Changing Cloth Weight and Weave Pattern While Keeping the Same Structure
This post deals with a slightly more advanced fabric-construction problem. Earlier, the rules helped us answer this question:
How do we make the same cloth heavier or lighter while keeping the same pattern?
Now the question is broader:
How do we make a cloth of a different pattern and different weight, but still keep the same structural character?
So, two changes are happening at the same time: the weight of the cloth is changing, and the weave pattern of the cloth is also changing. This makes the calculation more complex.
Meaning of “Equal in Structure”
“Equal in structure” does not mean that the cloth will look exactly the same. Since the pattern is changing, the appearance will also change. It means that the new cloth should preserve a similar structural balance in terms of yarn thickness, thread spacing, firmness, cover, and general fabric character.
In other words, the new fabric should not become too loose, too crowded, too light, or too heavy merely because the weave pattern has changed.
Why Pattern Change Matters
A woven fabric is not determined only by yarn count and ends or picks per inch. It is also affected by the number of intersections between warp and weft.
An intersection happens where warp and weft cross each other. A plain weave has many intersections. A twill weave has fewer intersections. A satin weave has still fewer intersections.
The number of intersections affects the closeness, firmness, flexibility, cover, and weight of the cloth. If there are fewer intersections, the yarns float more freely. Because of this, more threads may be needed to produce a cloth of similar firmness and structure.
So, when the weave pattern changes, the ends and picks per inch must also be adjusted.
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Why the Earlier Method Is Not Enough
One simple method would be to first calculate the new yarn count and threads per inch for the changed weight, assuming that the pattern remains the same. Then, we could adjust the ends and picks for the new pattern using the earlier pattern rule.
But this creates a problem. When the pattern is changed, the weight changes again. For example, changing from a four-end twill to a six-end twill changes the number of intersections and the length of floats. This may require more or fewer threads. That new change in threads then changes the weight again.
So, if we first adjust for weight and then adjust for pattern separately, the second step may disturb the weight obtained in the first step. This means another correction would be needed, and the calculation becomes unnecessarily long.
Therefore, the better method is to combine both changes — weight change and pattern change — in one calculation. This is why the we introduce compound proportion.
Given Example
A cloth is made with the following construction:
| Item | Given Cloth |
|---|---|
| Weave | Four-end twill |
| Warp | 60 ends per inch of 20s yarn |
| Weft | 60 picks per inch of 20s yarn |
The fabric is to be changed to:
| Item | Required Cloth |
|---|---|
| Weave | Six-end twill |
| Weight | One-eighth heavier |
We need to find the required yarn count, required ends per inch, and required picks per inch. Since the warp and weft are the same in the given cloth, the same calculation applies to both.
Understanding the Weight Ratio
The required cloth is to be one-eighth heavier. This means the original cloth weight may be treated as 8 parts.
An increase of one-eighth adds 1 more part.
Therefore:
This is why the calculation uses the numbers 9 and 8.
Understanding the Pattern Factor
Lets compare the two twill structures by considering:
Pattern factor = number of ends in the repeat + number of intersections
For the given four-end twill, the repeat has 4 ends, and the weft passes over and under two ends. The number of intersections is taken as 2.
For the required six-end twill, the repeat has 6 ends, and the weft passes over and under three ends. The number of intersections is again taken as 2.
So the pattern factor is:
This means the required six-end twill has a larger pattern factor than the four-end twill. Because of the longer float structure, the construction must be adjusted to keep the cloth structurally comparable.
Rule:Finding the Required Yarn Count
As the required weight squared is to the given weight squared, and as the ends plus intersections in the given pattern is to the ends plus intersections in the required pattern, so is the given count to the required count.
In simpler formula form:
For this example:
Given count = \(20s\)
Given weight = \(8\)
Required weight = \(9\)
Given pattern factor = \(6\)
Required pattern factor = \(8\)
Therefore:
So the required yarn count is about:
21s
This means that although the cloth is becoming heavier, the pattern change also affects the calculation. The new yarn count does not simply become coarser. Because the six-end twill requires a structural adjustment, the final count becomes slightly finer than 20s.
The pattern change can neutralize or even reverse the effect of the weight change.
Rule Finding the Required Ends and Picks Per Inch
As the required weight is to the given weight, and as the ends plus intersections in the given pattern is to the ends plus intersections in the required pattern, so is the ends per inch in the given cloth to the ends per inch in the required cloth.
In formula form:
For the example:
Given sett = \(60\) ends per inch
Given weight = \(8\)
Required weight = \(9\)
Given pattern factor = \(6\)
Required pattern factor = \(8\)
Therefore:
So the required ends per inch are approximately:
71 ends per inch
Since the weft also originally has 60 picks per inch of 20s yarn, the same calculation gives:
So the required picks per inch are also approximately:
71 picks per inch
Final New Cloth Construction
The original cloth was:
| Item | Original Cloth |
|---|---|
| Weave | Four-end twill |
| Yarn count | 20s |
| Ends per inch | 60 |
| Picks per inch | 60 |
The required cloth is:
| Item | Required Cloth |
|---|---|
| Weave | Six-end twill |
| Yarn count | Approximately 21s |
| Ends per inch | Approximately 71 |
| Picks per inch | Approximately 71 |
Why the Ends Increase Instead of Decrease
This may seem surprising. In earlier examples, when the cloth became heavier, we used coarser yarn and fewer ends. But here, the fabric is not only becoming heavier; it is also changing from a four-end twill to a six-end twill.
The six-end twill has longer floats and fewer binding points per unit of repeat. To maintain the same structural firmness and cover, the fabric needs more threads per inch.
So the pattern change demands more threads. At the same time, the weight increase demands a change in yarn count. When both effects are combined, the final result becomes:
The fabric becomes heavier mainly because there are more threads per inch, even though the yarn itself becomes slightly finer.
Why Compound Proportion Is Better
Compound proportion is useful because it considers two influences at the same time:
Weight change
Pattern change
Instead of adjusting for weight first and then pattern later, it combines both factors into one calculation. This avoids repeated corrections.
If we first calculated for the same pattern and then changed the pattern, the pattern change would alter the weight again. So a further calculation would be required. Compound proportion prevents this.
Applying the Rule to Warp and Weft
The same rule applies to both warp and weft.
| For Warp | For Weft |
|---|---|
| Use warp count | Use weft count |
| Use ends per inch | Use picks per inch |
If warp and weft are different, calculate them separately. If warp and weft are the same, as in this example, the same result applies to both.
General Nature of the Rule
It is again emphasized that the rule is based on proportion. Therefore, it is not limited to one fibre, one yarn type, or one count system.
It can be applied to cotton, wool, silk, linen, or any other yarn, provided the same type of yarn and the same counting system are used consistently.
The same applies to sett systems. Whether the fabric closeness is expressed as ends per inch, picks per inch, or another equivalent sett system, the proportional logic remains the same.
In Simple Terms
This rule is used when both the weight and the weave pattern of a cloth are changed.
If only the weight changes, the earlier rules are enough. But if the pattern also changes, the pattern affects the number of intersections and therefore affects the required number of threads.
In the example:
Final result:
Yarn count = about 21s
Ends per inch = about 71
Picks per inch = about 71
So, the new cloth becomes one-eighth heavier and changes to a six-end twill, while still remaining structurally comparable to the original cloth.
