Twill is a type of woven fabric. It’s not a fiber or yarn type.
The fabric is woven in such a way – the weft going over two threads and then under one, or some other ‘unbalanced’ combination – as to create a distinct ‘diagonal’ ridged pattern on the surface of the fabric. Because of this weaving technique, twill can drape better than a plain woven fabric – one where the weft goes over and under an equal number of warp threads each time.
Twills may be made from any fiber you like, but are most often made from cotton and cotton-polyester blends. The most well-known example is denim, which is a cotton twill. Another well-known twill weave is gabardine, which can be made from wool, wool-poly or a number of other fibers – although it’s most often associated with wool suiting.
Twills can vary from light weight to heavy weight but you’ll most often find them in medium and heavy weights. You’ll find twills used for shirts, pants, suits and coats – all depending on the exact fibers used and the weight of the fabric.
I’ve used cotton twill to add weight to lighter fabrics via the interlining technique. That’s was very handy when I wanted to make a substantial looking overcoat for a costume, but all I had was very light cotton velveteen.
It can sometimes be hard to tell, but twills do have a wrong side and a right side and it does matter – you should use the ‘with nap‘ layout when cutting. Just keep looking and you’ll see it. If totally confused, ask the salesperson at your local fabric store to show it to you on the bolt – and when you buy it, be sure to mark it with chalk.
The washability and utility of a twill depends on the fiber it’s made from. Cottons shrink, but polyester won’t. Pay attention to the bolt end or do a burn test if you’re uncertain about its composition. Some seamsters like to run 100% cotton twill through the wash twice to make sure that the fabric has done all the shrinking it’s going to do.
Twills can show wear over time, and become shiny and flat as the texture is crushed down. Grab a pair of really old jeans that you’ve worn a lot and take a look at the seat. It probably won’t be a factor in a costume you’re going to wear only a few times a year, but it’s something to be aware of.
Cotton twill can go into a dryer on high heat, and cotton/poly twill can be dried on medium or low heat. A wool or wool-poly gabardine should be handled more carefully as wool demands your respect – wash it in cold water and lay flat to dry or, if it’s a wool-poly blend, you can tumble it on low, but pull it out promptly. Cotton twills can be ironed at a high temperature with steam, and blends at medium heat.
If the seams are really thick, you’ll want a little extra help when pressing in the form of a clapper – a smooth piece of shaped wood – that’ll help put a bit of extra pressure on any seams WITHOUT putting your fingers in range of the iron. If I had a dollar for every time I steam-burned my fingers with my iron, I’d have at least twenty bucks.
Depending on the project and the fabric, you might want to use the “with nap” layout when getting ready to cut your pieces. Some twills, the direction barely shows, in others, it’s pretty obvious, so be careful.
There are jeans/denim specific needles out there, which are appropriate for sewing twill. If your fabric is heavier weight, then use a heavier needle. All purpose thread and a regular straight-stitch is fine, although you’ll want to use a slightly longer stitch for heavier-weight twills. A roller foot for bulky seams will come in very handy. If you’re sewing stuff that’s very heavy, be careful, ask your sewing chums if they have an older “gear-driven” machine – rather than modern belt-driven machines – that are better able to sew heavy-weight denim.