Welcome back to the Make A Bag series! So far, we've covered basic structural bag shapes and some typical straps. We mentioned that straps, being an integral part of bag design, affect what the bag pattern will look like when it is drafted. Once you've decided on the design of your bag (size, shape, straps, etc.), you'll need to decide on its layers - how many? What kind? How thick? The layers of a bag will determine how you actually sew the pieces together. Today, we'll be dissecting and analyzing bag layers, broaching bag closures and suggesting some approaches for finishing a bag in the presence or absence of certain layers, particularly the lining. There will be many disparate ideas to cover, so expect it to feel a little "all over the place"!
LAYERS
These are some typical layers of a bag, not all of which are always present:
Outer layer
Stabilizer (interfacing)
Inserts
Lining
Let's break them down individually.
1 Outer Layer
This is the main bag, the part that people actually see. In an unlined bag, this is the entire bag. Now, in garment sewing, the garment is often left unlined, especially if it is a casual garment or one in which thermal insulation is not important. In use (i.e. being worn), only the outside of a garment is visible; nobody needs to see its underside. So it is common for garment seams to be serged and left exposed . Bags, however, subject their inner surfaces to scrutiny every time the bag is opened to access its contents. A lined bag provides a very neat and finished view of these inner surfaces. An unlined bag doesn't - it has seam allowances and bottom-stitching, for instance. We can't do much about the bottom-stitching but we are obliged to finish those exposed seam allowances, both for strength (fraying edges are weak edges) and aesthetic appeal. Some ways to finish the seam allowances on the WS of an unlined bag are
Ignore them completely - possible for fabrics that don't fray, like felt, fleece, nylon, leather, vinyl.
Pink, serge or zig-zag them. If you're making a tote with your kid, serged edges are perfect. And there are many occasions when, to save time, I've mass-produced light carrying pouches with serged seam allowances. However, if we're making a bag that is intended to bear substantial weight or that we're planning to sell for more than, say, the cost of a Happy Meal, maybe the bar needs to be set a little higher. See next few points -
French seams or fell seams. I will use this method whenever I can. Sometimes I even use these externally on lined bags, for texture. You get to see this later in this post. These aren't suitable for all fabrics, though -some really thick fabrics (like packcloth) don't allow this.
Bind the SA with tape (twill tape is common) or bias tape, or just random strips of fabric. Sometimes, this is even used in lined bags in which the outer bag and the lining are sewed together as a single layer, leaving exposed SA on the inside of the bag. This seems to be the method of choice in commercial bags e.g. backpacks and others with zippered openings. See picture below:
2 Stabilizers
Also known in some circles as interfacing. Stabilizers are so called because they um.. stabilize the fabric i.e they make fabric stiffer, stronger or less likely to rip, shear or stretch in any particular direction. Many materials can be used as stabilizers; some are commercially-prepared stabilizers, while others are just other fabrics found in your stash that have a more suitable weight than the one you are trying to stabilize.
Here are some materials I've used as stabilizers in my bags:
Some notes:
Nylon packcloth is just lovely. It comes in many weights. Some are even coated impervious on one side, making it a naturally waterproof sew-in stabilizer.
Those crib mattress protectors are my best-kept stabilizing secret. They are the best ever stabilizers for fabric backpacks - just the right puffiness, thickness and stiffness and with a middle waterproof layer, besides.
I use canvas/twill as a sew-in stabilizer. It's soft in a way that commercial stabilizers are not, while still lending a nice weight to the fabric it stabilizes. Sometimes I use it as a non-batting (i.e. non-puffy) alternative for quilting, like in this bag.
Commercial interfacing - here's what they might look like on bolts:
These are the two kinds I use a lot-
heavy weight sew in stabilizer, which is slightly puffy and which is sewn to the SA on the WS of the fabric pieces. It's lighter than canvas.
craft-fuse, which is fusible (i.e. iron-on) interfacing that is craft-weight. Craft-weight= stiff. Not for garments, unless it's a robot suit. I know that lots of people hate craft fuse. I hate it, too, and for the same reasons: it wrinkles, it's crumply, it feels unnatural etc. However, I also love it because it makes gloriously stiff straps. I will share two tips for preventing wrinkling with this heavy fusible stuff:
Only use it with fabrics that are heavier than it e.g. duckcloth, canvas, some homedecs. Never use it on regular cotton, satin, flannel, gingham, etc. If you're needing something as heavy as craft fuse to stiffen something as floppy as quilting cotton, you're clearly using the wrong weight fabric for your project. Go shopping for something heavier. All that said, I do that, too - love a designer print in quilting cotton weight and try to stiffen it to death. It's hard to fight a good print. See next point.
If you insist on sewing with a lightweight fabric and need it stiff, you can still use craft fuse (or any heavy fusible interfacing). Just don't fuse it to that lightweight fabric. Cut another piece of heavy material (e.g. some canvas, batting or even sew-in interfacing) and iron the craft-fuse to that. Then sew that composite layer to the WS of your lovely lightweight fabric. That way you get all the stiffness you want but without the wrinkling.
3 Inserts
are additional materials that I include for special functions. Some of these are:
Heat-insulation and deflection inserts (Therma-flec, Insul-bright) etc.
