One of the development issues that we get asked about a lot is fabric shrinkage.
Here is some info about the subject.
When should I do a shrink test?
I would recommend to do a shrink test to every fabric that you are looking to use.
How to preform a shrink test?
Create a square pattern piece of 12.5" by 12.5"
Put the pattern piece on the fabric that you are testing and cut the square out of the fabric.
Using a permanent marker mark the warp (length of the fabric) with an arrow
Run the fabric through the your shrinkage process (re: washing, ironing, dying etc.).
Lay it flat on your cutting table (if you are testing washed denim do not steam or Iron the fabric after the wash cause it will effect the measurements).
Measure the fabric in both directions.
How to calculate the shrinkage percentage?
If the fabric shrunk, calculate the % of shrinkage using the following formula: every 1/8" of shrinkage is accounted as 1% shrinkage. For example, if the weft measured after the wash 12 1/8" that means a shrinkage of 3/8" in the weft = 3% shrinkage.
I tested the fabric and found out that it shrinks, how do I solve the issue for production?
You can use one of these two solutions:
Building the Shrinkage % back into the pattern (your grader can do that digitally)
Pre-shrinking the fabric prior to cutting your production.
Which solution is right for me?
When the shrinkage % is in one direction only and measures up to 7-8%, you can built this % back into the pattern.
However, if the % is more than 7-8% I would recommend the second option of preshrinking the fabric before cutting.
When the shrinkage is in both directions of the fabric, it will depend on the shrinkage % in each direction. If the shrinkage is not quite even between the 2 directions re: weft is 1% and warp is 10%, than it will depending on the actual style but you might need to preshrink the fabric (ask your grader for their recommendation).
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