Monday, January 28, 2013

Make A Bag Chapter 5: Reversibility and Other Magical Traits- A Case Study



Okay..... so, let's talk about reversibility.

(Inhaling).

I feel like I might end up being The Bad Guy in this post. I mean, I'm going to be very pragmatic about reversibility and, in doing so, I fear that its losing its glamor and wonder and amazingness and novelty might make everyone disillusioned about sewing in general. It's like my children thinking that stars are awesome and shiny and sparkly and then I come along and say, "Actually... they're roundish. And they're gas and they're burning and it's all light and heat energy and they're not pointy."

I've shared my thoughts on reversibility in earlier posts like this one and this one so I won't repeat them here. In short, reversibility is a fun side-effect of good tailoring but a lot of it is also hype. And hype is like one of those details in bag design - it's distracting. I used to promote my projects as "Reversible!!!!!" in the past because it sounded very cool. Then I started feeling guilty for essentially misleading you (I'm sooooooooooo sorry!) and stopped. I mean, I didn't want to you to think I was a superior seamstress because I made reversible stuff. Ewwww! So today let's demystify reversibility once and for all and then you can objectively decide if it's something you want your bags to have or not, okay?

(Exhaling).

Let's start with the General Formula for Reversibility. You didn't know there was a formula? Tsk. Well, here it is:

Reversibility =  Layers + Shared ElementsSymmetrical Features

That's the general formula, by the way. By that, I mean that most bags are only double-layered i.e. they have a lining, so they are reversible to only either of both sides. In other words, most reversible bags are two-way bags. If there were a way to make a bag with three or more layers, you'd get a three-way or four-way (or more-way) bag which would still be reversible, in a sense. And yes, I've thought about it. But I then got distracted by life and chores.

So here's the special formula for two-way bags, which are just bags with lining, with which everyone is more familiar anyway:


Reversibility =  Lining + Shared Elements + Symmetrical Features


Let's unpack those three parts of the formula:

A   Lining
We dissected this at length in the last post. A lining is the minimum requirement for reversibility. This is because reversible things need to have two sides that look equally "right-side out". There is an exception: if you use naturally double-sided fabric and have impeccable workmanship and perfect machine tension. So, unless your bag is made of, say, double-sided neoprene and you have an industrial machine that can perform the perfect coverlock stitch through rubber, your reversible-wannabe project will need to have a lining.

B   Shared Elements
These are the shared parts of a two-sided bag - the single (not double) things that are in use when either side of the bag is facing out. These are usually connected to the parts of the bag where both layers meet e.g. the strap, the top zipper, the flap, tie, corded loop for button, snap hook, etc.

For a bag to be truly reversible, these elements must be equally shared by both surfaces of the bag. They cannot have a discernible "right/front side" and "wrong/back side." They also cannot 'belong' more to one surface than the other.


Not Reversible                       Reversible



Not Reversible                       Reversible


Not Reversible                       Reversible

 Not Reversible                       Reversible


C   Symmetrical Features
These are other details that, when present on one surface of the bag, must be mirrored on the other. Therefore, unlike Shared Elements, these are often present as doubles. Buttons, magnetic snaps, hook-and-loop tape, even those dangly straps with a swivel hook to hold your keys should be featured on both sides of a reversible bag. Piping, if present in the seams of one surface, should also be present in the seams of the other, failing which the latter surface will look like merely "the lining" instead of a second side. Then there are pockets. Sometimes we make bags with deliberately different outer and inner pockets e.g. flapped-and-buckled cargo pockets for the outside, zippered welt pockets for the inside. When this bag is turned inside out to feature its other surface, will that "inside" zippered welt pocket look odd staring out at the world while the buckled cargo pockets nest within? Here's another example: heavier duckcloth with faced and piped side pockets and reverse applique on one face, and much lighter quilting cotton and a zippered welt pocket on the other - is this a truly reversible bag? While it could be (because it's lined and has shared, reversible straps), it was actually never designed as one.

This next bag, however, was. It has simple patch pockets on both surfaces - not quite as edgy as the earlier bag, but more symmetrical, and thus more truly reversible.


Obviously, reversibility is not limited to tote bags. Once you understand that, you will free yourself to applying the formula to anything you sew. Observe:

Bibs: lined + shared velcro = reversible.

