Carving Material From Plastic Waste

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I've noticed a trend on Instructables and YouTube of people making cool objects out of their used milk jugs and other plastic waste, and I've been meaning to try this technique out for some time. Usually, I like to carve animals and masks out of wood, but it's hard to maintain this hobby in my small college apartment. With plastic, I'm hoping I've found a material that is easier to find and work with using the tools I have available at college. With my limited resources and lack of experience working with plastic, this was definitely an effort of trial and error. I hope this Instructable can help anyone trying to get into working with plastic avoid many of the mistakes I'm sure to learn from along the way!

NOTE: Working with plastic poses a number of safety concerns, including potentially toxic fumes and burns from high temperatures. Always use safe practices and do your research on the source of your plastic.

P.S. I'm new to this plastic work, and this is the first Instructable I've written, so if you have any feedback, I'd appreciate it!

Step 1: Acquire Your Plastic

Using the right kind of plastic for this project is the most important first step. We are looking for High-Density Polyethylene (HDPE), a plastic found in milk jugs and other opaque or colored containers. You will be able to identify if something is HDPE by the number 2 in the recycling symbol stamped onto the material. It is important to use only HDPE, because it melts at a reasonably low temperature, releases little to no toxins when melted, and solidifies into a dense, workable material.

For this project, I used 3 half-gallon milk jugs, a gallon ice cream bucket,and a shampoo bottle (a rare piece of recycling from me with my hairless noggin). Being the impatient crafts-person that I am, I drank a lot of milk over 2 weeks to ensure I had enough plastic for the process. As a piece of advice, just wait until you naturally acquire enough plastic rather than forcing yourself to drink milk, or better yet, forage for HDPE around your neighborhood. This is especially relevant if you have a lactose intolerance. Trust me, your gut will thank you.

Step 2: Processing Your Plastic: Snip Snip

Now for the tedious part. Take your handy scissors and start cutting your plastic into little pieces. I made little squares that were about 1 cm by 1 cm. I've seen other people who have used blenders or other creative methods for quickly processing their plastic, but I don't have a blender available to me. Also, I don't think I would want my milkshake machine used for slicing up plastic bottles, but to each their own! You can see the method that worked best for me in the pictures. I would cut slits until they were almost all the way through the plastic and then trim the comb-like chunk into small squares. Some of these semi-processed pieces ended up looking kind of beautiful, like bird's wings (Pictures 2 and 3). These actually helped influence the first carving that I decided to make out of this material. The quart sized mason jar shows how much plastic I got out of the containers I cut up.

NOTE: You probably don't have to cut your plastic as small as I did due to complications that come up in a later step. I would recommend using thin strips or 1 inch by 1 inch chunks. If you do end up using bigger pieces, please let me know how it goes!

Step 3: Melting Attempt 1

I first preheated my oven to 350 degrees Fahrenheit (~180 Celsius). I then lined a small baking dish with parchment paper, being careful not to rip any holes in it, and filled the container to the top with plastic from my mason jar. I put the baking dish in and started to wait.

SAFETY NOTE: Be sure to always use good heat resistant gloves when working with this material and with hot pans. The molten plastic is extremely sticky, so if you get it on your skin, it's going to burn for a long while!

I wanted to make sure the plastic was good and melted before I tried to condense it, so I waited 15-20 minutes. After this time, the plastic was in a molten and gooey state (Picture 1), so I laid another piece of parchment paper over the top of the dish and put another baking dish of the same size on top of the plastic/parchment paper sandwich (Picture 2). I then placed a heavy cast iron pan on top of these dishes to apply pressure to the plastic and hopefully compact it tightly (Picture 3). I did this in the oven, but I would recommend doing it on the counter so it can cool faster.If I had any clamps or molds to compact this more tightly I would have, but that just wasn't available to me. After another 15 minutes the plastic was still a little warm, but cool enough to handle, so I lifted it out of the mold. It was much thinner than I had anticipated as all of the air between the small plastic pieces had been pressed out. I put the plastic chunk back into the baking dish and poured more of the plastic from my mason jar on top to build up some more thickness (Picture 4). I then repeated the process I just explained and ended up with a good sized chunk of plastic to work with. I trimmed it up some in the last picture.

