and rib knit fabrics due to their loop configuration.
5.Applications
- Usually employed for jumpers, babywear, scarves, and garments based on warmth and maneuverability.
6. Notation of purl knit structure
7. End use
- Purl structures are uses for—Children’s clothing, knitwear, thick and heavy outerwear etc.
4.Interlock knit
Interlock fabric is a type of weft-knitted fabric known for its smooth, dense, and uniform texture on both sides. It is formed by interconnecting two ribbed structures, creating a double-layered fabric with enhanced thickness, durability, and stability.
Produced on double-bed knitting machines, interlock fabric combines the benefits of rib and plain knit fabrics, offering good stretch, shape retention, and a firm structure. Its soft feel and clean finish make it an ideal choice for activewear, sportswear, and premium garments that require both comfort and strength.
Interlock structures fabric can be identified by the following characteristics
1. Fabric Appearance
Front and Back:
Both sides of the fabric appear smooth and identical, resembling a double-layered plain knit.
No ridges or bumps are visible, giving it a clean, flat look.
2. Elasticity
Interlock fabric has moderate elasticity, similar to rib fabric but slightly less stretchable.
The fabric stretches evenly and maintains its shape well.
3. Fabric Structure
Made by interlocking two ribbed structures, with alternating face and back loops across adjacent courses.
Constructed on double-bed knitting machines, where the needles of the two beds work in perfect alternation.
4. Thickness and Stability
Interlock fabric is thicker, heavier, and more stable compared to other weft knits.
It does not curl at the edges and has a firm, dense texture.
5. Applications
- Commonly used for activewear, sportswear, outerwear, and premium knit garments requiring durability and a smooth finish.
6. Notation of interlock knit structure
7.End use
Interlock structures are use for– Underwear, shirts, suits, trouser suits, sportswear, dresses etc.
Conclusion
Understanding the basics of weft knit structures is essential for anyone interested in textile and fabric design. These structures, including plain, rib, interlock, and purl, each offer unique characteristics and applications. By mastering the different types of weft knit structures and their representations, one can effectively choose the right fabric for specific garments and uses. Whether it's the stretchability of plain knits, the elasticity of rib knits, the reversibility of purl knits, or the stability of interlock knits, each structure provides distinct advantages that cater to various fashion and functional needs.