For anyone working with textiles, understanding fabric weight is crucial. GSM, or Grams per Square Meter, is a widely used metric that indicates the weight of fabric per unit area. This seemingly simple value plays a significant role in fabric selection and garment construction. Let’s delve into the world of GSM and explore its importance for woven and knit fabrics.
What is GSM?
GSM stands for Grams per Square Meter. It’s a unit used in the textile industry to express the weight or density of a fabric. In simpler terms, it tells you how much a square meter of that particular fabric weighs in grams.
Here’s a breakdown of why GSM is important:
- Fabric Weight: Higher GSM indicates a heavier fabric, while lower GSM indicates a lighter fabric.
- Fabric Properties: GSM impacts factors like drape, opacity, warmth, breathability, and even durability.
- Fabric Selection: Knowing the GSM helps you choose fabrics suitable for your project’s needs. For instance, a flowy dress might require a fabric with a lower GSM for better drape, while a winter coat would benefit from a higher GSM fabric for warmth.
Why Does Fabric Weight Matter?
GSM directly impacts a fabric’s properties, such as:
- Drape: Heavier fabrics (higher GSM) tend to drape more fluidly, while lighter fabrics (lower GSM) may have a more structured drape.
- Opacity: Generally, fabrics with higher GSM are less see-through. Lighter weight fabrics may require lining depending on the desired level of opacity.
- Warmth and Breathability: Heavier fabrics tend to provide more warmth, while lighter fabrics offer better breathability.
- Durability: While not the sole indicator, GSM can be a general guideline for fabric strength. Heavier fabrics might be more durable for wear and tear.
Working procedure for determination GSM of woven and knitted fabrics:
The procedure for determining the GSM of woven and knitted fabrics differs slightly due to their construction:
Woven Fabrics:
Materials:
- Fabric Sample (Square-shaped, typically 10cm x 10cm)
- Ruler
- Sharp Scissors
- Weighing Scale (accurate to 0.1 grams)
- Calculator (optional)
Steps:
- Sample Preparation:
- Using a ruler and sharp scissors, cut a square-shaped sample from your fabric. A common size is 10cm x 10cm (0.01 square meters). Ensure the sample represents the entire fabric and avoids any irregularities.
- Weighing the Sample:
- Carefully weigh the fabric sample on your weighing scale. Record the weight in grams to the nearest tenth of a gram.
- Calculation:
- Divide the weight of the sample (in grams) by the sample area (in square meters) to obtain the GSM. You can use a calculator or perform the calculation manually.
Formula: GSM = Sample Weight (grams) / Sample Area (square meters)
Example:
- If your 10cm x 10cm (0.01 m²) fabric sample weighs 5 grams, the GSM would be:
GSM = 5 grams / 0.01 m² = 500 GSM
Knitted Fabrics:
For knitted fabrics, their stretchability introduces a slight complication. Their GSM can vary depending on the state (relaxed or stretched) during measurement. Here are two approaches:
1. Relaxed State GSM:
- Follow steps 1 and 2 from the woven fabric procedure.
- Measure and weigh the fabric sample in its natural, unstretched state. This provides a baseline GSM for the fabric.
2. Stretched State GSM:
- Similar to steps 1 and 2, cut and weigh the sample.
- Gently stretch the fabric sample to a slight tension that mimics how it would behave in a garment when worn.
- Record the weight of the stretched sample.
Calculating GSM:
- Divide the sample weight (in grams) by the sample area (in square meters) for both relaxed and stretched states. This will give you two GSM values – one representing the relaxed state and the other representing the fabric under tension in a garment.
Additional Considerations:
- Sample Size: While 10cm x 10cm is a common size, some standards might specify a different sample area. Ensure you use the appropriate size for your chosen standard.
- Multiple Samples: For a more accurate representation, it’s recommended to take multiple fabric samples from different areas and average the resulting GSM values.
Calculating GSM for Woven Fabrics:
For woven fabrics, constructed from interlaced threads (warp and weft), calculating GSM involves a few steps:
- Sample Preparation: Cut a square-shaped fabric sample of a known size, typically 10cm x 10cm (or convert the area to square meters).
- Weighing the Sample: Use a precise weighing scale to determine the weight of the fabric sample in grams.
- Calculation: Divide the weight of the sample (in grams) by the sample area (in square meters) to obtain the GSM.
Formula: GSM = Sample Weight (grams) / Sample Area (square meters)
Example: If your 10cm x 10cm (0.01 m²) fabric sample weighs 5 grams, the GSM would be:
GSM = 5 grams / 0.01 m² = 500 GSM
Understanding GSM for Knit Fabrics:
Knit fabrics, formed by interlocking loops, can be slightly trickier for GSM calculations. Since knit fabrics can stretch, their GSM can vary depending on how the fabric is laid flat for measurement. Here are two approaches:
- Relaxed State GSM: Measure and weigh the fabric sample in its relaxed, unstretched state. This method provides a baseline GSM for the fabric.
- Stretched State GSM: Measure and weigh the fabric sample with a slight stretch that mimics how the fabric will behave in a garment. This value represents the GSM when the fabric is under tension in a garment.
Additional Considerations:
- Industry Standards: Certain types of fabrics, like denim or shirting fabrics, often have standard GSM ranges. Knowing these ranges can help you choose suitable fabrics for specific projects.
- Fabric Composition: The fiber content of a fabric can influence its weight. For example, a linen fabric with a high GSM might feel lighter than a polyester fabric with the same GSM.
The Importance of GSM:
Understanding GSM empowers you to make informed decisions when selecting fabrics for your projects. By considering the desired drape, weight, and functionality of your garment, you can choose fabrics with appropriate GSMs. This ensures your creations not only look great but also perform well based on their intended use.
In conclusion, GSM is a valuable tool for anyone working with textiles. By mastering the calculation for woven and knit fabrics, you can unlock a deeper understanding of fabric properties and make confident choices for your next sewing or design project. Here we learn more about GSM for Woven and Knit Fabrics.