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How to Make a Bowl from Recycled Plastic (HDPE)

Written by PJ
12/07/2022 13:36:08
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Working with recycled plastic is a cost-effective, straightforward, and environmentally friendly way to create some great DIY crafts and projects this summer.

With a small collection of HDPE plastic and a little technical know-how, you can design and make almost anything from a custom set of pens to garden ornaments, and even kitchen utensils.  

In our three-part series on recycled plastic, we have already looked at the everyday home items that are made from HDPE and you can collect and reuse.

We have also guided you through the easy process of melting down milk bottle tops using either a conventional oven or sandwich press. For this final installation, we’ve put together an in-depth guide on how you can create a bowl from recycled HDPE. 
What’s so great about HDPE in particular is that it can be melted down and reformed again and again. If you make any mistakes when creating your recycled plastic bowl or simply want to start from scratch with a new mix of colours, then it’s easier to reuse your existing materials!

Making an HDPE Bowl

HDPE is a safe material that you can work with at home. When molten, HDPE plastic does not give off any toxic fumes and so is a perfectly harmless material for young children to work with! Make sure to always supervise kids when working with hot plastics and use the correct safety equipment, including heatproof gloves.
Materials and Tools
To make a bowl from recycled plastic you will need:
  • HDPE plastic (ie. Milk bottle tops, food storage containers, or reusable plastic water bottles)
  • Oven/sandwich press
  • Greaseproof paper
  • Cooking spray/oil
  • Heatproof gloves
  • Mould/former (ie. Two bowls to press the molten plastic between)
  • Clamps/weights

Melting HDPE

For a small bowl, such as a pet food bowl, you will somewhere between 100 and 150 grams of HDPE. For larger pieces of crockery, like a mixing bowl, you may need as much as 400 or 500 grams of plastic.
We have already put together an extensive guide on how to melt milk bottle tops and other types of HDPE plastic that you can read here, but here’s a brief overview in case you need reminding:
  • You should shred any HDPE plastic into 1cm pieces before melting (milk bottle tops are already small enough).
  • Preheat the oven to 170 degrees Celsius (350 degrees Fahrenheit) and line a baking tray, or both sides of your panini press, with greaseproof paper.
  • Melt the plastic in batches, layering your shredded pieces on top of the molten HDPE.
  • To mix different colours of HDPE and create a marbled effect, you can either melt different types of plastic on top of each other or twist separate sheets of molten HDPE together.
  • Note: Your HDPE should not be bubbling when melting. You are looking for the plastic to become soft and pliable.
After you have a melted mass of HDPE, you need to form it into a block and remove any air bubbles. Here’s how to do that:
  • Transfer the melted HDPE to a square tin or wooden mould/former, which has been lined with more greaseproof paper (this can be made easily by screwing four scrap pieces of wood together).
  • Compress the HDPE into the mould using a weight. You can attach clamps or place the mould into a vice for the best results.
  • Depending on the size of your plastic sheet, it can take anywhere from 10 minutes to over an hour for the HDPE to cool.
  • You can also fold the plastic up and press it together to remove the air bubbles, like we have done here

Once you have eliminated the potential of air bubbles, you are ready to create your bowl! Place your block of HDPE back into the oven/panini press to melt down again.

Forming your Bowl

To form your bowl:
  • Begin by greasing the insides of your moulds using cooking spray or a small amount of oil.
  • Take your melted layer of HDPE plastic and drape it over the top of an inverted bowl or inside your mould. Placing the plastic across the top of an upside-down bowl helps you ensure that the HDPE is covering the whole surface.
  • Place your secondary bowl on top of the first or press your weight into the mould/former.
  • Once the plastic is inside your mould, you need to clamp it shut or place it in a vice. Continually tighten the vice/clamps every few minutes as the plastic will shrink while it cools.
  • If you do not have any clamps, you can place heavy items or weights on top of your bowls/moulds to keep them together and force the molten HDPE into place.
  • While the plastic is still hot, you can try to remove any excess HDPE from the edges of the mould using a knife.
  • A small plastic bowl may only take 20-30 minutes to cool, while a larger piece could take over an hour.

Finishing your Bowl

To finish your recycled plastic bowl:
  • Remove it from the mould and trim any excess plastic from the lip of the bowl using either a bandsaw or handsaw.
  • You can sand down the rough edges of the bowl using a range of sandpaper of different grit sizes, beginning with a lower rating (ie.120), and increasing the grit size as the bowl’s edges and sides become smoother.
  • A range of plastic polishes are available to help give your HDPE recycled bowl a shine. Buff the bowl using polish and a microfibre cloth.
Now your HDPE bowl is complete! If you are not happy with the finished project or if it has any noticeable imperfections/air bubbles, melt the plastic, and begin again. As HDPE plastic is food safe, these creations can be used around the home for a variety of different purposes. Just make sure to clean the plastic with warm, soapy water before using it.
If you want to start making some DIY projects at home, but do not have a large collection of HDPE plastic to hand, you can order bespoke sheets from our website.

We cut HDPE and other recycled plastics to any size and shape! Get an instant quote today on our website.
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