Fabric Density

Fabric density indicates the number of warp yarns and weft yarns in 1 inch2. For some countries that use the metric system, the area is 1 cm2 and 2.54 is multiplied to convert it into the correct measurement of density. Although many countries use the metric system, the density is almost always measured in inch. It takes more than just a calculation formula to understand what density really means. It is obvious that thicker fabric would have higher density. Density, however, means a lot more than this.

In a piece of fabric, there are two types of density: warp and weft. Warp is always denser than weft because it is more efficient and cheaper to weave fabrics this way. Fabric with 67 inch and 180 warp end count need 12,069 strands of warp yarns (fabric width × warp end count) to be wound. The huge number of warp yarns is no problem because it only requires more creels to be added to the beam. The smaller units of beams with warp yarns come together to form the whole warp beam.

The horizontal weft yarns, on the other hand, require more work. They have to be woven
back and forth. The reciprocal motion requires more time and energy. Most of fabric production is taken up by weaving these weft yarns. The only way to speed up the production is to use a faster weaving machine with higher RPM (revolution per minute).

In the past, looms looked like wooden ships and had maximum 200 RPM. Modern looms are much more efficient. They can work up to 800 RPM. In a buyer’s perspective, however, it may still be too slow. Since the recent trend in fashion is variety, buying a large amount of available fabric is ineffective. Now the demand in market is fresh fabric, woven and dyed quickly in order to be presented immediately at the customers’ request. Time has become the major factor for succeeding in the fashion industry.

Since weft yarns take up most of the production time, decreasing its number will improve speed as much as using a weaving machine with high RPM. Since both manufactures and buyers accept this fact, most fabrics available in market have more warp end count than weft count.

There are exceptions to this rule­­corduroy and velveteen. These have more weft yarns than warp yarns because the pile construction requires extra weft yarns in addition to those in its ground. Of course, the number of weft yarns in the ground is less than that of warps yarn.
Fabric density is written out in two ways depending on the type of fabric: grey fabric count and finished fabric count. It is difficult to determine the method used just by looking, so one must inquire the mill to make sure. In case of piece dyed cotton fabric, grey fabric count must be used. The same type of cotton fabric will differ in width after going through the finishing process. It is impossible for factories to control such change. This is why the width is shown in a range, 44/5 or 58/60. The possibility of the change that may occur in the finishing process is taken into consideration.

Even an inch of difference is quite significant in terms of density. A piece of fabric with 45 inch width is stretched 1 inch more than that with 44 inch width. Due to this stretch, about 2.2% density is lost. So there is nothing to be happy about if 44 inch fabric turns out to be 45 inch. Density loss means loss in weight and quality as well. So fabrics made with the same standard need to be marked with the grey fabric count. This will help to identify and compare different fabrics as the same type produced by one factory.

In a mill’s point of view, presenting a bigger number is more advantageous in doing business. So some mills use the finished fabric count for indicating cotton density. There is no lie to this since it is the actual density after all, so they say. But I wonder what a smart customer, who knows the difference between the two count methods, will say about this. If finished fabric count must be used, each roll of fabric has to be indicated with its actual width. Writing down a ranged measurement like 44/5 inch will mislead customers to believe that the fabric has been measured with grey count.

There are other ways that finished fabric count can be misleading. For example, lawn fabric’s grey fabric count is 60 × 60, 90 × 88 44/5 inches. Lawn fabric is always indicated in this measurement, no matter what its actual finished count turns out to be. With finished fabric count, however, it could be marked in 103 × 88 44 inches. This will deceive customers to believe it as a better grade of lawn fabric with higher density. One could even write it as 103 × 75, reasoning there are 13 more warp yarns taken out from weft count. The sum of warp and weft count is the same as the original lawn fabric but it actually is lower in quality. These unusual fabrics completely ignore the optimized standards set by the long history of weaving.

They can cause serious problems like shrinkage and tear when made into garments.
Weft count, on the other hand, is controlled by tension. If strong tension is applied when weaving the fabric, the output quantity gets larger than that of the inputted grey. 1,000 yards of grey fabric can be changed to 1,100 yards by having tension. Some cotton mills in the past took advantage of this to increase production without actually increasing the number of yarns.

They were able to gain extra profit by deceiving buyers and consumers. No one bothered to actually measure the fabric density or investigate this matter further. So it has become a custom for mills to control tension to increase weft count.

There is a type of cotton fabric which cannot be measured in grey fabric count­­yarn dyed fabric. Yarn dyed fabrics are finished in a specific pattern. The shape of the pattern cannot be affected by the reduction of width. From the very beginning of weaving stage, yarn dyed fabric is designed for the finish. So its density has to follow the measurement of the finished product.

The quality of polyester is determined by weight rather than density. Polyester always becomes heavier and denser in its final stage of production. Moreover, increasing the density of polyester to a certain degree does not make it proportionally heavier. Therefore, polyester is measured in weight. Sometimes, however, density does matter. It is measured with the unit called“T”when comparing a lighter or heavier version to an existing quality. Similarly, density is not an important factor for measuring knit fabric. A piece of knit fabric is stretchable so density or width is meaningless. Instead, it is measured with yarn count and weight.

It is very rare for expensive fabrics show density. They are measured in fiber composition and fabric weight. A piece of woolen fabric has raised surface, so yarn count is of little importance. Weight, however, is an important factor since it indicates the amount of raw material used. Silk is also one of these expensive fabrics that are measured in weight. For worsted fabric, both yarn count and weight are very important factors in determining its quality.