Some people try to count sheep when they go to bed. For others, however, a good night's sleep only comes from thinking about yarn count. Before any textile, including bed sheets, can be made, the manufacturers have to produce the yarn. The quality of a sheet depends on its yarn count, which is a numerical value that tells you how fine or coarse a yarn is. In technical terms, it's the value of the linear density (the diameter) to which that yarn was spun. When helping you fall asleep, this is the count that will matter.
Calculating Yarn Count
The yarn count can tell you a lot about a yarn's durability, strength, and comfort. It's an important number, and that means it's one that you don't want to estimate. You can probably guess where this is going. We're going to have to talk about math and in a textiles course, no less.
In its most basic sense, the yarn count represents either the mass per unit length, or length per unit mass of the spun yarn. Let's look at two different ways to calculate this number, both of which can ultimately tell us how fine or coarse the yarn is but involve different routes of getting there.
Let's start with the first method for calculating yarn count: the direct system, which calculates the weight of a yarn by treating the length of the yarn as the constant in the formula. Basically, it helps you answer the question, 'How much does a consistent length of yarn weigh?' That's what the yarn count represents. In this system, a higher yarn count represents a heavier and, therefore, coarser yarn.
The basic formula for the direct system looks like this:
N = (W/l) / (L/w)
In this formula, N is the Yarn Count, W is the weight of a sample of yarn, l is the unit of length, L is the length of the sample, and w is the unit of weight. W and L come from the specific yarn being used, but what about w and l? These numbers come from the metric we're using to calculate yarn count. Here are three units we often use in the direct system:
Tex: Grams per 1000m (1 km) of yarn
Denier: Grams per 9000m (9 km) of yarn
Pounds per Spindle: Pounds per 14,400 yards of yarn
For example, a Tex would be the weight in grams in one kilometer of yarn. In our formula for the direct system, the unit of length would be one kilometer, and the unit of weight would be a gram. From there, all we need is the actual weight and length of the sample, and we can calculate the yarn count.