Three spools of thread for leather, polyester, linen and nylon, on a workbench beside needles, beeswax and a stitched strip.
| |

Thread for Leather: Polyester, Nylon or Linen

ByPeter Joeseph 'Briefcase Maker' Kalafatis

Three fibers. One of them belongs on a machine. The other two are an argument.

Thread for leather comes down to three fibers, polyester, nylon and linen, and for hand stitching the choice gets made long before the first needle goes through, because the thread decides the size of the hole, the feel of the pull, how the ends get finished and what the seam looks like in twenty years. I hand saddle-stitch everything. I gave up sewing machines a long time ago. So everything here is about thread pulled by two hands through holes punched by hand, in the order the work happens, starting at the spool and ending at the last stitch.

Video: LINEN vs Polyester Threads for Stitching Leather, from Teran Atelier on YouTube.

That’s Teran Atelier, not my channel, putting linen and polyester side by side. Seeing the two threads in leather does more than a spec sheet. The spec sheets still matter, so here they are.

Picking the fiber for the job

Sun, water and stretch. Ask what the bag will live through.

Hands waxing thread for leather on a block of beeswax before saddle stitching.

Start with nylon, because it’s the easiest to rule in or out. Superior Threads, on its bonded thread page, says nylon is a little stronger than polyester, but that polyester has “a much better resistance to UV rays than nylon,” and it recommends bonded nylon for work that won’t sit in sunlight for long stretches. It names saddle, marine and automotive sewing as jobs often done in bonded polyester. A leatherworker.net member, mlapaglia, in a thread on nylon versus linen for hand stitching, moved off nylon for that reason and because it stretches as it ages. In another thread on bonded nylon and polyester, JJN puts it in seven words: nylon will stretch where polyester will not.

LeatherCraft Haven’s guide to leather thread is blunt about it: “Bonded nylon is primarily a sewing-machine thread”. My opinion is the same. A briefcase rides on a car seat in the sun and gets carried for decades. I wouldn’t hand-stitch one in nylon.

The machine people have their own reasons for liking it. In the bonded-thread discussion, CowboyBob says nylon’s stiffness helps on thicker leather, with fewer skipped stitches, and that polyester doesn’t make as good a loop for the machine needle to catch. Those are machine problems. A saddle stitch has no loop and no hook. Two needles pass each other in the same hole, and the thread never has to form a shape for a machine to grab, which takes away nylon’s best argument and leaves its worst ones.

Polyester is the default most suppliers point to. Rocky Mountain Leather Supply’s page for Ritza 25 Tiger thread describes a finely braided, flattened, lightly waxed polyester and claims strong UV resistance. Dictum lists the same thread as 16-ply braided polyester treated with synthetic wax.

Linen is the old answer. Coats’ Barbour linen datasheet lists saddlery and equestrian work among its uses, puts extension at break at about 2.5 percent, and says it gets stronger when wet. It also says, straight: “Resistant to ageing and moth attacks but sensitive to mildew growth.” The same sheet lists high moisture absorption. Flax is a plant. Keep it damp and dark long enough and it acts like one.

Color is the last call at this stage, and it isn’t only looks. A member named kgg says in that same bonded-thread thread that dye, black especially, changes how stiff a thread feels. Buy a short length of the color you want and stitch a scrap before you commit to a full spool.

Sizing the thread to the hole

The hole comes first. The thread has to fit what the chisel already did.

Thread sizes are a mess, because the three fibers are measured three ways. Polyester like Tiger is sold by diameter: RMLS lists 0.6, 0.8, 1.0 and 1.2 mm. Linen runs on old number systems. Gary Howell of GDH Leather Courses, in a post on hand-stitching threads, explains the Barbour-style count: “the lower the number, the thicker the thread,” with the ply after the slash, so 18/3 is three-ply. Sajou’s page for Fil au Chinois Lin Cable gives the French cable sizes with real diameters, from 332 at 0.77 mm down to 832 at 0.43 mm.

LeatherCraft Haven’s rule of thumb is that the thread should run about half the width of the chisel hole, so the stitch seats snug without straining the leather. That’s a good place to start on a scrap.

Then there’s my own hole. On my hand stitching page I wrote that hand stitching tends to have slightly bigger holes, because they’re punched by hand and sewn with hand needles: “The hand is limited to how small it can get, especially with thick bridle saddlery leather.” Thick bridle wants thicker thread. A fine thread in a big hole looks lost, and it lets the stitch roll.

Needles follow the thread. RMLS pairs Tiger with John James needles, from size 2 or 4 at 0.6 mm up to 2/0 or 3/0 at 1.2 mm. Howell suggests size 003 harness needles for beginners. Match them before you cut anything.

Cutting, waxing and threading

Wax is a tool. It holds the twist, it grips the hole, and it fights you a little.

Macro of polyester and linen saddle stitches side by side on bridle leather.

