What is sew-in interfacing? Sew-in interfacing can be anything you sew between the layers of your project to provide structure. You can specifically buy sew-in interfacings in various thicknesses and stiffnesses or you could use canvas, muslin or cotton batting.
If I can’t fuse it, how do I attach it? Both fusible and sew-in interfacing should definitely be sewn into the seams. Even though I cut my fusibles smaller than the fabric, I always leave enough to make sure it’s caught in the stitching line. If you are *really* close, and will top-stich that seam and will catch it in the top-stitch, that’s OK too. With sew-in interfacing you have to be sure that it gets stitched into the seam or it will come apart when you turn the project. What I do is cut the sew-in the same size as the fabric, which makes it easy to line up, and pin around the edges and in the middle if it won’t harm the fabric. You can alternatively use binder clips (either the paper-holding or quilting kind) if you don’t want to pin. THEN, as soon as I’m done stitching, I take my sharpest little embroidery scissors and trim off any excess interfacing. What is excess? It depends on the project. Sometimes you want stiffer interfacing to remain in the seams to create a kind of boning, especially on outside curves. On the Sammy Bag, I trim the batting but leave the interfacing. For flat pockets or soft interfacing/batting/canvas where it’s not providing any structure, or in cases where the machine will have trouble sewing through a gazillion layers, I get rid of it. It helps to have less bulk when pressing seams open and when sewing multiple layers together when assembling the final project.
Why use fusible interfacing? Sew-ins can be a bit more of a hassle to work with than fusibles because you have to pin them and you have more layers to keep track of. I think they are worth the hassle. I like them because they can give a more natural shape to the finished project, they wrinkle less and the extra bulk can be easily trimmed from seams. I typically layer sew-ins with lightweight or midweight fusible interfacing. If you use cotton fabric with just a sew-in and no fusible at all, the outside might look floppy or loose while the overall project will have structure, but it depends on the project. Typically, when I need to add more bulk than a couple layers of fusible SF101 can add (fused to the outside and lining), I add a layer of sew-in interfacing rather than using a thicker or stiffer fusible.
Which interfacing should I choose? You have to decide basically two things – How much structure and stiffness you want your project to have, like do you want your bag to stand up on it’s own? and if you are looking for a puffy look or not. If you want that quilted, stands-up-empty bag look, then you would actually use a combination of fusible, sew-in and batting. The nice thing is that in contrast to fusibles, the Pellon sew-in numbering system makes sense. The higher the number, the stiffer the interfacing. Just like fusibles, a lot of this is experimentation and personal preference.
Pellon 30 – Lightweight non-woven. Made out of a similar material as the Pellon Fusible Midweight Keep in mind that the actual GLUE in fusibles adds a bit of stiffness, even if the material is the same, so you tend to want to go up a weight in sew-in. Although the 30 actually feels like the same paper backing used in Fusible Midweight. Pellon 30, 40 and 50 are all of similar thickness, but the 30 is certainly the softest and floppiest.
Pellon 40 – Medium weight non-woven. Comparable to fusible mid-weight. I would use this or Pellon 50 in the same function. This would be good for pairing with fusibles. Both 30 & 40 would be good for wallets, sling/hipster purses and things that don’t have to stand up on their own.
Pellon 50 – Almost-heavyweight, non-woven. Pellon 50 is very common and pretty popular. Use this for fabric baskets/buckets/boxes, wide bags that need to stand up empty, wallets that need stiffness, or pair it with batting/fleece to give structure and softness. Compare this one to Decor Bond, without the wrinkling!
Pellon 70 “Peltex” – Heavyweight sew-in. Sometimes you will see “Timtex” in a pattern, but Peltex is similar and easier to find. Peltex is heavy-duty. It kind of resembles very stiff craft felt. Maybe think of it as fabric cardboard. When you look at the product alone it is softer than you would expect, but once you get it in your project and top-stitch, it’s very sturdy. It comes in fusible versions as well (71F is one-sided fusible, 72F is two-sided fusible) but I prefer the sew-in version. Fusing it would give your project an unnaturally stiff look. I use it for bag bottoms and for flat projects like these notepads. Ideally, it is added at the end of the project either as a bag bottom or before closing up a seam. Sometimes it is cut to fit inside seam allowances and then covered with a thin piece of fusible interfacing to keep it against your fabric. You can easily sew through it to top-stitch, you don’t want to stitch and turn it if you can avoid it because it will make your seams look very bulky and unprofessional.
Another thing I’ve used for bag bottoms sometimes is plastic canvas from the cross-stitch aisle. You cannot sew though this! But you can make a sleeve for it and place it into the bottom of your bag.
Pellon 988 – Fusible Fleece minus the fuse. This is a very thin, lightweight poly batting. It’s really not enough to give structure but it will add a bit of softness to your project. Be careful, it stretches. It is certainly not as stiff as the fusible version, since the glue in the fusible adds a degree of stiffness. If you want this to perform similarly to 987F, pair it with a fusible or another sew-in, even if you are quilting it. My main use for this would be flat zippered pouches that don’t need to stand up but need something to make them feel soft, and smaller projects can’t handle the thicker Thermolam in the seams.
Pellon Thermolam – This one is the “fleece” that resembles polar fleece in thickness, although it’s not a good idea to substitute polar fleece. Thermolam is good for adding softness or puffiness to a project, but it is quite floppy so if you want your bag to stand up you need to pair it with something else and possibly quilt it. This is good for any project that needs batting (cotton or otherwise). I’m sure there are arguments out there for using poly vs. cotton. I experiment and use whatever I have on hand. I used Thermolam in the laptop sleeve that I just made, along with SF-101 and Pellon 40.
Cotton Batting – Buy a huge package of this when it’s on sale at the Big Box Craft Store and don’t be afraid to cut into it. Use it for pot holders, purses, wallets and more. It can be quilted up to like 10″ apart, so even adding a pocket to a large tote bag is going to count as “quilting.” Use it in straps for softness too! For straps where you fold in fourths, cut a skinny piece to tuck under one of the sides before top-stitching. I pre-wash my cotton batting. If you have a front loader, just put it on the gentlest cycle and dry on delicate as well. Most people don’t do this. I know I’m weird, I’m just sharing what I do!
Canvas – White canvas or duck cloth can be used in place of the papery non-wovens. It definitely adds weight, as in heaviness, to your project so make sure you really want to add it. I like using canvas for wallets and pouches that need substance but not puffiness or super-stiffness. This one is a pre-wash MUST, and it will wrinkle a lot so take it out of the dryer while damp and press it flat. If you get a ton of wrinkles, don’t worry, they won’t show through on the final project.
HTC Form Flex – Midweight woven. If you can find this, buy some! HTC Form Flex is amazing. I think it also comes in fusible but I’ve never seen it in person. I found this at one of the Local Quilt Shops and bought the whole rest of the bolt for fear of never finding it again. I use this rather than Pellon 50 in my full sized bags. The woven just moves right and holds curves and shapes very nicely. This is what I used when I made Keyka Lou’s (pattern here) Bucket Bag and my Sammy Bag.
Did I miss anything? Any questions? The thing is, you will probably spend as much time cutting, fusing and pressing as you will spend sewing any project. But choosing the right interfacing, taking the time to fuse it correctly along with measuring and cutting accurately and topstitching are all going to make your project look that much better!