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Developing the Premier Colored Huacaya Alpaca Herd in the World

The Role of Crimp
in the Textile Process

Mike Safley

The term crimp has become very familiar to alpaca breeders. Crimp is defined as the natural wave formation of the fiber and is expressed as waves or crimps per unit of length. Visually, crimp is most notable in the well-organized staples or locks found in the fleece. Crimp also occurs along the shaft of a single fiber and is defined as crinkle by Cameron Holt of the Melbourne College of Textiles.

In the wool trade, breeders, graders, classers, and manufacturers have traditionally held the view that more crimp means finer fiber. This misperception has been codified into the various count systems used to classify the fineness of sheep's wool. One such system is incorporated into the U.S. Standard Grades of Raw Wool issued by the U.S. Department of Agriculture and is shown in Table 1 below.

 

Table 1. Grade and Crimps in Wool
	Grades		Number of		Grades		Number of
			Crimps per Inch				Crimps per Inch
	Very fine		22 to 30		1/4 blood		5 to 8
	Fine		14 to 22		Low quarter		2 to 5
	1/2 blood		10 to 14		Common		0 to 2
	3/8 blood		8 to 10		Braid		0 to 1

The measurement of fiber has become very sophisticated and objective with the advent of such instruments as the LASER SCAN, OFDA, and air-flow machines. The use of these new measuring devices has disproved many of the myths surrounding the processing qualities of certain fiber traits. For example, it is now well established that crimps per inch is only a rough indicator of fiber fineness.

Today, it is possible to isolate the measurement of crimp and fiber diameter in raw fleece and to separately assess their impact on the quality of the finished product. Questions such as how crimp frequency affects the processing of raw wool and the handle¹ of finished cloth are now being answered by researchers in Australia, Japan, and New Zealand.

Sheep's wool has been the subject of most, if not all, available research with regard to crimp as a processing characteristic. This research is not, by any means, definitive for alpaca fiber. But understanding the role crimp plays in the textile process could be beneficial to alpaca breeders.

Many fiber-bearing animals produce fleece that is utterly devoid of crimp. Fiber from vicuña, the alpaca's original ancestor, has no crimp; nor does suri alpaca fiber, mohair from goats, or angora from rabbits. These fibers are among the most desirable in the world. In other words, the existence of crimp is not necessary to define the value of fiber or create fine garments.

Huacaya alpacas often exhibit crimp in their fleece and, if not crimp, then crinkle. The heritability of crimp in alpacas appears to be very high. Studies of merino sheep indicate a heritability factor of 0.46 for merino flocks selected solely for increased or decreased crimp. If it is proven that a particular type of crimp is a commercially valuable trait, it could easily be selected for genetically, although there may be antagonistic genetic correlations between fleece weight, fiber diameter, and crimp frequency.

Large-scale wool-processing studies using a wide range of wool types from different breeds have demonstrated that 80 to 90 percent of the variation in the processing performance of wool yarn and in the quality of fabrics may be explained by variations in the fiber diameter, crimp, and length of raw fleece. Alpacas have the capacity to produce crimp in their fleece. Assuming that crimp in alpaca fleece is desirable, just as it is in sheep, leads us to consider the nature of crimp and the type of crimp that is most desirable to the textile manufacturer.

THE STRUCTURAL NATURE OF CRIMP²

Wool fiber has two cortical cells, para and ortho. In certain coarse fibers a hollow core (medulla) may be visible. The cortical cells in alpaca fiber constitute a variable percentage of the fiber mass, being the lowest in coarse fibers and the highest in fine fibers, where it may be as high as 90 percent.

Cortical cells are the load-bearing elements of the fiber. The cuticle, or outer scale, imparts the inherent aesthetic qualities of the fiber, such as softness of handle and luster. The entire assembly is held together by a glue called intercellular cement.

Wool fiber has a bilateral structure--that is, the paracortex and orthocortex grow side by side. It is this structure that is believed to give wool its crimp. Think of a single fiber as a rope made of two independent strands twisted together. When twisted ever more tightly, the rope kinks, or "crimps." As noted in Holt, research in 1953 by a Japanese scientist found that the orthocortex was always observed on the outside of the crimp curve, as shown in Figure 1.

Figure 1. Structure of fiber

Villarroel³ found that fine huacaya (not suri) crimped fiber, like wool, has a clearly defined ortho-para differentiation. The cortex of medium-to-coarse alpaca fiber (23 to 35 microns) is less distinct, and the two types of cells break up into segments. In coarse fibers the ortho segment is seldom seen. Suri fiber has no visible bilateral demarcation.