Cut generously. LeatherCraft Haven’s guide says to cut about four times the length of the seam, plus a margin. Running short three holes from the end of a gusset seam is a special kind of quiet.

Most leather threads come waxed, and the wax differs. Sajou’s linen goes through a bath of starch and beeswax, which the maker says leaves it smoother and slightly stiff. RMLS calls Tiger’s wax light and less gummy than heavily waxed threads. Weaver’s roundup of four hand-sewing threads says the wax on polyester adds weather resistance and a little stiffness, and suggests adding wax to linen as needed and giving the unwaxed Vinymo twisted polyester a light coat before hand stitching. Weaver also says linen has less body than Tiger, which can make it harder for a beginner to handle.

I wax my needles as well as the thread on heavy work. Through the thickest bridle I pull them with pliers, because fingers alone don’t get the needle through. Three layers of that leather, say a gusset, the body and a pocket, are hard on the hands in a way a thin wallet never is. That’s where thread choice stops being theory. In my view a thread that slips back in the hole between pulls costs you the stitch you just set, and on heavy work the wax is what stops it.

Then thread a needle on each end. Two needles, one thread, and the spool is behind you.

Pulling the stitch

Same pull on both needles, every hole. The thread tells you when you got it wrong.

My hand stitching page says that with each stitch the needles go into the hole, and skill is needed not to puncture the thread already sitting there, which a machine never has to worry about. That’s half of it. The other half is feel. Knowing when a strand has popped inside the layers is the skill, and you learn it in the fingers, not from a chart. My opinion: learn that feel on one thread before you switch fibers, because the signal changes with the thread.

Matt S, in a leatherworker.net thread on Barbour linen versus Tiger, says linen is much less slippery than synthetics, so the stitches lock better. Another member there, Avgvstvs, calls Tiger the most pleasant thread he’s used, because it’s only lightly waxed. Both can be true. Linen grabs. Polyester slides and then holds.

Pull hard enough to set the stitch into the leather, not so hard that it cuts the grain or puckers the line. Do it the same at every hole. The post on reading a stitch count covers what a buyer sees when the pull wanders. A seam that’s tight in one stretch and loose in the next tells everyone how the afternoon went.

Why the stitch matters at all is laid out in the post on why a broken stitch doesn’t sink a saddle-stitched seam. Each stitch locks on its own. That only holds if the thread can take the lock without stretching out of it, which is one more vote against nylon.

Finishing the ends, and the case for linen

Synthetic melts. Linen chars. That one fact decides more than people admit.

Finished hand-stitched leather briefcase handle with sealed thread ends beside pliers and needles.

RMLS says Tiger can be cut and melted back into the stitch hole for a clean finish. LeatherCraft Haven says polyester and nylon both heat-seal, but linen only chars, so a linen seam gets finished with a backstitch instead. Burning the ends is on my own channel, in finishing up the briefcase handle stitching by burning the thread ends, and that only works on a synthetic. The post on finishing a saddle stitch covers the backstitch and the burn in detail.

So far this reads like polyester wins. For a briefcase, in my opinion, it does: UV resistance, low stretch, an end you can seal with heat, and no mildew warning on the label.

Here’s where I have to give linen its due. Matt S makes the point in that thread that “stronger is not always better,” because stitching can be the deliberate weak point. My reading of it: when a seam fails, you want the thread to go, not the leather. Thread is cheap to replace. A torn panel isn’t. Linen also has the Barbour datasheet behind it for saddlery, low stretch, and a look polyester doesn’t quite match. Weaver calls it the choice for a refined, high-end look and says it takes on a patina with age.

And the mildew problem is a storage problem as much as a thread problem. A briefcase that lives in a dry office may never see enough damp to touch linen. So the honest version is this. I’d still stitch a briefcase in polyester. But a maker who stitches in waxed linen and finishes every seam with a careful backstitch isn’t cutting a corner. He’s choosing which part of the bag gets to break first, and that’s a decision a lot of polyester seams never had to think about.

RITZA Tiger Thread, Brown: A braided waxed polyester thread for hand-stitching leather. See it on Amazon (affiliate link).

Mandala Crafts Waxed Linen Thread: A spool of waxed linen thread for hand sewing. See it on Amazon (affiliate link).

Maine Thread .040" Brown Waxed Polycord: A spool of brown waxed polyester cord, .040 inch. See it on Amazon (affiliate link).

Beesworks Yellow Beeswax Bars, 6 oz: Yellow beeswax bars, 6 oz, for waxing thread. See it on Amazon (affiliate link).

John James Saddlers Harness Blunt Point Needles: A set of blunt-point harness needles, five sizes with five needles of each. See it on Amazon (affiliate link).

As an Amazon Associate I earn from qualifying purchases. A commission may be earned if you buy through this link, at no extra cost to you.

Sources

You Might Also Like

Similar Posts

Leave a Reply