Wool Grading

The American or Blood System The American system of grading wool was developed in the early 1800s when the native coarse-wooled sheep were being bred to finewooled Merino rams imported from Spain. It assumes that the offspring of the cross would have fleeces which were intermediate in fineness between the two parents. The wool grade is defined as the percentage of Merino blood carried by the sheep that typically would produce a particular fineness of wool. The grade or fiber diameter came to be expressed as fine, 1/2-blood, 3/8blood, 1/4-blood, low 1/4-blood, common and braid (Figure 1). Today, these terms are not as exact as the trade would prefer, and the spread within a grade is too broad to suit the purposes of wool processors.