CRIMP COUNT: ALPACA
VERSUS SHEEP

The following discussion of crimp's impact on finished textile products focuses on crimp count and, to a lesser degree, fiber diameter. The sheep's wool used in the processing trials discussed later in this article ranged in diameter from 16.5 to 22.3 microns. The frequency of crimp ranged from a low of 4 crimps per centimeter (low) to a high of 8 per centimeter. Four crimps per centimeter translates into about 10 crimps per inch.

Figure 2. Alpaca fleece sample: crimp frequency and fiber diameter

To keep in perspective the information contained in this article, please refer to Figure 2. The five locks of alpaca fleece pictured have crimp counts ranging from 5 crimps per inch (1.97 crimps per cm) (A) to 7 crimps per inch (2.76 crimps per cm) (E). These counts are considerably lower than the merino fiber used in the processing trials discussed below. To better understand the visual relationship of the crimps per centimeter of the sheep's wool discussed and the alpaca samples pictured, see Figure 3.

Figure 3. Crimp frequency: alpaca versus sheep fiber

The samples depicted in Figure 2 were measured for both micron count and crimp frequency by Yocom-McColl Testing Laboratories in Denver. All five of these samples are from male alpacas. Sample D is from a six-month-old animal; the others are from older breeding males. These tests provide further evidence that crimp count does not accurately predict fineness.

DIFFERENCES BETWEEN SHEEP'S WOOL AND ALPACA FIBER

Substantive differences between sheep's wool and alpaca fiber exist. Alpaca fiber has different scale heights--approximately 0.4 micron versus that of sheep's wool, 0.8 micron. The scale frequency of alpaca is more than sheep's wool--9 per 100 microns versus 4 per 100 microns. Alpaca fiber is also much stronger than sheep's wool. All these differences complicate the transposition of information about the processing of sheep's wool to the processing of alpaca fiber. Some of the information may be pertinent, some may not. Alpaca breeders need to develop research that specifically identifies the commercially valuable fiber traits of the alpaca. The following discussion helps identify traits that have the potential to affect the value of alpaca fiber.

WOOLEN VERSUS WORSTED

Before we begin considering the results of the processing trials discussed in this article, it is important that we look at the difference between the woolen and worsted spinning systems. Crimp affects different qualities in yarn produced by these systems.

Woolen fabrics are characterized as being fuzzy, thick, and bulky. They are made from fibers that are 1 to 3 inches (2.5 to 7.6 cm) in length and that have been carded and not combed (worsted yarns are carded and combed). After the carding process is complete, the woolen "sliver"⁴ is twisted by machine into ropelike strands called roving⁵ and wound onto reels for spinning. Woolen yarns are fluffy and loosely twisted and are used in weaving fabrics such as tweeds and blanket cloth. Woolen fabrics and yarns are traditionally made into bulky garments such as coats and sweaters.

Worsted yarns are spun from longer fibers (3 inches plus) that have been carded, combed, and drawn. Combing machines further straighten the alpaca sliver, making the individual fibers lie parallel. The combing process also eliminates "noils."⁶ The drawing process takes the worsted sliver, doubles it over onto itself, and draws it out again to a thinner, more uniform diameter to ensure that all the alpaca fibers are parallel. Worsted yarns are twisted more tightly and thinly in the spinning process and are manufactured into lightweight fabrics such as gabardine and crepe.

THE ASSOCIATION BETWEEN CRIMP AND COMPRESSION PROPERTIES IN CARDED WOOL AND WOOLEN-SPUN YARNS⁷

Understanding the fiber crimp's influence on the processing properties of wool fiber has been hampered by the lack of appropriate techniques for measuring crimp. Today, there is a scientific method for the routine measurement of the curvature of short snippets of fiber, as reported by P. G. Swan, T. J. Mahar, and J. P. Kenneday from the Division of Wool Technology, CSIRO, Australia. As a result of this new technology, scientists have determined that the crimp, thickness, and compression properties of carded wool are associated.

For the purpose of studying these relationships, eight low-twist, woolen-spun yarns of two different micron counts were spun and analyzed. These samples used blends of crimped and crimpless merino wools of two average fiber diameters. Crimpless fiber was added to crimped fiber in six of the samples. Three samples had 20 percent crimpless fiber, three had 40 percent crimpless fiber, and two contained 100 percent crimped fiber.

The trial showed that the thickness and compressibility of the carded fiber assembly and the resultant yarns are strongly related to the amount of crimp in the wool. The bulk of carded fiber decreases as the percentage of crimpless fiber is increased. There also was a strong relationship between the average curvature (crimp) of short sections of raw fiber and the yarn fiber assemblies. (See Table 2.)

Table 2.8 Measured Average Carded Wool Properties for the Eight Lots
(D = average fiber diameter [19]; K05 = normalized fiber curvature [10]; bulk = core bulk [18]; RC = resistance to compression [17]). Standard deviations are enclosed within parentheses.