Basics

The right thread: material, weight and colour

Polyester or cotton, fine or heavy, lighter or darker? How to pick a thread that suits your fabric, holds up and stays out of sight where it should.

On the left a petrol-coloured fabric with two threads laid on it: the lighter one stands out (wrong), the slightly darker one almost disappears (right). On the right a patterned fabric on which a thread in the background tone and a beige-grey thread barely show (both right).

Thread is the cheapest part of your project, and yet it holds everything together. The wrong thread breaks, sheds lint, stands out in colour or pops as soon as the fabric gives.

The good news: one thread covers almost everything, all-purpose polyester sewing thread. Here's when to choose something else, what the number on the label means, which colour to pick and how to recognise good thread. Which needle goes with it is explained in The right needle for every fabric.

What you need

All-purpose polyester sewing thread
A scrap of your fabric
Daylight for comparing colours
For visible topstitching: topstitching thread and a matching needle
A tin or drawer for your spools

Step 1

The default: all-purpose polyester thread

A large spool whose thread leads into two seams: at the top a zigzag seam in jersey that is being stretched and holds, at the bottom a straight seam in woven fabric.

If you only buy one thread, make it this one. All-purpose polyester thread is strong, smooth and has a tiny bit of give. That's exactly what a seam needs when it gets pulled and stretched as you wear it.

It suits almost every fabric: cotton, linen, viscose, blends and jersey too.
It handles the washing machine and dryer, doesn't shrink and hardly fades.
It comes in a huge range of colours.

For the Hanne jersey trousers and the Merle top it's the right choice. To keep a jersey seam from popping, the stitch matters too, more on that in 5 jersey traps.

Step 2

Cotton thread: lovely on natural wovens, but not for jersey

On the left, right: cotton thread with a straight seam in woven fabric. On the right, wrong: jersey is pulled sideways and the cotton thread seam has broken in the middle.

Cotton thread is matt and soft and looks good on cotton and linen. But it has almost no give. When the fabric stretches, the seam breaks.

Cotton thread is worth it when …

you're sewing natural-fibre wovens that don't get stretched, such as cotton or linen,
you want to dye the finished piece: cotton thread takes the dye along with the fabric, polyester stays light,
you're doing fine handwork, such as hand stitches, basting or delicate batiste lingerie.

It isn't suitable for jersey or any seam that has to stretch. And if you don't want to decide: polyester thread works perfectly well on cotton fabric too.

Step 3

Heavy topstitching thread and other special threads

Three panels: a spool of heavy thread and a double row of bold topstitching along the edge of a firm fabric; a spool of fluffy woolly nylon and soft loops along the edge of a knit; a clear spool and a barely visible seam on patterned fabric.

Topstitching thread is much thicker and makes topstitching stand out, for example on bags, jeans or the Kirsche wallet in cotton fabric. To make it work:

Use a larger needle with a big eye, a topstitching or denim needle in size 90 to 100. More on that in The right needle for every fabric.
Put regular all-purpose thread in a matching colour in the bobbin.
Set a longer stitch, about 3 to 3.5 mm, and test the thread tension on a scrap first.

Less often you'll need woolly nylon, a soft, stretchy thread for the overlocker loopers or for soft hems on knits, and invisible thread made of nylon. It's see-through, but it can scratch and can't take a hot iron.

Step 4

Reading the label: what the number means

Two spools, one finely and one coarsely wound. A thread runs from each onto a white card, and a magnifying glass shows the thin and the thick thread enlarged. Below, a fabric scrap with a fine and a bold test seam.

The spool usually tells you the material, the length in metres and a number for the weight. For many threads: the higher the number, the finer the thread. All-purpose thread is often labelled 100 or 120, heavy topstitching thread more like 30 or 40.

Unfortunately there are several systems. If it says “tex”, for example, it's the other way round, and a higher number means thicker thread. And the same number from two makers isn't always the same thickness.

So don't rely on the number alone:

Pull a length off two spools and lay the threads side by side.
Sew a few centimetres on a scrap of your fabric, with the needle you plan to use.

Step 5

Colour: a shade darker is safer

Choose the colour that appears most on your fabric. If you can't find an exact match, go a shade darker. A single thread looks lighter on the fabric than on the spool. A slightly darker seam hardly shows, a lighter one does.

Compare in daylight and lay a pulled-off thread on the fabric, not the whole spool.
For printed fabrics, take the background colour or the colour that appears most. On colourful prints, grey and beige tones often disappear best.
Use contrast thread on purpose when the topstitching is meant to be a feature.
If only the top side shows, the bobbin can hold a neutral, similar tone.

Step 6

Quality and storage: the thread has to hold

On the left, wrong: a faded spool sits on a shelf in the sunlight by a window, below it a thread that snapped when pulled apart. On the right, right: brightly coloured spools in a tin with a lid, below it a thread that holds when pulled.

Cheap thread is often uneven and hairy. It frays at the needle eye, breaks in the middle of a seam and leaves a lot of lint under the needle plate. Saving money here hardly pays off, since you only need a little of it.

Good thread ages too. If it sits on a sunny shelf for a long time, it becomes brittle and fades. Do the pull test: pull a length of thread firmly between your hands. Good thread gives a little and holds. If it snaps straight away with a quiet crack, don't use it for seams that need to hold any more.

Keep your spools dark and dust-free, for example in a tin or a drawer.