Fabric Types, Grain and Shrinkage Awareness
What the exam tests
Identifying fabric structure and grain, predicting shrinkage and behaviour, and choosing the right needle and handling for each fabric.
Fabric groups
Woven fabrics have lengthwise (warp) and crosswise (weft) threads; lengthwise grain runs parallel to the selvedge, is strong and stable, and is the grainline for pattern layout. Crosswise grain has slight stretch; true bias at 45 degrees stretches most. Knits are interlocking loops and stretch crosswise. Natural fibres are cotton, linen, silk and wool; synthetics include polyester and nylon; rayon is semi-synthetic.
Behaviour and shrinkage
Cotton may shrink 3-5% on the first wash, linen more; wool felts with heat and friction; synthetics shrink little but can melt under a hot iron. Pre-shrink washable fabric before cutting, or add a shrinkage allowance. Check drape, fraying and nap. Corduroy, velvet and satin have direction; cut all pieces the same way.
Needle and thread
Fine fabric 9/11 needle and 60s thread; medium cotton 14 and 40s; denim 16; knits a ballpoint or stretch needle. Match thread to fibre where possible.
Worked example
A pattern needs 1.90 m of cotton and the shop has 2 m. Reasoning: 5% shrinkage of 1.90 m is about 0.10 m, so usable length is only 1.80 m. Buy 2.10 m or pre-wash the fabric before layout.
Traps
Assuming all cotton shrinks the same; ignoring nap direction; cutting knits on the stable grain and losing stretch; using a sharp needle on jersey and causing ladders; ironing polyester at cotton temperature.