Pouch: lined+ shared reversible strap = reversible

Superhero cape: lined + shared velcro fastener+ emblems on both sides = reversible.


Winter hat: lined+ shared ear flap braid = reversible.

Winter hat: lined+ shared cuff = reversible (if you don't mind the pompom smashing into your skull).

Summer hat: lined + shared brim = reversible.

Mittens: lined+ shared elastic channel = reversible.

Dress/blouse: lined + shared button/velcro placket = reversible.

Vest: lined + embellishments on both sides (construction worker and sherrif) = reversible.

Faced pinafore: Lined (if you extend the facing all the way to the hem)+ shared buttonhole +buttons on both sides (if desired) = reversible.

Trousers: lined + shared waistband = reversible.

Hoodie: lined+(if present) shared reversible zipper = reversible.

See? I don't think I need to go on.

Now that we've introduced the theory of reversibility, let's dive into some application. We're going to make three bags today. They are exactly the same bag but in increasing degrees of reversibility.


Case Study A: The Unreversible Bag

This is one of those ubiquitous reusable shopping bags that grace the checkout displays of supermarkets:

They're the ones that fold 


up

and snap shut.

This bag is made of Polypropylene (PP) Spun-Bonded Non-Woven Fabric aka shopping bag fabric. Read more about it here. I picked this fabric not only because it's exactly what all commercial shopping bags are made of, but because it doesn't fray. It is single-layered except for its base, which is lined to allow for rigid base inserts. There is no interfacing because it is unlined.


Being unlined, the seams of this bag will need to be finished. We could panic over this or we could use it to our advantage: make externally bound seams that will provide an angular frame for the bag. So let's choose to construct it as a Block Tote (see this post for schematic diagram). 

Reason: since all its pieces are separate, the Block Tote structure has the most seams (and no folds in the fabric), which in turn provides the fullest reinforced frame. 

First, hem the top edge of the bag to the WS. Then make (reversible) two-sided straps and attach them to the bag. 

Sewn onto just the outside(RS) of the bag, the strap belongs only to this outer surface of the bag. So while the strap itself is reversible, the bag+strap combination isn't.

Next, sew both base layers together, RS out, with stitching lines (yellow) to divide them into two chambers for the base inserts. Two lines (rather than one) are used to allow the base to fold along a broad spine to accommodate the bulk of the collasped bag. Attach the base at three sides to the body pieces, leaving one side open to slide the inserts in.

Sew up the remaining seams of the bag. These are external seams, which will be bound later.

Make double-layered flaps for snaps.

Baste them to the outer base.

Bind that edge, fold the flap back and topstitch it down.


Then bind the remaining external seams,

folding the top edge of the binding into itself.

Finished - outside

and inside.

Verdict: Single layer+ straps sewn only on the outside (RS) of bag + snap flap sewn only on the outside (RS) = Not Reversible


Case Study B: The Almost-Reversible Bag

Same bag but now lined, and in a cloth fabric.

Since it is lined, we do not need to finish the seams of this bag. So we're opting for the Bucket Tote structure (see this post for schematic diagram) - it has the fewest seams and the smoothest finish. Fewest seams = least bulk when sewing layers together.


Start by making reversible two-fabric double-layered straps, just as before.


This is a Bucket Tote, but with a rectangular base. So divide the body of the bag into the four sections that will attach to the four sides of the base. Center the straps within the front and back sections and baste them on.

Fold the body with its WS out and sew the single seam to turn it into a tube.

Make flaps for snaps as before. We used interfacing this time, since we are using actual fabric.

We also used magnetic snaps instead of regular snaps, just for fun.

As in the previous bag (Case Study A), the flaps were basted in place on the outer base.

In the previous bag, only the base was lined. In this bag, both the base and body of the bag are lined, so the construction process from this point on will be quite different. First, place the two base layers with the WS together. Sew two lines of stitching to separate the chambers for the base inserts as before. However, do not sew to the edge of the fabric; stop at the SA of the base. This is to keep the two layers separate at their SA so they can be individually attached to their respective body layers.

Attach the outer body to the outer base, peeling the lining base back and out of the way. The pink arrows indicate where we'd stopped our earlier stitching lines to enable the outer bag layer to be assembled independent of the lining layer.

Repeat this process to attach the lining body to the lining base. You will now have two bags attached only along those two parallel lines that separate the insert chambers.

