The fabric elasticity percentage is an important characteristic to consider.
Before cutting the pieces of a garment, you need to calculate the elasticity percentage of the fabric. Then you will verify if it matches the pattern measurements. Otherwise, the fit of the garment won’t be right.
The measurements of the pattern are adjusted according to the elasticity of the selected fabric: the higher fabric elasticity, the smaller will be the pattern.
Elasticity and Recovery
Before continuing, we need to define what is the Elasticity, as a consequence, the Recovery factor.
Elasticity:
It is the result of stretching a piece of fabric to the maximum without causing any deformation.
The elasticity is measured as a percent per meter (or inch).
Fabric elasticity can be measured wide-wise, long-wise, or across the bias of the fabric. It can also be measured across several senses at the same time, with the chance their measure is different.
Recovery (or Bounce):
It is the recovering capacity after being stretched.
Fabrics with high bounce, are those that recover their original measurements.
If the fabric does not recover its original measurements, the garment will lose its shape as long as it is used.
4 Way Stretch Fabrics (2 directions):
It refers to the fabrics stretches in both directions, crosswise and lengthwise.
FORMULA
How to calculate the elasticity?
To calculate the elasticity of a fabric:
- Cut a fabric sample of 25cm x 25cm (swatch).
- To check elasticity on the width line, fold the piece in half following the grainline direction.
- Stretch the fabric and measure it.
- Once the fabric is flat and relaxed, measure it again to check if it has recovered its measurements while in relaxation.
To calculate the elasticity on length or bias line, repeat the method by folding the piece of fabric to the crosswise or bias line.
Elasticity Percentage: the Formula
The elasticity percentage is calculated by the following formula:
Elasticity Percentage = (Final Measurement – Initial Measurement) / Initial Measurement x 100
For example, a piece of fabric that measures 1 meter it stretches 125 centimetres, will have an elasticity of 25%:
125-100 = 25 25/100 = 0.025 0.25 X 100 = 25%
If the swatch measures 25cm x 25cm, the calculation will be:
31.25-25 = 6.25 6.25 / 25 = 0.25 0.25 x 100 = 25%
Formula and Pattern: Application
If the fabric stretches widthwise only, we will apply the elasticity percentage to the across measurements (widths and contours).
The main measure of the clothing will be the reference. For example, a t-shirt with a chest contour of 84cm.
If the fabric elasticity is 25%, so the chest contour of the pattern must be reduced to 63cm.
84 – 25% = 63
If the t-shirt is made of two patterns, then the chest contour on each pattern will be reduced 10.5cm each.
The rest of the widthwise measurements are reduced following the same proportion. However, longwise measures will remain as the original pattern.
But if the fabric stretches in two directions, the formula will be applied in both directions, applying the proper percentage to each one.
Olga Fuenmayor
Editor at Seampedia.
Fashion Technical Management / Consulting
Model development / Quality control / Production control.
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