Cotton Thread

Which Cotton Thread Weight for Which Job

Cotton thread is what most quilters piece with, and the reason is simple: it behaves like the fabric it is sewing. Quilting cotton and cotton thread shrink at a similar rate, press flat under the same iron, and age at the same pace, so a seam sewn in cotton stays as flat in ten years as it was on the day it was pressed.

The decision that actually matters is weight. Thread weight counts backwards, so a higher number means a finer thread. Everything else on this page follows from that one number.

40, 50, 60 and 80 Weight, and What Each One Is For

A 50 weight cotton is the default for piecing and the thread most quilters keep on the shelf in white, cream and grey. It is fine enough to make a flat seam and strong enough that nobody thinks about it.

A 40 weight is heavier and is for quilting you want to see. Feathers, ruler work, dense fills and anything meant to read as a design belong here, because a heavier thread sits up on the surface of the quilt instead of sinking into it.

A 60 weight is finer than 50 and earns its place where seam bulk is the problem: appliqué, English paper piecing, and blocks where six or eight seams meet at a single point. A 80 weight is finer still and is for invisible work, machine appliqué and very small piecing.

If you are only buying one, buy a 50. If you are buying two, buy a 50 for piecing and a 40 for quilting, and you have covered most of what a quilt needs. Our piecing thread and quilting thread and bobbins collections split the range by job rather than by fiber.

Two Ply or Three Ply, and Why Anyone Cares

Thread weight tells you how fine the finished thread is. Ply tells you how it got there.

A two-ply 50 weight twists two strands together. A three-ply 50 weight twists three finer strands to the same finished thickness, which takes a tighter twist and generally produces a stronger thread at the same weight. Aurifil's 50 weight Mako is the best known two-ply. YLI Dream Seam is a three-ply at the same weight, which is unusual and is the reason it exists.

In practice both piece beautifully and the difference shows up at the extremes: long seams under tension, foundation paper piecing where thread gets stitched through paper and then torn, and anything that will be unpicked and re-sewn.

Cotton or Polyester

This argument is older than any of us and both sides are partly right.

Cotton is softer, presses flatter, produces a more traditional finish, and will not outlast the fabric around it. That last point matters more than it sounds. A thread stronger than the fabric can cut through it over decades of washing, which is the case against polyester in an heirloom quilt.

Polyester is stronger, stretches slightly, resists abrasion better and comes in finishes cotton cannot match. For a quilt that will be washed weekly by a family with a dog, that strength is a feature rather than a risk.

The honest answer is that for a quilt meant to be used, either works and the choice is about finish. For a quilt meant to be kept, cotton is the safer bet.

Lint, and Why Some Cotton Threads Make So Much Less of It

All cotton thread sheds. The amount depends on two things the manufacturer did before it reached you.

Staple length is the first. Extra-long staple cotton, whether it is called Egyptian, Giza, Pima or Supima, is spun from longer fibers with fewer ends to work loose. Short staple cotton sheds more, and it is the reason a cheap thread fills a bobbin case in an afternoon.

Gassing is the second. Running the thread through a flame burns the surface fuzz off, and threads that are gassed twice leave noticeably less behind. Mercerizing, which is a caustic bath under tension, is what gives cotton its sheen and its dye uptake, and it is why a good cotton thread reads as a richer color than a cheap one.

None of it removes the need to clean under the bobbin case. It changes how often.

Shop Cotton Thread at Quilted Joy

Quilted Joy is a destination quilt shop and skill-building studio in Louisville, Kentucky, serving quilters in our shop and across the country.

We carry Aurifil, Mettler, YLI, and Riley Blake's Confetti Cotton, plus perle cotton for big stitch hand quilting and prewound bobbins so the bottom of the quilt is sorted at the same time as the top.

If you are choosing thread against a specific fabric, the Quilt Fairies will hold spools next to it in daylight, which is the one thing a screen cannot do. Bring the fabric, the block, or a photograph.

Frequently Asked Questions About Cotton Thread

What weight cotton thread is best for piecing?

A 50 weight. It is fine enough to keep seam allowances flat and strong enough for every seam in a quilt top, which is why it is the standard piecing weight across nearly every cotton thread line.

Drop to a 60 weight if you are piecing very small blocks or doing appliqué, where the extra fineness keeps intersections from building up bulk.

What is the difference between 40, 50 and 60 weight thread?

Thickness, and the numbering runs backwards. A 40 weight is the thickest of the three, a 60 the finest.

Use a 40 for quilting you want to be visible, a 50 for general piecing and quilting, and a 60 for appliqué, dense piecing and anywhere seam bulk is a problem.

Is three-ply cotton thread better than two-ply?

Not better, but different, and it is generally stronger at the same weight. Three finer strands twisted tightly give more strength without more thickness.

Two-ply threads are the more common piecing standard and piece perfectly well. Where three-ply earns its keep is foundation paper piecing, long seams and anything you expect to unpick.

Should I use cotton or polyester thread for quilting?

Cotton if the quilt is meant to last generations, because cotton thread will not outlive the fabric and cut through it. Polyester if the quilt will be used hard and washed constantly, because it is stronger and more abrasion resistant.

For most quilts either is fine and the real difference is finish. Cotton presses flatter and looks more traditional.

Does cotton thread break more easily than polyester?

It is less elastic, so it tolerates less stretch before it gives. That shows up as breakage more often on a longarm at speed than on a domestic machine piecing at a normal pace.

Most breakage blamed on thread is actually a burred needle, a needle too small for the thread, or top tension set too tight. Change the needle first.

What needle should I use with cotton thread?

An 80/12 for 50 weight piecing, and a 90/14 for 40 weight quilting. Drop to a 70/10 or 80/12 microtex for 60 weight and finer.

The rule behind the rule: the eye of the needle has to be big enough for the thread to pass without abrading, and the hole it makes has to be small enough not to show. Fine thread, fine needle.

Why does my machine fill with lint when I use cotton thread?

Some of it is unavoidable, since cotton is a staple fiber and staple fibers shed. The amount varies enormously with quality. Extra-long staple cotton that has been double gassed sheds a fraction of what a short staple thread does.

Batting contributes at least as much as thread does, so a quilt that is throwing lint may be the batting talking rather than the spool.

Can I use cotton thread in the bobbin?

Yes, and matching the top and bobbin thread is the simplest way to keep tension predictable, because both sides then behave the same way.

Some quilters use a finer thread in the bobbin to reduce bulk on the back. That works, but it is a deliberate choice, not a default, and it needs a tension check on a sample first.

Do the top and bobbin threads have to match in color?

No, and on a quilt they frequently should not. Matching the bobbin thread to the backing rather than the top is what makes quilting recede into the back of the quilt.

Where they do need to agree is weight. Two threads of very different weights top and bottom will fight the tension setting.

Can Quilted Joy help me choose a thread?

Yes, and it is worth asking rather than guessing from a screen. Tell a Quilt Fairy what you are sewing, whether it is piecing or quilting, and what machine it is going on, and we will narrow several hundred spools down to two or three.

If you are matching a specific fabric, bring it in or send a photo. Thread reads differently on a spool than it does in a seam, and comparing them side by side takes a minute.