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Building on the Basics

April 26, 2019

Building on the Basics

Now it's time to expand on the past few topics and apply that information to commercial processing. And it all starts at the sheep! There are slight differences in wool quality on different parts of the sheep's body, and the best sheep produce as much uniform wool as possible. Fiber testing, like we went over last month, helps sheep breeders make breeding decisions to improve the quality and quantity of the wool they produce. 

Both genetics and environment play roles in the quality of wool. Genetic selection helps improve fiber diameter and uniformity. It also helps influence how wool feels next to the skin, since the size and shape of the scales that are on every fiber is affected by genetics. Environment means a lot of things. How the sheep live, whether on the range, in controlled pastures or in an intensively managed indoor pen system. This determines what conditions the sheep encounter. Things like weather, vegetable matter that can get in the wool, the soil conditions and presence or absence of dirts or clays that are difficult to scour out, etc.

Stress levels play a tremendous role as does nutrition. While wool from lambs is very soft, it can be the most delicate. Weaning time is always a stressful event for lambs, even with the most dedicated and compassionate management. Things like over crowding can also create stress which then weakens fiber. Nutrition affects fiber quality in several ways. Poor nutrition, whether its lacking in energy or missing key nutrients, can produce fiber that feels very soft and has a low fiber diameter but is very weak since the animal didn't have what it needed to create strong fiber. Too many calories not only causes the sheep to become overweight, it can produce fiber that's a lot coarser than the animal's genetics would otherwise produce. 

A lot of time and effort goes into managing the environmental and nutritional factors that affect wool growth, since the sheep farmer's livelihood depends on producing wool that's as valuable as possible. It's a symbiotic relationship in many ways. The farmer cares for the sheep and provides the best environmental and nutritional conditions to make the best wool possible. In turn the sheep puts the farmer's efforts into practice and grows the best wool possible. Then the farmer shears the sheep and sells the wool and uses their earnings to provide for their family and herd. 

Now it's time for all of the sheep's and farmer's efforts to pay off: shearing day. This is the first step towards both creating further improvements in the flock and selling the wool. After the sheep in shorn, it's time to skirt the wool.

Skirting is the process of removing any fiber that's not the same as the majority of the fiber and also removing any large amounts of vegetable matter or other contaminants. This information is really important to the farmer, since sheep that yield more high quality fiber are more sustainable. Fiber from the shoulder and body tends to be the highest quality and the most similar in length. Fiber from the belly and legs tends to be coarser and contain more medullated fiber, which tend to be coarser, straighter and prickly. They do serve a very important function: helping the sheep regulate its body temperature by providing room for heat to escape. 

After skirting, it's time to grade or class the fiber. Which term is used depends on where the sheep are raised, with classing more commonly used in Australia. This involves determining how the wool fits a given standard for fiber diameter, yield, length, strength, color and contamination. Fiber diameter is the most important characteristic when determining the value of wool. Length determines which processing path the wool is best suited for. Shorter wool is best suited for the woolen process, while longer wool is best suited for the worsted process. Its also very important that fiber that's going to be processed in the worsted system have the most uniformity of staple length possible. If there's too much variation in staple length, the comb will "read" that as a lot of dissimilar fibers and it will remove the shorter ones. This can lead to a low yielding run, which winds up being more expensive since top making is priced based on the amount of fiber that goes into the process at the beginning. 

There are three systems of grading wool the are used in the fiber industry: the American or Blood System, the British, Bradford or Spinning Count System or the Micron Count system. The Blood System is the oldest and its basis is the amount of Merino genetics that are in a particular sheep. This is based on the idea that each sheep breed was created by humans who were breeding for specific fiber qualities. For example a 100% Merino sheep would produce wool that would be graded as "fine", which refers to the diameter of the wool. A sheep that's 1/4 merino would produce a "1/4 blood" fleece. Its a good basic start for grading, but it doesn't recognize the individual variations in fiber diameter that occur in a particular breed. For example, merino comes in a wide range of fiber dimeters from 25 µm all the way down to the finest merino ever at 11.5 µm.

So, how do we account for this huge variation in the diameter of merino wool? That's what the Bradford System and Micron Count Systems are for. And we'll be talking about those in the next newsletter. 

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