Waterproof inserts
Base inserts - for making rigid bases of bags without having to resort to cardboard. You all know I love cardboard, but it doesn't survive washing. I've used template plastic (very light and flexible), plastic canvas (medium flexibility) and flexible cutting boards (much heavier).
4 Lining
Forgive me for climbing onto my soapbox now but I really like lining my bags. It isn't just for aesthetics. Remember that once you introduce interfacing or inserts, they are visible from the inside of a bag, so you will need to conceal them under a lining or else flash them to the world each time you reach in for your wallet or breath mints. The same goes for anything - like the pouch of a welt pocket, for instance - that visibly protrudes from the back of the outer layer into the bag cavity. Let me share some other advantages of lining a bag:
robustness and structure
reversibility
aesthetics
concealing the backside of stitches
adding pockets
possibility of interfacing
possibility of base inserts
installation of hardware
possibility of waterproof inserts
possibility of heat-resisting inserts
natural casings and channels between layers, for drawstrings etc.
Of course, there are instances when I will choose to leave a bag unlined. Most common are:
I'm mass-producing them for a party and I don't want to take the time to cut double of everything.
The fabric is already very heavy and the bag is relatively featureless, so that it neither requires interfacing nor the concealment of innards of pockets, for example.
I was already planning to finish the seams externally (e.g. bound or french seams) for some aesthetic value.
FINISHING A BAG
The presence of absence of a lining greatly affects how the bag pieces are assembled and how the bag is finished.
Without a lining, you'd have to finish the seam allowances. See Section 1 (Outer Layer) above for some ways to do this. And while we're on the topic of finishing SAs, let's discuss french seams:
They're quite popular on bags because they reinforce and emphasize the edges of the bag and square out its overall shape.
This is a fold-up shopping bag I made. See the blue arrows indicating those side seams that emphasize the angularity of the bag.
These are actually bound seams. Externally bound by a strip of the same fabric, to be precise.
Bound seams -internal and external - are not limited to unlined bags. You can also do them in lined bags - just sew the lining and outer fabric together as a single layer and then bind the SA like the bag above. Remember this earlier photo?
But those aren't french seams -they're just bound seams.
Here's a diaper bag I made years ago. Those are the french seams that the blue arrows are pointing at.
I dug this bag out of abandonment (it's never been used) to show you how I do french seams in a bag with a lining, when all the fabrics involved are thick and bulky.
See? Self-explanatory. Make the lining smaller than the outer bag. Or, more specifically, make the lining have regular flat seams and let the outer bag have extra allowance that ends up being pinched like a pleat to make that french seam.
The process of building up a bag from its individual pieces continues until only one, final seam remains. This is often, but not always, the seam at the top/opening of the bag. There are two common ways to finish this last part of a bag:
Turn the whole bag RS out through a hole in the lining (TTWBRSOTAHITL)
Topstitch the rims of the bag and its lining together.
I wanted to show you those external french seam pictures in support of my next statement: I don't do the TTWBRSOTAHITL deal if I can help it. It's like the Whole-Bag equivalent of the Slow Death by Chopstick thing (see this post for explanation) that I don't do with straps. If you aren't familiar with TTWBRSOTAHITL, it's that method that involves a bag and its lining being sewn together at their rims, inside out, to make that top seam. Then everything is turned RS out through a hole in the lining and maybe that top seam is additionally topstitched on the RS. And maybe (if the sewist is not lazy) that hole in the lining is hand-stitched closed, or else it's just machine-run-over. Quite a few bags have been made that way on sewing blogs. It is not an unorthodox method, by the way. However, if you use thick fabrics, interfacing and/or inserts, TTWBRSOTAHITL just isn't practical. Interfacing crumples, canvas gets stuck and frays, plus you spend an inordinate amount of time ironing and re-ironing the bag each time you pull it through the hole in the seam. It can be quite the nightmare. Plus - and I'm finally getting to the point - you can't fully do raised seam finishes like that external french seam in the picture above.
My first choice method for finishing lined bags is topstitching their openings together. In the picture below, the outer bag (green fabric) and lining (white fabric) are individually complete and ready to be sewn together at their rims. The SA of their rims are folded to their WS, the rims pinned (or hand-held) together
and topstitched (or edge-stitched). Here is the lining side of the bag
and here is the outside of the bag.
While the topstitching method is my first choice, there are times when I will choose TTWBRSOTAHITL over the topstitching method to finish a bag, for example:
When there's piping involved at that opening seam.
When that opening seam is curved.
We will be seeing both situations in later chapters.
CLOSURES
To round up bag design, we must look at the closures of bags. Some bags don't have a closure- they are just left open at their tops. Those aside, there is no limit to the ways you can close a bag (and these are just a few):
Ties;
Elastic;
Drawstring;
Purse frame that squeezes;
or twists;
Looped straps;
Zippers;
Buckles, snap hooks and other hardware;
Flap,
which may be full
or partial
and which may or may not have a device for fastening it shut. Here are some common ones:
So: shape, straps, layers, closures, finishing - basic elements for consideration when designing a bag. We're ready to start reconstructing the different kinds of bags now but before that, we'll be spending a little time on reversibility. I was going to include it in this post because of its relationship with layers but I think it deserves its own chapter where I can analyze it to death. That's coming up next!