How to sew a reversible two colour bag!

Have you ever wondered how to design and make a handbag from scratch? Where you can choose the shape, colour, fabrics, number and size of internal pockets, placement of key hooks, length and width of the strap? What about a bag that has sides that are colour reversible, so that it suits more than one outfit?

I rather enjoy sewing - it's a useful hobby I can happily pursue when I'm not feeling quite relaxed or creative enough to paint. I'm especially fascinated by colours and patterns, and choosing pretty fabrics for a project makes me quite happy!

I prefer to design patterns for sewing projects myself, rather than use pre-designed or purchased patterns from magazines or books. That's the real fun of sewing for me - designing my own sewing project (be it a bag, book cover, piece of clothing, patchwork quilt, etc), challenging myself to think through the various steps in the construction process in advance (so I don't end up with the hems showing and the zips facing the wrong way!), then watching the project come to life the way I envisaged.

Some years ago I designed a two-colour bag that had a different fabric pattern on each side - it was essentially reversible (not inside out reversible, but certainly side to side).

Designing and making this bag wasn't particularly difficult, although it was important to consider that the centre strip piece that joins the two sides of the bag (to make it have thickness or width at the base, rather than being a flat pocket), and the over-shoulder strap, would need to be equally representative of both fabrics (which meant slightly more sewing than usual).

That old bag has been slowly disintegrating through wear and tear over the years (I have loved it so!). Cotton fabrics have a tendency to wear more with use than synthetics. So I decided it was time to replace it!

This time, I was going to make a slightly larger bag, so I could fit some of my books in there as well as my purse and keys. First, I chose the fabric colours and materials (I use patchwork quilt patterned cottons because in addition to pretty colours and patterns, they are sturdy fabrics with an even straight weave that doesn't pull in odd ways when sewing around curves).

Fig. 1 shows the fabrics I chose to use for the sides of the bag (already cut out around a paper pattern I drew in the shape of a crescent moon), plus the dark bottle-green lining fabric, as well as suitable zips, bias binding, matched-colour threads, metal bag loops, key hooks and buttons.

Usually when creating a sewing project, it's important to consider carefully the list of steps that you'll undertake in sewing it to assemble the pieces together. In this case, I start with the lining fabrics for the inside of the bag, and attach any internal pockets and other items such as zips and hooks. I used doubled-over bias binding to attach the hooks to the liner. I zigzag all seams to prevent fraying (see Fig. 2).

Attaching the internal pocket zips can be tricky - it's important to prevent seams (and zip ends) from showing, and to align the pockets carefully with the main lining fabric. I'm certainly not an expert in these techniques, but I've developed some tricks that give me the result I'm after. Sewing zips must be done with a special zipper foot that helps you to line up with the bulk of the zip itself, without the presser foot being pushed away (see Fig. 3).

Once I've sorted out all the internal pockets and hooks, I then need to join the outer fabric sides to the liner fabric on the sides - it's crucial to remember to sew with the 'right' sides (or the patterned sides) of the fabric together (so when you turn the seam the other way, the 'right' sides will be the ones you will see on the outside).

I tend to iron all my seams flat and pin them to ensure there's no movement between the top and bottom pieces as I'm sewing. This is especially important around curves, as fabrics can stretch in unexpected ways when sewn on the bias (diagonal) (see Fig. 4).

Once the outers and liners are sewn together at the top, and after a line of zigzag stitching (close in to the seam), I cut little darts (or little nicks in the seam) only through the waste fabric of the seam (being careful not to cut the zigzag line or the straight stitch of the seam) in order to be able to stretch the seam in the other direction.

This is important on curved seams, because otherwise when you turn the seam inside out, the fabric in the seam will be tighter than the remainder of the fabric, preventing it lying flat. I then iron the seam flat, and sew a straight stitch over the seam from the right sides of the fabric, approximately 2-3 mm from the folded edge. This holds the seam together and keeps it sharp (see Fig. 5).

Once the top seam has been completed, it's time to think about the base of the bag and how that will come together. By this stage I've already sewn straight seams down the fabric that will join the two sides and make the width or thickness of the bag. I've joined the two outer fabrics together and flattened the seam, and then I've tacked the liner fabric to the outer fabrics.

Next I place a row of pins around the base of the sides of the bag to line up the outer and liner fabrics (see Fig. 6). This line of pins will be followed by a tacking stitch (which could be done by hand, but I'm just as happy these days doing it with the longest stitch length available on my sewing machine (6.5 mm)). This long stitch length is essential because the tacking stitch is simply intended to hold the sides together temporarily - I want to be able to remove it easily in case it shows from the outside in the final bag.

With the tacking stitch in place, I can remove the pins from the sides of the bag, and instead, I will be able to use a row of pins to attach the sides of the bag to the 'width' piece. Firstly I mark the symmetrical centre of each side (ie, of the crescent shape), as well as the half-way point of the 'width' piece, and I baste these all together.

Then I add pins to join the sides to the 'width' piece, and proceed to sew them together (Fig. 7).

This is undoubtedly the most difficult part of sewing the entire bag. Since the bag is curved, I'm having to fit a three-dimensional shape of fabric in and around my sewing machine arm, turning it in the direction that provides the best visibility and flattest working surface just about every few stitches (and don't forget that here I'm also sewing a curve, so I need to be careful to keep the seam as flat as possible and well lined up as I go).

I make sure that the 'width' piece narrows towards the points of the crescent, which is where the bag loops will go for the straps to be attached to - here the 'width' piece needs to be approximately equal to the width of the metal loop. After the seams are done, I cover them with a

The bag is almost finished by this stage - just the main zip and the strap attachments to go. The main zip is a bit tricky. I've measured it carefully so it will exactly fit in the curve of the crescent at a measured distance from the top edge. This means I need to keep this exact distance for both sides of the zip. I measure this carefully, and pin it exactly.

If you've sewn big zips before (and these were jacket zips, for ease of opening), then you'll know that the zipper head is so big you need to move it aside to prevent it pushing your zipper presser foot away as you sew past it. Furthermore, as you finish sewing one size of the zipper, you're left with a challenge to sew the other side while keeping the seam on the inside of the bag... so you have to open the zipper right up, and sew from inside the bag (see Figs. 8 and 9).

Once the main zipper is on, then I just have to attach the straps. I use the remainder of the 'width' piece of the bag at either side (the points of the crescent shape), to enclose the metal bag loops (see Fig. 10), and fold it over to prevent unsightly seams.

The bag loops carry the entire weight of the bag, so the join here must be very sturdy - I create a box-barn shape with my stitch lines and sew over this folded section many times (see Fig. 11).

Finally, I add the strap (two-colour, to match the different coloured sides of the bag), and I fold the strap and attach buttons in order to make the length adjustable (see Fig. 12).