How Wool Is Graded: The Bradford Count and Micron System

How Wool Is Graded: The Bradford Count and Micron System

Wool grading is the systematic classification of wool based on the fineness of its fibers. This process is essential for determining the value and end-use of the wool. The two primary systems for this purpose are the Bradford Count, a historical method based on yarn yield, and the micron system, a modern, scientific measurement of fiber diameter. While the Bradford Count provides a foundational understanding of wool quality, the micron system is the current industry standard, offering a precise and objective measure.

The Bradford Count System: A Legacy of Subjectivity

The Bradford Count, also known as the Spinning Count or English Worsted Yarn Count System, originated in the 19th century in Bradford, England, which was then the epicenter of the global wool trade. This system is founded on the principle of estimating the yarn yield from a given amount of wool. Specifically, the Bradford Count number represents the theoretical number of 560-yard hanks of yarn that can be spun from one pound of clean, combed wool. A higher count number indicates a finer wool, which means more fibers are present per unit of weight, allowing for a greater length of yarn to be spun. For instance, a pound of 64s Merino wool was expected to yield 64 hanks of yarn, a significant output that reflected its high quality.

The Bradford system, while innovative for its time, is inherently subjective. Its accuracy depends heavily on the skill and experience of the wool sorter, who assesses the wool’s fineness through visual inspection and touch. This manual assessment, while a craft in itself, is prone to human error and inconsistency. Furthermore, the Bradford Count does not formally account for other critical fiber characteristics that influence yarn quality, such as crimp (the natural waviness of the fiber), staple length, and strength. Crimp, in particular, plays a significant role in the spinning process, affecting the elasticity and bulk of the yarn. Due to these limitations, the Bradford Count is now largely considered a legacy system. However, its terminology is still prevalent in some sectors of the wool industry, and it provides a valuable historical context for the evolution of wool grading.

The Micron System: A Standard of Precision

The micron system is the modern, scientific standard for grading wool, providing an objective and precise measurement of fiber diameter. A micron (µm) is a unit of measurement equal to one-millionth of a meter. The micron system directly measures the mean diameter of the wool fibers, offering a definitive assessment of their fineness. The lower the micron count, the finer the fiber, and consequently, the softer and more comfortable the resulting fabric will be against the skin.

The development of the micron system was made possible by advancements in technology, particularly in microscopy and automated fiber measurement. The Optical Fiber Diameter Analyzer (OFDA) is a key instrument in modern wool grading. It can analyze thousands of individual fibers in a matter of seconds, providing a detailed statistical analysis of the fiber diameter distribution. This includes the mean micron count, the standard deviation, and the coefficient of variation, which are all critical parameters for determining the quality and consistency of the wool.

The precision of the micron system has had a profound impact on the wool industry. It has enabled wool growers to make more informed breeding decisions, selecting for sheep that produce finer and more consistent fleeces. For textile manufacturers, the micron system provides the data needed to engineer fabrics with specific properties, from ultra-fine knitwear to durable outerwear. The table below, established by the U.S. Department of Agriculture (USDA), illustrates the relationship between the old “Blood” system grades and the modern micron ranges.

From Blood to Bradford: The Evolution of Wool Grading

The history of wool grading is a fascinating journey that mirrors the technological and industrial advancements of the past two centuries. Before the Bradford Count, the “Blood System” was the primary method of wool classification in the United States. This system, which emerged in the early 1800s, graded wool based on the perceived percentage of Spanish Merino sheep genetics in a flock. The Spanish Merino was universally recognized for producing the finest wool, and thus, a “full-blood” Merino was the benchmark for quality. Other wools were graded in fractions, such as “1/2 blood,” “3/8 blood,” and “1/4 blood,” to indicate their supposed genetic proximity to the purebred Merino.

The Blood System was even more subjective than the Bradford Count, relying on broad estimations and lacking any standardized methodology. As the textile industry grew and demanded greater consistency, the need for a more reliable grading system became apparent. The Bradford Count, with its more systematic approach, was a significant improvement, but it was the advent of the micron system that truly revolutionized the industry. The transition from the Blood System to the Bradford Count, and finally to the micron system, represents a clear progression towards greater precision, objectivity, and scientific rigor in the assessment of wool quality.

Understanding the Nuances: Beyond the Numbers

While the micron count is the most important factor in determining the fineness and softness of wool, it is by no means the only one. A comprehensive understanding of wool quality requires a consideration of several other key characteristics:

• Crimp: Crimp refers to the natural wave or curl of the wool fiber. It is a crucial characteristic that provides elasticity, resilience, and bulk to the yarn and the final fabric. A well-defined crimp allows the yarn to trap more air, which enhances its insulating properties. The frequency and amplitude of the crimp vary between different sheep breeds and are important considerations in the spinning process.
• Staple Length: The staple length is the length of the individual wool fibers. Longer staple lengths are generally preferred for worsted spinning, a process that produces a smooth, strong, and lustrous yarn. Shorter staple lengths are more suited for woolen spinning, which results in a softer, bulkier, and hairier yarn.
• Color: The natural color of the wool is another important factor. While wool comes in a range of natural colors, from white and cream to brown and black, whiter wools are generally more desirable. This is because they can be dyed to a wider and more vibrant spectrum of colors, offering greater versatility in textile design.
• Strength: The tensile strength of the wool fibers is a measure of their ability to withstand tension without breaking. Stronger fibers are more durable and less likely to break during the manufacturing process, resulting in a higher quality and more long-lasting product.

At SELVANE, our commitment to Radical Crafts is reflected in our meticulous approach to material selection. We utilize this comprehensive understanding of wool quality to source only the finest materials for our products. We work in close partnership with suppliers who adhere to the highest standards of wool grading, ensuring that every garment we create is crafted from wool of exceptional quality, softness, and durability. For a deeper insight into our material philosophy, please see our page on Our Materials.

Frequently Asked Questions

What is the difference between the Bradford Count and the micron system?

The Bradford Count is a historical, subjective system based on the theoretical yarn yield of a pound of wool. It was a significant step in standardizing wool grading but has been largely superseded by the more precise micron system. The micron system is a modern, scientific measurement of the actual diameter of the wool fibers. Its objectivity and accuracy have made it the current industry standard.

Is a lower micron count always better?

A lower micron count indicates a finer, softer wool, which is generally more desirable for next-to-skin apparel. However, the ideal micron count depends on the intended use of the wool. For instance, while a fine Merino wool with a low micron count is perfect for a soft sweater, a more robust wool with a higher micron count would be better suited for a durable coat or a resilient carpet. The choice of micron count is therefore a balance between softness and performance.

How is wool graded for commercial use?

For commercial use, wool is graded using a combination of the micron system and other quality assessments. After shearing, the fleece is “skirted” to remove any stained or inferior wool from the edges. The remaining fleece is then graded by a certified wool classer, who assesses the fiber diameter (micron), staple length, strength, color, and cleanliness. The wool is then pressed into bales and labeled with its quality specifications, ready for sale to textile manufacturers.

What is the future of wool grading?

The future of wool grading is likely to involve even greater precision and automation. New technologies are being developed that can provide a more detailed analysis of wool fiber characteristics, including the distribution of fiber diameter along the staple and the presence of any medullated (hollow) fibers. These advancements will allow for an even more precise matching of wool to its end-use, further enhancing the quality and performance of wool products.

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