Know before you sew: best fusible interfacing for bags

There are SO many bags we want to sew—do you feel the same?

Bags from
Big-City Bags, Windy City Bags, and Style and Swing

With the right pattern, you can sew anything from backpacks and suitcases to purses, clutches, and handbags that rival designer bags from department stores. (And better still, you can sew them with your favorite quilting fabrics!) But there’s one thing you’ll need before you sew: a little know-how. So today we’re shedding light on what some might see as a bag-making mystery: how to choose the best fusible interfacing for bags.

Author Sara Lawson is a rock-star in the sew-your-own-bags world—she’s passionate about her craft and she’s worked hard to make it easy for you to sew beautiful bags with body and structure, with all the retail details the bags from your favorite shops have. Today we’re sharing an excerpt from her latest book, Windy City Bags, that will introduce you to which fusible interfacings do what, and why they’re Sara’s favorites.

Save 40% when you order any of these three bag-making books today (and as always, earn free shipping to the US and Canada when you spend $40 or more):

Save 40% on select bag books

Create bags that will turn heads and invite the question: where did you get that bag? Won’t they be surprised when you tell them you made it yourself!

Sara LawsonOne of my favorite topics is interfacing; you really can’t make a bag without it. Interfacing makes up 25% of my fabric stash . . . no lie! It’s one of those things that you just need to have on hand at all times, because you’ll use it in almost every project.

Most of my favorite interfacings are fusible. When fusing interfacing to your fabric, always use a pressing cloth to protect the fabric from excessive heat and keep the adhesive off your iron. Always place the bumpy or tacky side of the interfacing against the wrong side of the fabric.


I absolutely love Thermolam Plus, a needled fleece that is denser and flatter than generic fusible fleece. When I’m making a bag or other accessory, I like it to have body; even for a simple tote bag, just two layers of fabric is too thin for me. This is a matter of personal preference, but I want my bags to have some substance and to be able to carry 20 pounds without tearing at the bottom. I use Thermolam Plus fused to the bag’s exterior fabric, sometimes in combination with either Shape-Flex or fusible fleece fused to the bag’s lining fabric.

Thermolam Plus, once fused, leaves the fabric looking nice and smooth. Test a small piece on your exterior fabric. Depending on your iron, you may need to apply heat longer than the manufacturer recommends, but be careful not to damage the fabric. Sometimes I leave the iron in place up to double the recommended time.

Festival Bag
Festival Bag from
Windy City Bags


I use Shape-Flex, a fusible woven interfacing, in all of my bags. It’s the most important interfacing in my stash, and I rely on it for a variety of uses. I fuse woven interfacing to every pocket I make, and I use it to reinforce the area around a zipper.

Once fused, Shape-Flex gives quilting-weight cotton the sturdy feel of a home-decor or canvas-weight fabric. Place the rough, tacky side against the fabric’s wrong side for fusing. Shape-Flex is perfect as a stand-alone interfacing in a pouch or other small project, or you can combine it with other interfacings.

Trendy Hipster Bag
Trendy Hipster Bag from
Style and Swing


This stiff interfacing is good for adding firm body without too much thickness. Because it’s a sew-in interfacing, it won’t fuse to your fabric. You can baste the interfacing to the fabric ⅛" inside the seam allowance, but I prefer this alternate method: Cut one piece each of Shape-Flex and Peltex Sew-In the same size as the pattern piece. Trim ½" from the edges of the Peltex Sew-In. Center the Peltex Sew-In on the wrong side of the fabric and then place the Shape-Flex on top with its fusible side down. When you fuse the Shape-Flex, it will seal the Peltex Sew-In to the fabric along the ½" edges. Using a smaller piece of Peltex Sew-In also reduces the bulk of the seam allowance.

Wonderland bag
Wonderland Bag from
Big-City Bags


When there are bag panels or handles that need to look stiff without crinkling at folds and creases, this is the interfacing to use. My favorite application is to use this interfacing in two layers. First, I fuse a layer of Shape-Flex against the wrong side of my fabric, and then I add two layers of Décor Bond, cutting the Décor Bond ½" smaller on all its edges to keep bulk out of the seam allowances. One or two layers of Décor Bond will help a bag stand up by itself, but without quite as much stiffness as you’ll get with Peltex Sew-In.

Jump-Start Duffel Bag
Jump-Start Duffel from
Windy City Bags

There are no hard-and-fast rules for using interfacing. I suggest that the best way to learn more about interfacing is to use it in all of your projects. Tweak your interfacing choice based on your personal preference: what kind of shape are you interested in, how much stiffness, what kind of body? There are unlimited possibilities!

Find all the bag-making know-how you need (along with Sara’s favorite interfacing of all) in Sara’s books. And take advantage of these three books on sale today—it’s the perfect time to start stitching a special bag for summer fun!

Windy City Bags Style and Swing Big-City Bags

What kind of a bag maker are you?

  • I’m a beginner and excited to try.
  • I’ve sewn a few and I want to sew more.
  • It’s an obsession—you can never have too many bags!

Tell us in the comments!









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