Bag Sewing for Beginners: How To Make a Bag That Holds Its Shape

Bag sewing goes wrong at the materials counter, not at the machine. A bag holds its shape because of what sits behind the outer fabric, so the pattern matters far less than the layers you build underneath it. Get the interfacing and wadding right and an ordinary tote pattern stands up on its own. Get them wrong and the best pattern in the world sags by the time you have filled it.

There are four decisions that separate a homemade-looking bag from a professional one: the fabric you choose, the interfacing and wadding behind it, the thread and needle you topstitch with, and the hardware carrying the load. Almost every beginner guide covers the first one and skips the other three.

At a Glance

• Structure comes from the layers behind the fabric, not the pattern
• Match interfacing weight to fabric weight, not to bag size
• Wadding adds body and padding, interfacing stops stretch
• Topstitching needs heavier thread and a larger needle
• Hardware fails first at strap joins and base corners

What Actually Makes a Bag Hold Its Shape?

A bag panel is a stack, not a single piece of fabric. Outer fabric, interfacing fused to the back of it, an optional layer of wadding or foam, then the lining. Each layer does one job, and leaving one out shows in the finished bag.

Interfacing stops the fabric moving. It bonds to the back of the outer panel and takes the stretch out, which is what keeps the top edge from gaping and the sides from bowing once the bag has weight in it.

Wadding does something different. It adds thickness and softness, so the bag has body and the corners sit square rather than creasing flat. A tote made with interfacing alone will stand up but feel thin. Add wadding and it feels like something you bought.

The lining is the layer most beginners treat as decoration. It also holds the shape from the inside, which is why lining fabric worth supporting should be interfaced too.

The four layers inside a bag panel, and the job each one does.

Which Fabric Should You Choose for Your Bag?

Choose the fabric by how the bag will be carried and how much weight it will hold, not by how it looks on the bolt.

Quilting cotton is a perfectly good choice for a first bag, which is not what most guides tell you. The catch is that it does nothing structural on its own, so every piece needs interfacing behind it. Skip that step and you have made a fabric envelope.

Heavier fabrics work the other way round. Canvas and denim already hold their shape, so they need less support underneath, and over-interfacing them makes a bag that is stiff to sew and awkward to turn through. Our dress fabrics range covers most weights you would use for a bag body, and the upholstery fabrics are worth a look for anything that needs to take real punishment.

Beginners also lose bags to the wrong fabric entirely rather than the wrong weight, and which fabrics to avoid when learning to sew covers the ones that will fight you at the machine.

Which Interfacing and Wadding Do You Need?

For a first bag: medium-weight fusible interfacing on every outer and lining piece, and wadding only where you want thickness. That covers most totes and project bags.

Fusible or sew-in. Fusible irons on and holds the fabric flat while you work, which is why it suits beginners. Sew-in interlining is for fabrics that will not take iron heat, such as faux leather and some coated cottons, where fusing melts the surface. Check the fabric before you reach for the iron.

Woven or non-woven. Woven interfacing has a grain and behaves like the fabric it is bonded to, so it moves naturally and gives a softer, more professional result. Non-woven has no grain, costs less and is fine for smaller pieces such as pockets and straps, though it can crease along fold lines over time. For a bag body, fusible woven interlining is the safer choice. Vlieseline's own product reference lists the weight of each code if you want to match precisely.

Wadding. Quilters Choice wadding is what gives a bag padded body and square corners. It goes in after the interfacing, not instead of it. The two are not interchangeable: interfacing stops stretch, wadding adds thickness.

Two rules that fix most first attempts:

• Trim wadding back to the stitching line, not the raw edge. Left in the seam allowance it bulks the corners and stops them turning cleanly.
• Press, do not iron. Lift and lower the iron rather than sliding it. Sliding drags the interfacing out of position before the adhesive grabs, which is where bubbling comes from.

Why wadding is trimmed back before the corner is turned.

Why Bag Sewing Needs Heavier Thread and a Bigger Needle

The numbering catches people out: the lower the number, the thicker the thread. Gütermann's TERA range runs from TERA 40, which is tkt 40, tex 75 high tenacity continuous filament thread on 1200m cones, up through TERA 30 and TERA 20, which get progressively heavier.

For a first bag on a domestic machine, TERA 40 is the one to start with. The recommended needle size for it is NM 90 to 110, so a 90/14 for lighter fabrics and a 100/16 or 110/18 once you are into canvas and denim. TERA 30 and TERA 20 are heavier again and better suited to a machine built for the work, so leave those until you know your machine will take them.

Match the needle to the fabric as well as the thread. A jeans or denim needle has a stronger shaft and a sharp point that gets through layered canvas without deflecting, which is what causes skipped stitches when a universal needle is asked to do too much. SCHMETZ's own needle guidance sets out which point suits which fabric.

Three settings changes that make topstitching look deliberate rather than accidental:

• Lengthen the stitch to around 3mm to 3.5mm so the heavier thread reads as a line
• Use the heavy thread on top only and standard thread in the bobbin, which keeps tension manageable on a domestic machine
• Sew a test seam through the same number of layers you will hit at the corners, since that is where the machine will complain first

If your machine skips stitches once the layers build up, our guide to skipped stitches works through the usual causes.

Which Bag Making Hardware Should You Use?

Choose hardware by where the load goes. Bags fail at three points: the strap join, the base corners, and the closure.

Straps. The strap join takes the entire weight of the bag, and stitching alone will eventually pull through. Rivets set through the strap and the bag body spread that load and are the single biggest upgrade to a first bag. Use eyelets where a strap threads through or adjusts, and where a drawstring passes through the top edge.

Base and corners. These wear before anything else, particularly on a shopper that gets set down on pavements. Rivets at the base corners, or a doubled base panel with an extra layer of interfacing, will add years.

Closures. Jeans buttons give a flat, secure closure that sits well on canvas and denim. Press fasteners suit lighter bags and quick access. Use a zip where the contents matter, and pick the weight to match the bag rather than the other way round.

Your Bag Making Supplies Checklist

Work down this list before you cut anything. Missing one line is what sends people back to the shop halfway through a project.

If you want to feel the weights before committing, the counters at Franklins Group stores will let you compare interfacing against your chosen fabric.