Step 4: A Learning Experience

As you may have noticed, the last step was labeled Attempt 1. This is because while my plastic chunk looked and felt beautifully solid after adding the second layer and letting it cool, my knife told me otherwise once I started carving. when taking some material off of the side of the block, my knife sunk all the way into the side of the block. Uh oh. I aggressively cut into the block and found that only a small layer of the plastic from what I added to gain some thickness had melted. The rest of the plastic was tightly compacted inside of the melted material, entombed, but not melted. It may be hard to tell from the picture, but I sliced around the block and opened it like a jewelry box to reveal all of the unmelted pieces.

This revelation led me to rethink how I was going to melt the material more completely on the second time around. Honestly, I think this method with the baking dish could have worked if I had given the plastic more time to melt on the second round, but the depth of the dish and the metal walls made the inside really insulated from the heat. My second attempt went much better.

Step 5: How to Actually Melt the Plastic

Cover a large baking pan in parchment paper and spread your plastic on the paper (Picture 1). Preheat the oven to 350 degrees Fahrenheit and put the pan in the oven. Check periodically if the plastic is all melted (it took around 10 minutes for me). Using THICK OVEN MITTS, take the pan from the oven and fold the parchment paper and the molten plastic in half, doubling the thickness of the plastic. Even with the really thick oven mitts, I could still feel the heat from the plastic quite a bit during this folding, because there was only the mitt and some parchment paper between my hand and the plastic.

In its molten state, the plastic will stick to the parchment paper entirely, so you will need to wait for the plastic to cool in order to separate them. Once cool (Picture 2), you can continue remelting the thicker piece and folding it in on itself until you reach your desired size. For example, if you want a flatter piece, one fold may suffice, but you will need to do many folds for a thicker piece. Remember, it may take a little longer to entirely melt the plastic after each fold, because the piece is thicker and more insulated.

After 3 heats and folds, I ended up with the chunk in Picture 3. Another nice aspect of this method is that you have more freedom to shape the chunk while it is molten. You are kind of stuck to the shape of the baking dish in the first method I described. However, the plastic does not cool under pressure in this method, meaning it may be slightly less dense or have more air bubbles. I ran into a few air bubbles while carving, but they were not too large.

Step 6: Carving the Plastic

In order to carve the plastic, I used the same chisels and knives that I use for wood. It is surprisingly hard to cut, and I had to pound on my chisels with a mallet in order to take off larger pieces at times. It is about as hard to cut as a softer hardwood like maple. The interesting thing about carving in this material is its lack of grain. If you are a wood carver like me, it's kind of a nice change of pace. I've never carved in wax before, but I would imagine it is similar to carving in plastic.

For my first ever carving in plastic, I decided to carve an albatross due to reading Allison Cobb's Plastic: An Autobiography. An albatross killed by plastic waste is heavily featured in this short read that invokes a new way of thinking about plastic. It isn't simply a "plastic is bad for the environment" kind of story, although that topic is mentioned, but a thorough exploration of how plastic defines our culture and legacy. I highly recommend it if you are looking for a quick and unique read.

I carved the body out of my solid chunk of plastic and cut the wings out of the sides of a milk jug. I like how this gives the wings and the body a different look, and it has more of that reclaimed vibe. In order to attach the wings, I used my wood burning tool with an old tip and sort of welded them on. This wood burning tool gets much hotter than the plastic needs to melt, so some of it may have burned in the process. I wore a respirator while doing this melting, but I still would not recommend this method for safety reasons. I will not be using this method in the future.

One awesome part of this material is that you can keep using the material you carve off! Simply gather all of your plastic shavings and save them to melt down the next time you want to make something. It's a process that doesn't require any waste!

If you decide to try this project out, let me know how it goes in the comments below! You can also ask any question about my process if any step is unclear. Thanks for reading!

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    4 Discussions

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    Gruntbug

    6 months ago

    Do NOT try this with wax paper. Parchment paper only. I've done lots of crafts and experiments with HDPE. I need to post some.

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    jgra1156

    Question 6 months ago

    Do you think method 1 would work if you kept it in for longer?

    1 more answer
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    Das Mischjgra1156

    Answer 6 months ago

    I don't see any reason why it shouldn't, and the ability to keep the plastic under pressure while it hardens is definitely an attractive feature of this method. The first layer that I made this way was entirely solid, so I would think the rest of the layers should work the same given enough time.

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    DIY Hacks and How Tos

    6 months ago

    Good idea. I am going to have to show this to my son's class for their recycling unit.Thanks for the idea.