Applying Cloth Weight Rules to Both Warp and Weft
The earlier calculations and rules were explained mainly with reference to warp yarns. However, the same rules are equally applicable to weft yarns.
The only change is in terminology. For warp, we speak of ends per inch. For weft, we speak of picks per inch. The principle of calculation remains exactly the same.
Therefore, when a whole cloth is to be made heavier or lighter while keeping the same character, both the warp and the weft must be adjusted proportionately.
Earlier, the rules were used to find the new warp count and the new ends per inch. But a real woven cloth usually contains both warp and weft.
Warp means the lengthwise yarns in the fabric.
Weft means the crosswise yarns inserted during weaving.
If the cloth weight is to be increased or decreased while preserving the same fabric character, then the following must be recalculated:
The warp count must be changed.
The weft count must be changed.
The ends per inch must be changed.
The picks per inch must be changed.
This keeps the cloth balanced. Otherwise, the fabric may become too dense, too loose, too stiff, or quite different in handle and appearance.
Given Example
The original cloth is made with:
| Part of Cloth | Original Construction |
|---|---|
| Warp | 56 ends per inch of \(2/30s\) yarn |
| Weft | 60 picks per inch of single \(18s\) yarn |
The requirement is:
Increase the weight by one-fifth.
So we need to find the new warp count, new weft count, new ends per inch, and new picks per inch.
Step 1: Convert the Folded Warp Yarn to Equivalent Single Count
The warp yarn is given as:
\(2/30s\)
This means that two yarns of \(30s\) count are folded or twisted together.
In an indirect count system, when two equal yarns are folded together, the equivalent count becomes half.
\(2/30s = 15s\)
Therefore, the warp behaves like a single yarn of approximately:
\(15s\)
So:
Given warp count \(= 15s\)
Given weft count \(= 18s\)
Step 2: Understand “Increase the Weight by One-Fifth”
If the cloth is to be made one-fifth heavier, the original cloth weight may be treated as 5 parts.
An increase of one-fifth adds 1 more part.
\[ \text{Original weight} = 5 \]
\[ \text{Increase} = 1 \]
\[ \text{Required weight} = 6 \]
Therefore, the required cloth weight and given cloth weight are in the ratio:
\[ \text{Required weight} : \text{Given weight} = 6 : 5 \]
Step 3: Find the New Warp Count
The rule for finding the required yarn count is:
\[ \text{Required count} = \text{Given count} \times \frac{(\text{Given weight})^2}{(\text{Required weight})^2} \]
For warp:
\[ \text{Given warp count} = 15s \]
\[ \text{Given weight} = 5 \]
\[ \text{Required weight} = 6 \]
Therefore:
\[ x = 15 \times \frac{5^2}{6^2} \]
\[ x = 15 \times \frac{25}{36} \]
\[ x = \frac{375}{36} \]
\[ x = 10.42 \]
So the required warp count is approximately:
\[ 10.4s \]
In the old notation, this may be written as about:
\[ 10 \frac{5}{12}s \]
So the warp changes from:
\[ 15s \rightarrow 10.4s \]
Since the fabric is becoming heavier, the yarn count becomes lower, meaning the yarn becomes coarser.
Step 4: Find the New Weft Count
The original weft count is:
\[ 18s \]
Using the same rule:
\[ x = 18 \times \frac{5^2}{6^2} \]
\[ x = 18 \times \frac{25}{36} \]
\[ x = \frac{450}{36} \]
\[ x = 12.5 \]
So the required weft count is:
\[ 12.5s \]
The weft changes from:
\[ 18s \rightarrow 12.5s \]
Again, because the cloth is becoming heavier, the weft yarn also becomes coarser.
Step 5: Find the New Ends Per Inch
Once the warp count is changed, the sett must also be adjusted. For this, we use the shortcut rule:
\[ \text{Required weight} : \text{Given weight} :: \text{Given ends} : \text{Required ends} \]
Here:
\[ \text{Required weight} = 6 \]
\[ \text{Given weight} = 5 \]
\[ \text{Given ends} = 56 \]
Therefore:
\[ 6 : 5 :: 56 : x \]
\[ x = \frac{56 \times 5}{6} \]
\[ x = \frac{280}{6} \]
\[ x = 46.67 \]
So the new ends per inch should be approximately:
\[ 46.7 \]
In practical terms, this may be taken as:
47 ends per inch
The number of warp threads per inch is reduced because the new warp yarn is coarser.
