GSM is a measurement of fabric weight, but it does not by itself predict how woven interlining will change dimensions. Dimensional stability depends on several factors, including fabric construction, composition, processing conditions, finishing methods and compatibility with the outer fabric.
A woven interlining can be exposed to heat during fusing, pressing or steaming. Moisture can also become relevant through steaming, washing or other processes. Fusing temperature, time and pressure can influence the result. These conditions mean that the same GSM cannot be treated as a guarantee of a particular shrinkage behaviour.
The outer fabric adds another variable. Its fibre, weave and stretch can affect how the fused materials move together. Garment construction can also influence the result through factors such as fusing direction, panel size and seam placement. Because these elements interact, a dimensional-change result from one woven interlining grade should not automatically be applied to another grade or another outer fabric.
The more reliable approach is to test the material under the conditions in which it will actually be used. Record the sample’s original dimensions, process it, allow it to settle and measure it again. Testing the fused pair as well as the interlining can help identify how the complete combination behaves. GSM remains a useful specification, but it should be considered alongside the other factors that influence dimensional stability rather than used as a standalone predictor.
