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Developing the Finest 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 handle ¹ 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 CRIMP ²

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

Villarroel ³ 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.
	Lot	D (um)	Crimpless Fiber (%)	K05 (mm-05)	Bulk (cm)	RC (N.gm-1)
	1	19.0	0	1.43 (0.27)	4.24	6.93
	2	19.0	20	1.30 (0.34)	3.82	6.43
	3	19.0	40	1.15 (.0.39)	3.27	5.89
	4	22.3	0	1.22 (0.29)	3.88	6.43
	5	22.3	20	1.11 (0.33)	3.45	6.13
	6	22.3	20	1.12 (0.28)	3.40	6.05
	7	22.3	40	1.06 (0.33)	3.11	5.70
	8	22.3	40	1.04 (0.29)	3.12	5.66

The study results demonstrate that fiber crimp persists throughout the carding and spinning operations in the woolen system, although the amount of crimp is reduced as fibers react to the strains imposed during the yarn-making process. The average curvature (crimp) of fibers was reduced by approximately 10 percent.

The study also found that the remaining residual curvature (crimp) exerts a substantial influence on the bulk density of unrelaxed low-twist woolen yarns. This means that yarn manufacturers may, simply by sourcing wools of high crimp, reduce the weight of woolen yarns while maintaining an increase in yarn bulk without a corresponding increase in weight.

This study makes the case for the economical use of high-crimp-frequency wool in the woolen process. But before jumping to the conclusion that breeding for highly crimped alpaca fiber is the ideal, we need to consider the value of low-crimp-frequency wool in the worsted process.

The findings of the studies below may provide a glimpse as to why alpaca is considered to have superior handle over wool of a similar diameter. These studies illustrate the complexity of the contribution that crimp makes to the final textile product. The impact of crimp frequency on the values of woolen yarn is different than it is on worsted yarn.

THE BENEFICIAL EFFECTS OF
LOW FIBER CRIMP IN WORSTED PROCESSING AND ON FABRIC PROPERTIES AND FABRIC HANDLE⁹

Studies of the fiber factors that are associated with soft handle in unprocessed wool (greasy wool or clean carded wool) have shown that softness increases with decreasing fiber diameter and with decreasing fiber crimp. Considerable variation in crimp can be found in wools of the same mean fiber diameter. The textile trade's preference has been for higher crimp frequency. This traditional view holds that higher crimp in finer apparel wools produces softer and smoother finished fabrics.

In contrast to this long-held view, controlled experimental trials tracing the softness of wools in the raw state to finished fabric highlight the persistence of softness as a result of lower fiber crimp, in addition to finer fiber.

Eight samples of cloth were manufactured from higher- and lower-crimp wools in fine (20.5 um) and superfine (18.5 um) merino. This fabric was used to determine the handling properties that result from processing wools of different diameter and crimp combinations. The average staple crimp frequencies were about 12.5 crimps per inch (5 per cm) in the low-crimp cloth and about 20 crimps per inch (8 per cm) in the high-crimp cloth. These crimp styles represent differences normally occurring in commercially available fine wools.

The study came to the following conclusions about the difference between the various samples:

• The higher-crimp wools were not as soft in the raw and scoured state as the lower-crimp wools of the same diameter.

   

• The lower-crimp wools had increased hauteur¹⁰ (length) in the top¹¹ produced, which was 2 to 3 mm longer than that of the higher-crimp wools of the same diameter, staple length, and strength.

   

• The 18.5 um wools produced tops about 3 mm shorter than the 20.5 um wools of the same crimp, staple length, and strength.

   

• During spinning, the lower-crimp wools were easier to draft and produced slightly more even yarns.

The subjective assessments of the various pieces of cloth (see Table 3) demonstrated that superior fabrics were made from wools of lower crimp and/or finer diameter. In particular, twill fabrics made from the higher-crimp wools were thicker and rougher than the equivalent fabrics from the lower-crimp wools. The difference in surface smoothness was evident in the handle tests. The higher-crimp fabrics were stiffer in shear and generally less elastic. At the same crimp frequency, fabrics made from higher-diameter wools were rougher, stiffer, less extensible, and less resilient in compression ¹² than the lower-diameter fabrics.

