Changing Yarn Count to Make Cloth Heavier or Lighter
This rule is used when we want to make a new cloth of the same character, but with a different weight, by changing the yarn count.
In simple words, it answers this question:
If I want the same type of fabric, but heavier or lighter, what yarn count should I use?
Here, “same character” means the cloth should remain similar in general construction, appearance, handle, and fabric type. The main change is only in the weight of the cloth.
Meaning of the Rule
The rule says:
The yarn count changes in inverse proportion to the square of the cloth weight.
In the old wording:
As the square of the weight of the required cloth is to the square of the weight of the given cloth, so is the yarn count of the given cloth to the yarn count of the required cloth.
In formula form:
Required yarn count / Given yarn count = (Given cloth weight)2 / (Required cloth weight)2
Or:
Required yarn count = Given yarn count × (Given cloth weight)2 / (Required cloth weight)2
The important point is this:
If the cloth becomes heavier, the yarn count becomes lower/coarser.
If the cloth becomes lighter, the yarn count becomes higher/finer.
This is because, in cotton count and many indirect count systems, a lower count means a thicker yarn, and a higher count means a finer yarn.
Example Given
A cloth is made with:
20s warp
Now we want to make a cloth of the same character, but:
One-sixth heavier
This means the original cloth had 6 parts of weight. If it becomes one-sixth heavier, its new weight becomes:
6 + 1 = 7 parts
So the weight relationship is:
Given cloth weight : Required cloth weight = 6 : 7
Or in the form used in the rule:
Required weight : Given weight = 7 : 6
Applying the Rule
The rule says:
72 : 62 :: 20 : x
That means:
49 : 36 :: 20 : x
So:
x = (36 × 20) / 49
x = 720 / 49
x = 14.69
So the required yarn count is approximately:
14.7s
In practical terms, this would be taken as nearly:
15s
Therefore, to make the cloth one-sixth heavier, the warp should be changed from 20s to about 15s.
Why Does the Count Become 15s?
At first, it may seem surprising that increasing the cloth weight by only one-sixth changes the yarn count from 20s to about 15s.
But the rule uses the square of the weight ratio, not the simple weight ratio.
The required cloth is heavier in the ratio:
7 : 6
So the yarn count changes in the ratio:
62 : 72
That is:
36 : 49
Therefore:
20 × 36 / 49 = 14.69
Since the required cloth is heavier, the yarn must be coarser. In cotton count, coarser yarn has a lower count, so 20s becomes approximately 15s.
Understanding “One-Sixth Heavier”
This part is very important.
If a cloth is made one-sixth heavier, it does not mean the ratio is 6:5. It means the original cloth had 6 parts, and one more part is added.
Original weight = 6
Increase = 1
New weight = 7
Therefore, the proportion is:
7 : 6
That is why the calculation uses:
72 : 62
If the cloth were made one-seventh lighter, then the reverse would apply. The required cloth would be lighter than the original, so the yarn count would need to become finer, meaning a higher count.
Why the Count System Does Not Matter
This means the rule is not limited to cotton count, worsted count, linen count, or any other specific yarn count system. The rule is based on proportion.
So whether the yarn is expressed as 20s cotton, 20s worsted, or any other count system, the proportional calculation remains the same, provided the same count system is used consistently throughout the calculation.
The rule is concerned with the relationship between:
Cloth weight and yarn fineness/coarseness
It is not primarily concerned with the material itself.
Simple Interpretation
If we want to make the same type of cloth heavier, we need a thicker yarn.
If we want to make the same type of cloth lighter, we need a finer yarn.
But the change is not calculated directly by simple proportion. It is calculated using the square of the weight ratio.
Heavier cloth ⇒ lower yarn count
Lighter cloth ⇒ higher yarn count
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In Simple Terms
A cloth made with 20s yarn is to be made one-sixth heavier while keeping the same character. Since one-sixth heavier means the weight changes from 6 parts to 7 parts, we use the squared ratio:
72 : 62 :: 20 : x
This gives:
x = 14.69
So, the required yarn count is nearly 15s.
Therefore, to make the fabric one-sixth heavier, the yarn must be changed from 20s to about 15s, because 15s is coarser and will produce a heavier cloth.
Having found the counts required, it will be necessary now to find the ends per inch of that count which will produce a cloth of the same character as the given cloth. Please continue here to read more.