Introduce the base inserts into their chambers,

line up the edges of the two base layers

and sew the two base layers to each other, stitching (see black stitching lines) only within their SA so the stitches don't show  on the RS of either layer. Leave the corners unsewn if you wish - they are tricky to manipulate and the gaps will not show when the bag is turned RS out anyway.

Turn the bag RS out so that all the raw SA are enclosed within the layers. You can, if you wish, edgestitch the base.

Fold the SA at the top edges of both layers to their WS and topstitch them together.

The bag is complete.

The straps, being sewn into the top seam of the bag, are now shared by both sides equally.

However, the snap flaps are again sewn into the base seam of only the outer (NYC print) fabric layer


with no corresponding flaps on the other surface:


This means the bag can only fold up in one configuration: with the NYC print fabric facing out.



Verdict: Lined + Shared Straps + Snap flap sewn only to the outside of the bag = Only partially reversible.


Case Study C: The Fully Reversible Bag


We made the same bag as in Case Study B - Bucket Tote, lined, with double-sided straps sewn into the top seam.

However, we made two pairs of snap flaps this time, and sewed them into both layers - the NYC print layer and the elephant print layer.

so that the bag can be folded and snapped shut with either fabric side out.

Verdict: Lining+ shared straps+ snap flaps symmetrically added to both surfaces = Fully (and thus truly) reversible.


Voila! Use the formula, friends. And know, therefore, that what you might have thought was magic, actually is Math. 

So now that we agree that reversibility is not a big deal in bag design, let's look at something else that actually is fun: transformability!

It could well be that I am the only person on the planet that thinks this is exciting in bag design, so if this part goes right over your head, please excuse me when I say that morphing bags are great. I'm sure that somewhere, some time, someone has critically analyzed bag transformability, too, and reduced it to a simple formula. If so, I'd love to read their report! However, until then, I'm going to bask naively in my enjoyment of Bag Shape-Shifting. Here are just two examples:


This fruit bag

that spits out its insides to become a flat tote.

And these bucket totes

that fold flat


and zip up

to become coin purses.

And everyone knows those little bags made entirely of a single zipper that zips itself up. Comes in all shapes- flat, pyramidal, etc. Zippers have a magic all on their own, don't they? 

Now, isn't transformability fun? I think so.


We've finally finished deconstructing - shape, straps, layers and closures! And, now, reversibility, too. In the next few chapters we will reconstruct specific bag types. There will be less theory and more application, in much shorter posts, phew. See you then!


7 comments:

  1. Very interesting... I've never thought much about it. Thanks!

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  2. I have to confess I've never found "Reversibility" to be a feature that I wanted, in anything? Except maybe one of my aprons and that is because I choose the side that matches my outfit better.

    Usually though it seems like a waste of effort in most cases, for something that I would in all likelihood never reverse. Or even laziness in not figuring out a better solution for finishing seams or hems (like for example, making play dress reversible so you don't have to figure out how to make a neck facing or hem).

    ... but maybe that is just me?

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  3. I don't know how to sew bags, but your tutorials make me want to make all of them! Thank you so much!

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  4. BRILLIANT post!! Thank you so much for taking the time to write it! :-)

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  5. My kids ADORE the reversibility of their owie doll clothes!

    I really love your bag posts. Have been sharing them, because they are brilliant.

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  6. I had never put much thought into reversibility...until now!! Intriguing! I have also been intrigued by the purse cover concept. If you are familiar with the home party companies www.whatabag.miche.com bag shells and www.thirtyonegifts.com purse skirts, you know what I am talking about. If not, they have a base bag in several sizes and several different types of handles. Rather than buy more bags, you buy the shells or skirts to change to look and function of the bag. I like this idea but, even if I could afford it, I wouldn't want to put that much money into a bag/purse. Brand name status symbols hold no interest for me at all.
    Would this be something you would be interested in posting about? I would like to know how make and attach a functional shell to a basic bag/tote/purse.

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  7. I like the reversible bag at the top best. It can go with lots of outfits. The wearer can switch it up when they want to look different.
    I have always liked pretty bags. In fact, I sometimes make my own. Sometimes what I see around me isn't as colorful as I would like.

    I prefer casual bags because you can usually get more creative with those. When it comes to bags for work, you have to stick to more conservative lines and colors.

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