Table 3. Distribution of Preferences in Subjective Comparisons of Fabric Pairs
Differing in Diameter (D) and/or Crimp (C)13
Low diameter indicates 19 um or less; low crimp indicates staple crimp frequencies < 6 crimps.cm-1.
Significance in chi-square test of independence (P < 0.05, p < 0.01, p < 0.001).
		Preference	Softer	Thicker	Smoother	More Resilient
CRIMP-only comparison (n = 8 subjects * 11 fabric pairs)
	Low C	59	42	20	54	33
	High C	29	45	59	33	48
	No choice		1	9	1	7
DIAMETER-only comparison (n = 8 subjects * 9 fabric pairs)
	Low D	61	46	33	55	23
	High D	11	24	34	15	43
	No choice		2	5	2	6
MIXED comparison (n = 8 subjects * 7 fabric pairs)
	Low D + High C	37	35	38	32	20
	High D + Low C	19	18	14	22	29
	No choice		3	4	2	7
ADDITIVE comparison (n = 8 subjects * 4 fabric pairs)
	Low D + Low C	28	23	9	27	9
	High D + High C	4	8	20	5	21
	No choice		1	3		2

Some of the judges who assessed the fabrics commented on the "coolness" of feel in the lower-crimped fabrics. The thinner and, therefore, denser fabrics made from the lower-crimp wools may have a greater degree of fiber-to-skin contact when touched, thus allowing for a faster exchange of heat.

Fabrics made from higher-crimp wools were perceived as thicker, less smooth, and possibly more resilient than equivalent fabrics from lower-crimp wools. Similarly, finer wools produced fabrics that were perceived as softer, smoother, and less resilient than equivalent coarser wool fabrics. These subjective results indicating preference for the handle of the low-crimp cloth were supported by mechanical measurements of fabric bending, shear rigidities, and fabric surface friction.

In sum, the study demonstrated the preference in overall handle for fabrics made from lower-crimp wools over fabrics made from higher-crimp wools. The results also demonstrate that the character that crimp imparts to fabric handle is different from the character contributed by fiber diameter. Fabrics made from finer wools are preferred because of their softness and smoothness, whereas lower crimp imparts smoothness and leanness, and perhaps coolness, to fabric handle. Knowledge of these effects can be used by textile manufacturers to design and engineer fabrics with particular handle characteristics and mechanical properties.

New Zealand AgResearch, Invermay Agricultural Centre, and the Wool Research Technical Division, Nippon Keori Kaishi Ltd., Osaka, carried out a similar study looking at the effect of crimp frequency at the early stages of processing wor-sted yarn. The second stage of the New Zealand study points out the complexity of crimp's role in the handle, feel, and look of garments made of similarly constructed worsted yarn when used in knitted versus woven goods.

EVALUATION OF NEW ZEALAND LOW--
AND HIGH--CRIMP MERINO WOOLS¹⁴

I. Wool Characteristics and Early-Stage Processing Attributes

These tests used shorn fleeces from ninety-eight ewes that were assigned to four processing lots, namely: ultrafine (16.5 microns) high crimp (UH), ultrafine (16.5 microns) low crimp (UL), superfine (19.4 microns) high crimp (SH), and superfine (19.4 microns) low crimp (SL). The low-crimp lots averaged 14.5 crimps per inch (range: 11.7 to 15.5), or 5.7 crimps per cm (range: 4.6 to 6.1), and the high-crimp lots averaged 20 crimps per inch (range: 19.6 to 23), or 8 crimps per cm (range: 7.7 to 9.1).

These fleeces were tested as they were carded, combed, drawn, and spun. The following processing traits were attributable to the different crimp frequencies:

• The percentage of short fibers in tops was markedly lower for low-crimp wools than high-crimp wools.

   

• Neps¹⁵ formation was less in superfine and lower-crimp wools (SL).

