Fabric, Grainlines, Seam Allowances, and Cutting Basics

Woven fabric is constructed by interlacing two sets of threads at right angles: • Lengthwise Grain (Warp): Threads running parallel to the finished woven borders (the selvages). This is the strongest, most stable grainline with the least amount of mechanical give. Garment center fronts, center backs, and trouser legs are cut on the lengthwise grain so they hold their shape over time. • Crosswise Grain (Weft): Threads running perpendicularly from selvage to selvage. Slightly softer with gentle give. • True Bias: A precise 45-degree angle across the warp and weft. At this angle, the woven grid deforms elastically, offering maximum stretch, fluid draping, and contouring ability. Bias tape is cut at this exact angle so it can bend smoothly around curved necklines and armholes without buckling.

Natural fibers (linen, cotton, wool, silk, rayon) undergo dimensional change when submerged in water and heat. Unwashed linen can shrink between 5% and 10% in its first washing, which can reduce a fitted top by a full size. • Wash and dry your fabric using the exact laundry methods you intend to use for the finished garment. • If making a linen or cotton blouse, machine wash warm and machine dry completely. • Press the fabric thoroughly with steam before laying it out on your cutting table. Wrinkles distort pattern pieces and create inaccurate cut lines.

Fabric often dries off-grain or is wound onto commercial bolts crookedly. To restore true right angles: 1. Snip into the selvage and gently pull a single crosswise thread all the way across the width of the fabric. Cut along the thread path to create a perfectly straight edge. 2. Fold the fabric in half lengthwise, bringing the two selvages together along the table edge. 3. The crosswise cut ends should align squarely. If the fabric ripples or twists when selvages are aligned, the grain is distorted. Gently pull opposite diagonal corners of the fabric to pull the yarns back into a square 90-degree grid.

Every sewing pattern indicates whether seam allowances are included or must be added manually. All Threadline patterns include explicit seam allowances directly on the pattern lines. • Standard Construction Seams: 1.5 cm (5/8") on shoulder and side seams. This generous allowance allows for French seams, flat-felled seams, or future fitting alterations. • Narrow Clean-Finish Seams: 6 mm to 10 mm (1/4" to 3/8") for bias binding, collars, and neckbands where bulk must be avoided. • Hem Allowances: 1.5 cm for baby hems, or 3 cm to 4 cm for deep tailored hems. Always maintain the exact specified seam allowance when sewing. Straying by just 3 mm on four vertical seams alters the total garment circumference by 2.4 cm (almost an entire inch).

For clean, precise cuts: • Keep fabric resting flat on your cutting mat or table; never lift the cloth into the air while cutting with shears. • Use pattern weights (washers, river stones, or dedicated weights) rather than excessive pinning, which causes buckling. • Notches: When cutting out pieces, snip 3 mm (1/8") directly into the center of each triangle notch mark. Never cut deeper than half the seam allowance! Alternatively, cut triangular notches pointing outward beyond the cutting line for fool-proof safety.