I've always enjoyed recycling materials and trying to make new things. I also wanted a pannier bag that doesn't cost a million, or the earth. So I combined these two things to create a convertible recycled pannier bag - it can be worn as a rucksack off the bike or attached to a pannier while riding, meaning no more sweaty back! Once I'd decide what I wanted to make, I needed to work out how.

The basic concept is this:

- As a rucksack, there are two shoulder straps. It has a roll top closure for maximum protection from water, and is fastened by a moulded G-Hook

- To convert to a pannier bag the straps have carabiners on the end which unclip and can be tucked away in a pocket. Moulded hooks are used to attach the bag to the pannier

It turns out that, when you're looking for it, there is a surprising amount of waste plastic out there. The types I used were split into three main categories - HDPE from milk bottles, some sort of PVC kind of material from a banner, and corrugated plastic that I found on the street after an event.

Supplies

HDPE - look for the little number 2 on the bottom (I did also try with LDPE - 4 - and this worked as well, but was a bit softer). I found it most commonly in milk bottles, which were also relatively easy to cut up, but it is also used in shampoo and cosmetics bottles and cleaning products such as bleach bottles. I was informed that the plain white of the milk bottle alone made the hook look like some old chewing gum so I decided to add in some of the green from the bottle lids
Banner - more on how I found this later, but you will need a large section of fairly sturdy material. For my purposes the banner I found was perhaps a bit TOO sturdy, but you live and you learn
Corrugated Plastic - this is for giving the bag a bit of structure (though seeing the point above I'm not entirely convinced this was necessary. I found this on the street from some event signage that had been blown away and stepped on - these signs are currently littering the streets around me, but For Sale signs may be the most common way to find it in other areas
Nuts and Bolts x2 - I did try experimenting with using a recycled material for this component but it was ultimately not sturdy enough and I wanted a bag that didn't fall apart on the first go!
Carabiners x2 - for the straps. You could probably make a recycled substitute for this - perhaps using some more G-Hook style components - but I ultimately wanted it to be very strong so went for some metal ones from my local hardware store
Sewing stuff: machine that doesn't mind some tough material, thread, scissors etc. You could sew it by hand but I decided life was too short.
Melting stuff: panini press, protective gloves, Teflon mats (see the moulding and melting stage for more on this)

Step 1: Collecting Plastic

I spent a LONG time experimenting with the process for melting and making hooks, and this required a lot of plastic. Luckily I have some very lovely friends who saved their milk bottles and other HDPE items from the recycling bin for me - it is surprising how much milk people are able to drink each week! It felt a bit cheeky asking at first but once I'd explained what I planned to do with them they moved from total confusion to just being a bit bemused.

The trouble with milk bottles is they are used to contain milk. And let's just say I've learned through this project that old milk does not smell like roses - I had to give them all a good rinse, being careful about using soap because you don't want residue on the plastic when you melt it. I also had to take off any plastic that was not HDPE - labels mainly - and sadly throw it away (one day I'll work out something to do with them all!).

After that I cut it all up - this took a while. I definitely found it easier to cut them up as I went along rather than save them all to do in one go - this would lead to very sore hands. I used a swiss army knife to chop them in half and then used scissors to make smaller pieces. You don't have to cut them into tiny chunks but I did end up doing them fairly small as it seemed to help it melt more quickly.

Step 2: Melting and Moulding

Buckle up! This was by far the most time consuming step - it was very easy to mess up on this. I spent a while experimenting with how to make the hooks before I found a way that worked for me. Being honest, the initial ones I made were not works of beauty but at least they worked. You just push them onto the bike rack and they stay on - there should be a bit of resistance which means that once they're on they're on.

I used a panini press with some teflon sheets sandwiched between the plates so that the plastic didn't stick. Melting was surprisingly easy, I just turned it on, put some plastic in there (about a handful) and closed the plates and waited for it to melt. Every now and then I'd take it out to combine the pieces and get it to melt together. When it came to moulding it into the hooks I tried to stretch it into vaguely rectangular pieces - when it is this hot you can actually cut it with scissors if you're fast. I'm still not totally happy with this process - it ended up with a lot of strange looking pieces.

When I thought it was melted enough (and after adding any other colours), I took it out, stretched it slightly and formed it around a piece of MDF that was the right thickness for what I needed. MDF is probably the worst material to use for this because it is rubbish if it gets wet and sometimes bits of it would flake off into the plastic, but it was what I had lying around.

I then ran it under cold water to harden and set it - I had to be careful because it contracts quite a lot if you're careful. I imagine this is not an especially scientifically good thing to do but I wanted it cool quickly because I am impatient and wanted to test it out! I also drilled a hole in the bottom of each one for the bolt to go through - I experimented with recycled ways to do this but they were all too weak. Initially I drilled the holes too high - you need some clearance below the front of the hook to actually get it on to the rack.

Step 3: G-Hooks

This was just something I was trying out, but on the finished bag it was actually one of the parts that worked the best. It meant that instead of using a plastic buckle I could use something that was not only made of recycled materials but also a more efficient and lightweight component.

I tried two different methods for making a G-Hook. The first was using a drinks can to create a sort of cookie cutter style thing and using it to 'cut' the plastic while it was still hot. This worked OK but wasn't sharp enough and the shape that I managed to get wasn't precise enough.

The second and more successful way that I tried was drawing the shape I wanted on some thin cardboard, pushing it into the plastic and using a knife to cut around it while it was still hot. This was more fiddly but ultimately ended up with a better finished product. (after this I lost the swiss army knife and I'm still looking for it! This is my reason for why the bottom of the hook looks so wobbly, I didn't have anything to cut it straight with.)

