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Short answer
Grain is the direction of the threads in a woven fabric. The straight grain runs along the roll, parallel to the selvedge; the cross grain runs across it; the bias runs at 45 degrees and stretches the most. Curtains and upholstery are cut on grain so they hang straight, while piping is cut on the bias so it bends smoothly round curves.
What are straight grain, cross grain and bias?
| Direction | Runs | Behaviour | Used for |
|---|---|---|---|
| Straight grain (warp) | Along the roll, parallel to the selvedge | Strongest; least stretch | Most curtains and upholstery panels |
| Cross grain (weft) | Across the roll | A little more give | Railroaded curtains and long sofa backs |
| Bias | At 45 degrees | Stretches and drapes most | Piping, bindings, curved edges |
Why do curtains need to be cut on grain?
A curtain cut off grain twists and hangs crooked, its hem drops unevenly, and stripes or checks lean. Curtain makers cut along a thread line, or square the fabric to the pattern, so each drop hangs straight. See How to Hang Curtains.
What are bow and skew?
Sometimes the cross threads are not at right angles to the selvedge, from tension during weaving or finishing.
- Bow: the cross threads curve, like a smile or frown across the width.
- Skew: the cross threads run on a slant from one selvedge to the other.
- Why it matters: on plains it is hard to see; on stripes, checks and patterns, the design looks crooked when the fabric is cut straight.
Tip
On patterned fabric, check that the pattern runs square to the selvedge before cutting. Your curtain maker will cut to the pattern, not the edge, where they differ. See Check, Stripe and Plaid Curtains.
Why is piping cut on the bias?
Bias-cut strips stretch and bend smoothly round curved cushion corners and seat edges without puckering. That is why piping and edge bindings are cut at 45 degrees. See Cushion Fabric Guide.
Frequently asked questions
What is fabric grain?
The direction of the threads in a woven fabric: straight grain along the roll, cross grain across it.
What does cutting on the bias mean?
Cutting at 45 degrees to the grain, where the fabric stretches and drapes most.
Why does my striped curtain look crooked?
The fabric may be skewed or bowed, or cut off grain. Patterns should be cut square to the design.
Why is piping cut on the bias?
Bias strips stretch, so they bend smoothly round curves without puckering.
Curtain maker, upholsterer or designer?
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