   

• Fiber crimp was closely correlated with staple crimp, which indicates that staple crimp may be used to class fleeces into different fiber crimp categories.

   

• Superfine and low-crimp groups produced more clean wool than ultrafine or high-crimp groups.

   

• Clean yield¹⁶ was higher in low-crimp groups.

   

• Lower-crimp wools created tops with more hauteur than high-crimp wools of equal staple length.

Wools with different crimp frequency were shown to have a similar carding performance, but low-crimp wool had better combined performance and produced stronger and softer yarns. This study also noted that most subjective grade and style assessment systems favor high-crimp wools. Most scientific textile trials indicate, however, that high crimp is associated with a deterioration in early-stage processing properties, such as yarn irregularity, extension, and breaking strength.

The New Zealand study on early-stage processing attributes concluded with the following observation: Unless there is widespread acceptance in the textile-processing industry in favor of either low- or high-crimp wool, selection for the trait in merinos is unjustified. However, objective measurements that assist with the identification of low- or high-crimp wools in different styles of fleeces would seem to be of practical benefit to wool processors.

EVALUATION OF NEW ZEALAND LOW--
AND HIGH--CRIMP MERINO WOOLS ¹⁷

II. Wool Characteristics and Processing Performance of Knitwear and Woven Fabrics

The second section of the study dealt with the wool characteristics and processing performance of knitwear and woven fabric made from worsted yarn with different crimp frequencies. The following characteristics of the finished products were attributable to crimp frequency:

• Yarns spun from low-crimp-frequency wools had higher extension and elastic¹⁸ modulus scores. When knitted, they were smoother and had softer handling than high-crimp-frequency wools.

   

• High-crimp-frequency wools, however, resulted in better yarn evenness and fluff index but evidenced greater yarn shrinkage.

   

• Fiber diameter was not significantly related to yarn shrinkage.

   

• Hand evaluation values were higher for both low fiber diameter and low crimp frequency. Rankings for total hand values decreased in order of UL > UH > SL > SH, with low-crimp-frequency lots in each fiber diameter group having a higher handle score than the high-crimp-frequency lots.

   

• Yarns spun from low-crimp-frequency wools are easier to process, could be spun more finely with fewer endbreaks, and have less wastage.

For the yarn and fabric specifications used in this trial, the results showed that fiber diameter and crimp frequency had competing effects on the quality assessments of both the knitted and woven fabrics. Although dependent on construction and finishing, low-crimp-frequency wool woven fabric appeared to be more suitable for summer attire or in women's garments, while high-crimp-frequency wool woven fabric would be more suitable for men's winter clothing.

In conclusion, the authors of the study observed that wool growers should continue to produce a range of wool types that differ in the interrelationships between key fiber characteristics of importance to processing. This diversity will enable designers to be innovative in developing new wool products and also allows processors to select the type of wool best suited to their particular production specifications.

A SUMMARY OF THE VARIOUS PROCESSING TRIALS

The studies reported here are all highly technical in nature and the conclusions understandably varied in some instances, but the results of each were generally consistent in the following regards:

• Higher-crimp wools may be more commercially valuable when used in the woolen process.

   

• Low-crimp, low-micron wools generally demonstrated better "handle" characteristics.

   

• High-crimp wools were better suited for use in heavier winter garments.

   

• Low-crimp wools were better suited for lightweight clothing.

   

• Low-crimp wools were generally easier and more efficient to process than high-crimp wools.

  Many of these conclusions are contrary to popularly held beliefs.

AN ALPACA BREEDER'S LOOK AT CRIMP

Alpaca has far less crimp than merino wool. Based on the conclusions in the above studies, the low crimp frequency in alpaca fiber may partially explain why alpaca is thought to have superior handle when compared to sheep's wool of a comparable micron count. Suri, which has no crimp, is thought to have a smoother handle than both the high-crimp merino and the low-crimp huacaya of a similar micron count.

Alpaca breeders who select for fineness in their breeding programs may also be automatically selecting for crimp or crinkle owing to