Step 6: Find the New Picks Per Inch
The same rule is applied to weft, but instead of ends per inch, we use picks per inch.
\[ \text{Required weight} : \text{Given weight} :: \text{Given picks} : \text{Required picks} \]
Here:
\[ \text{Required weight} = 6 \]
\[ \text{Given weight} = 5 \]
\[ \text{Given picks} = 60 \]
Therefore:
\[ 6 : 5 :: 60 : x \]
\[ x = \frac{60 \times 5}{6} \]
\[ x = 50 \]
So the required picks per inch are:
\[ 50 \]
The weft sett changes from:
\[ 60 \text{ picks per inch} \rightarrow 50 \text{ picks per inch} \]
Final New Cloth Construction
The original cloth was:
| Part | Original Construction |
|---|---|
| Warp | \(56\) ends per inch of \(2/30s\) yarn |
| Weft | \(60\) picks per inch of \(18s\) yarn |
The new cloth, one-fifth heavier, should be approximately:
| Part | New Construction |
|---|---|
| Warp | \(46.7\) ends per inch of \(10.4s\) equivalent warp |
| Weft | \(50\) picks per inch of \(12.5s\) weft |
Since the original warp was a folded yarn, we should remember that the new warp count is the equivalent single count. If it is again to be made as a two-fold yarn, then the folded yarn must be chosen so that its resultant count is about \(10.4s\).
For example, a two-fold yarn close to that might be:
\[ 2/21s \]
because:
\[ 2/21s = 10.5s \]
So, in practical mill terms, the new warp could be approximately:
\(2/21s\) warp and \(12.5s\) weft
Why Ends and Picks Are Reduced
This is the most important point.
To make the cloth heavier, we are using coarser yarns.
\[ \text{Warp: } 15s \rightarrow 10.4s \]
\[ \text{Weft: } 18s \rightarrow 12.5s \]
Because the yarns are thicker, we cannot keep the same number of ends and picks per inch. If we did, the fabric would become too heavy and too crowded.
So the sett is reduced:
\[ \text{Ends per inch: } 56 \rightarrow 46.7 \]
\[ \text{Picks per inch: } 60 \rightarrow 50 \]
This keeps the fabric in the same general character while increasing the total weight by one-fifth.
Why the Rules Apply to Any Yarn Count System
There is a very important general point: these rules are not restricted to cotton counts.
They apply to any yarn-counting system because the calculation is based on proportion.
The author avoids referring to a particular yarn class or count system because the principle is general. It can apply to cotton, worsted, linen, silk, or any other yarn system, provided that the same system is used consistently.
However, one condition is important: the new cloth must be made from the same class of yarn as the original cloth.
That means if the given cloth is made from cotton yarn, the required cloth should also be calculated as cotton yarn. If it is worsted, it should remain worsted. If it is linen, it should remain linen.
Changing from one class of yarn to another is a different problem because different fibres and yarn systems behave differently. That is why separate rules are needed for changing from one class of yarn to another.
In Simple Terms
The earlier rules for changing yarn count and sett are not only for warp. They also apply to weft.
For a whole cloth, both warp and weft must be recalculated.
In the example, the original cloth was:
\[ 56 \text{ ends per inch of } 2/30s \text{ warp} \]
\[ 60 \text{ picks per inch of } 18s \text{ weft} \]
The required cloth is one-fifth heavier. The final result is:
\[ \text{Warp count: } 15s \rightarrow 10.4s \]
\[ \text{Weft count: } 18s \rightarrow 12.5s \]
\[ \text{Ends per inch: } 56 \rightarrow 46.7 \]
\[ \text{Picks per inch: } 60 \rightarrow 50 \]
So, the whole cloth becomes heavier, but because both yarn count and sett are adjusted proportionately, it remains of the same general character.