Step 4: The Fabric

The fabric for the bag was probably the most difficult bit to source the material for. Every time I went for a walk I would see loads of banners up, some for quite specific events that had already ended and therefore the banner would no longer be needed. However I obviously wasn't going to steal one off someone's fence! One day on a walk I spotted something lying on the floor of a car park and lo and behold it was a banner. But when I emailed the owners of the car park to ask if I could have it, they said it was still needed. I resigned myself to the fact that I was never going to find one.

But a week later they emailed again to say they had decided they no longer needed it and did I still want it? Of course I replied yes! And a day later it was in my possession. Being honest, it initially didn't seem like the greatest material once I got it home. It was very dirty and when I first tried sewing on some pieces I found from the edges they ripped. It was made of a material that was almost paper-like in places. However once I started to cut it up I realised that although the edges were hardened, the rest of the banner was fine and I didn't have any trouble sewing it. Moral of the story is I got very lucky indeed! (combined with keeping my eyes peeled at all times for suitable materials)

Step 5: Tracing and Cutting

I cut out the pieces first so that they were slightly smaller before giving them a good scrub in the sink. This was also a good way to check that they were waterproof (or at the very least water resistant).

The bag was originally going to be made of a combined front and side piece, a back piece and a bottom piece. However when I went to cut it turned out the banner was not the right dimensions for this to work so it was back to the drawing board. I settled on one long piece for the back, front and sides, and then two side panels. I think this way works well if you have a long piece of fabric and it wasn't as fiddly as I thought it would be to sew.

I wanted to preserve some of the pattern of the bag so I made sure to have words or symbols that I liked in strategic places - for example the letter W was used for the water bottle pocket.

I would say this wasn't an exact science, I just sort of went with the flow. It is essentially a box with added bits on, if you didn't want it to convert into a rucksack or have any pockets or handles it would be even easier.

In all I would say I cut

1X front/back/base piece
2X side pieces
2X side pockets
2X straps
2X small pieces for loops to hook the carabiner on to
1X external pocket (to tuck straps into)
1X internal pocket (to hold the corrugated plastic in place)
1X handle piece
1X long strip to cover up the mess at the back and hold the straps in place
2X small strips to attach to the ends of the G-Hook

Step 6: Sewing Part 1 - the Straps

I'll give a brief overview of what I did because the basic process is 'sew a big cuboid with some bits on it'.

measured the back piece to ensure things were attached symmetrically and checked there would be enough room for the hooks
folded each strap piece in half across the long end and topstitched (I used red thread because I thought it looked cool against the black, but if I had any orange I would have preferred to use that to match the banner
fold handle piece in half and topstitch. Also attach a small long strip in the centre - for the G-Hook
tape the straps and handle underneath a long strip and sew all the way along the top and bottom
sew down the back pocket piece along the bottom and topstitch to the bag, adding a small loop of elastic which will be used to hold the bag to the pannier rack
hem the top of the pocket, attach velcro to the inside of the pocket and the corresponding point on the bag

Step 7: Sewing Part 2 - the Pockets

I didn't have any pockets on the original plan because of the way the bag was sewn, but I decided they would be useful and I was able to do them when I sewed the side pieces separately. I folded the material at the bottom and stitched it down to hold it into place. This pleat meant it could hold a fair volume. I considered making a rounded bottom but I decided this way was the most efficient use of materials.

Step 8: Sewing Part 3 - Other Bits

I sewed a large pocket to the inside of the bag right up to the point of the strap attachment on the back. This is to hold the backing that keeps the bag in shape.

I also sewed a small loop on the front for the G-Hook to hook on to.

I made two small strips of topstitched and folded material to be used as loops to attach for the carabiners to hook on to.

Step 9: Sewing Part 4 - Putting It All Together

When putting it all together I first sewed the sides to the back, making sure to slide in the loops at the bottom so that when turned right side out they would work. After that it was just a case of making sure everything was under the needle and I was sewing in a relatively straight line. The more I sewed the more the bag took shape (good) and became more awkward to sew (bad). You really have to fight with the material to get it to do what you want!

It was even more of a fight to turn it right sides out - it felt like fighting a baby octopus. The material was extremely stiff, at one point I stuck my head inside the bag to try and help (don't do this, you just end up with a sore head). Eventually after fighting with it for ages I had an actual bag-looking thing! I then topstitched around the top of the bag and it looked close to being done!

After working out how big the roll top would be, I stitched down the G-Hook accordingly, making sure it was in tension so it wouldn't come loose.

Step 10: Adding the Hard Backing

I cut a piece of corrugated plastic from my street sign to the same size as the pocket - I cut it almost exactly the same size rather than a bit smaller, so it was nice and snug and didn't wiggle around. This wasn't strictly necessary because the bag ended up being very sturdy by itself but it was still useful to have as something to screw the hooks into.

Step 11: Attaching Hooks

By this stage the end point was in sight! I cut a small hole in the fabric on either side of the straps, and use a screwdriver to widen the hole in both the fabric and the corrugated plastic. It was then a simple matter of screwing on the hooks, tightening them with the screwdriver as necessary.

I also stitched the straps to the carabiners.

Step 12: Does It Work?

The answer is....Yes!

The hooks work well and the bag stayed fixed to the rack for the whole of the test ride. It also works well as a backpack.

One thing I would change is it is a bit too square for my liking, I would make it slightly less wide. My foot did hit it a couple of times while pedalling, although it wasn't a major issue.

Overall I'm really pleased with how it turned out, and will definitely be using it on bike trips in the future.