Waste Plastic vs New Chair

/ By Marta

It’s amazing what SOME can create with what OTHERS throw into the sea. Studio Swine shares with everyone a manual so others can build the chairs too.

I’ll try for sure, any volunteers?

Here is the “Recipe“.

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1 camping stove
1 Food tin
1 Steel kitchen pan with lid
1 Cooking thermometer
Thick tin foil
Glass fibre roofing insulation
Crushed Charcoal (for best results use perforated charcoal from an old water filter)

1 Scrap aluminium L section (6cm x 6cm x 40cm approx.)
2 Steel sheets (for best results polished stone off cuts from kitchen worktops, sink cut-outs or leftover floor tiles)
Wax for mould release (beeswax or car polish)

1 metal scraper
Drill + metal bits
Screw driver
3 long screws
1 or 2 small bolts & nuts

For Collecting:
2 buckets
kitchen or fine garden sieve
dustpan and brush
big bag
rubber gloves



1. Collecting
Collecting plastic on the beach is the easiest way to get sea plastic; it prevents the washed up plastic returning to the sea to harm marine life.
Look at beaches during low tides where materials have been deposited, these are generally sandy beaches with debris along the strand line.
A dustpan and brush is effective for collecting small plastic pellets known as nurdles. These are often found deposited in lines below the main strand line of heavier materials such as seaweed. If the sand is flat and damp, then they can be swept off the surface without collecting the sand. Where sand is collected, they can easily be separated by sinking in a bucket of water and scooping out the floating plastic with a sieve.
Try to sort the plastic at this stage using the plastic chart, separate PET from LDPE, HDPE & PP which share similar melting points. Dispose of any PVC or Polystyrene collected. Small plastic pieces and nurdles are not possible to identify easily but if your averages are correct with the large items, the mix will work.
The plastic should all be broken up into pieces around 1cm x 1cm, this can be done by hand or a kitchen food processor. Add some water to the mix when using the processor to avoid the plastic from melting around the blades.
Remember: Dry the plastic before melting.

2. Melting
Some essential precautions should be taken when melting plastic. Some plastics emit toxic fumes when melted. The lid and filter will help minimalise exposure to these, but also do any melting in a very well ventilated place away from others, outside if possible. Use a good mask and goggles to protect your eyes from smoke. Hot plastic will stick to the skin, so always wear thick gloves and long sleeves, leather gardening gloves are fine.
In the manual, there is a chart to identify plastics. However, chances are you won’t be able to easily identify a lot of the plastics you’ve collected. The key is to collect a sizeable amount of plastics of the same type so that they will mix well together when melted. It’s common to find large amounts of the same type of nurdles on a particular beach near where a spill once occurred, after you’ve indentified the melting point they can form the majority of the mix that glues the rest together. Other beaches may contain mostly PET due to large amounts of discarded drinks bottles whilst some beaches contain a mix.
The majority of plastic waste is made of type1, 2, and 4 plastics. Wherever possible, avoid polystyrene and PVC, as they emit toxic fumes. The plastic pellets, or “nurdles”, are all thermoplastics, which means they can me re-melted. Small plastic fragments found in the top layer of the ocean are most often HDPE, LDPE, and PP, as they are less dense than sea water and float, but, even if the plastic you find are thermosetting (which do not melt) they will still form an aggregate within the melted mass.
Once you have sorted your plastic and prepared it for use you can add them to the furnace.
Check the pan when the temperature reaches around 180ºC. If the mix is still hard, turn the heat up to 250ºC, checking at intervals to see when the mix is molten. As soon as the mix is molten enough to form a doughy ball in the pan when stirred, it is ready to use. Don’t worry if some of the plastic pieces aren’t fully melted, as long as the majority are, they will form a colourful aggregate within the material. Be careful not to leave the mixture too long, or the plastic will begin to burn and create more toxic smoke.
You need to decide whether your plastic mix is mostly Type 2, 4 & 5 or Type 1. In most cases it’s best to make a mix that mostly consists of Type 2, 4 & 5 which melt in the range of 110 – 170°C and use the Type 2 (melts at 250°C) as a aggregate.
If melting mainly Type 1 (PET) the plastics with a lower melting temperature can be added when the mix is molten and the stove turned off just before filling the moulds.
To make a stool, it’s recommended you heat around 3 batches of plastic separately, filling the pan each time about 1/3 full. Adding too much in one go will make it difficult to achieve an even temperature through the mix. An improvised windshield may be required for your furnace to reach higher temperatures.

3. Casting
Polish the leg mould with a cloth, and preheat the mould over the gas stove.
Use a metal scraper to scoop the plastic into the leg mould, overfilling them slightly. Press the full leg mould upside down against the flat surface used for seat mould. Press down on the mould until the metal sides are flat against the surface and the excess plastic squeezes out from either end. The excess should be cut off with the metal scraper and added back into the pot to be reused. Submerge the mould in cold water, this speeds up the curing process and makes the plastic contract away from the mould making it easy to remove.
When three legs are complete, a large blob can be melted to form the seat. Polished granite or marble kitchen worktop off cuts are the most effective surface for casting against, a sheet of smooth metal can be used as well, but it should be lubricated with oil or wax to avoid sticking to the plastic. Preheat the surface of the mould so the plastic stays in a molten state for pouring which will result in a smoother finish.

4. Assembling
Mark out an equilateral triangle on the base of the stool where the legs are positioned. Cut each leg at the top & bottom at 11 degrees as illustrated. Drill holes and screw in legs with screws approximately 3 inches long. If required, use some of the leftover melted plastic to weld the legs to the base of the seat to add strength and prevent them twisting.

It is your responsibility to make sure that any project you undertake is safe for yourself and others, and legal for your situation.

Open Source Sea Chair is intended to address the problem of plastic at sea. We are constantly trying to improve the manual, so please get involved and send us any feedback or suggestions to info@studioswine.com


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