Designer Vases From Used Coffee Cups

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About: Analog maker dabbling in digital manufacture

Styrofoam cups are light, cheap, and insulating, but flimsy and rarely recycled. Here's a way of transforming a used styrofoam cup into a similarly-sized vase of your own design. It costs nothing, only takes a few minutes, is ridiculously easy to do, and every vase/pot will be unique. It's an interesting gift if you add flowers or a small plant.

Step 1: Materials and Equipment

This simple project uses equipment that will be found in nearly all kitchens. I used a slow cooker, but a pot with a lid would work fine too, I imagine. You also need a small bowl and a rubber band. And a styrofoam cup ($2 for 50, but repurpose a used one if you can).

Step 2: What and How

Styrofoam is a brand name for expanded polystyrene (a hydrocarbon polymer blown full of gas). Put a styrofoam cup under high pressure and/or heat and it will shrink dramatically as the gas is driven out. You can do this by putting the cup in a submersible ROV and sending it 1400 m underwater, or much more easily, by popping one in a pressure cooker for half an hour - you'll get a neat miniature coffee cup. It's cute, but not much good for anything (espressos?). The photo above shows how when you heat the coffee cup, it first expands, then shrinks smaller and smaller the longer you leave it. It also gets somewhat distorted, because the plastic gets quite soft. I did these in the slow cooker, but you get a more perfect little cup in a pressure-cooker (see the second photo - it's also faster).
Whether you're making tiny cups or making funky vases of your own design, get the cooker up to heat first (on high). It's also important to cook the cup bain marie style, i.e. inside a bowl that is immersed in water. Otherwise, you'll just melt the cup and make a stinky mess of your cookware.

Step 3: Sculpt a Vase

We're going to take advantage of the fact that in the first few minutes in the slow cooker, the cup both softens and expands. This behavior can be manipulated by applying a constant force to some parts of the cup, making it collapse inwards instead.
Take a coffee cup, and put a rubber band around it near the top. Put it in the bowl, replace the lid, and boil for a couple of minutes (watch it, don't time it!). Remove once suitably shape-changed, and take off the rubber band. Done!
Try putting two bands on, or put an odd-shaped object inside to act as a mold (I ran out of used coffee cups, so haven't actually tried the latter). This project is great for experimentation to see what effects you can achieve.
Tip: get the rubber band as tight as possible. Strong, tight bands will create the most interesting effects.

Feedback
COASTER19 advises that if you have a pressure cooker, you get best results from looser bands, with the cup upside down, and a 7-minute cooking time.
Valaynetine reports that some sorts of polystyrene cup don't change shape at all. The ones I tried - all the same sort - were a soft, relatively bendy type of cup, so that's probably the style to use.
calischs from InstructablesTV made a short video based on this instructable, and cut the rim off then immersed the cup in boiling water with the help of a metal weight. It seemed to work well. Check it out, it's only 46 seconds long!
rojo.balloon made a styrofoam hat from a bowl.
Maurice1985 made an instructable (and made lots more vases than me!) showing how you can fill these with concrete to make a more permanent vase.

Step 4: Add Flowers

With flowers or a small plant, you have a nice inexpensive gift with a unique twist. I think the plain white vase is interesting enough on its own, but it is also a blank canvas for your own creativity. It would be great to see variations on the theme, so if you make one, please post a picture in the comments section.

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    94 Discussions

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    NikkiDread

    4 years ago

    When I was a kid we used to decorate the cup with markers first then put it in the oven. we made small hats for dolls with them for 4th of July

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    makendoNikkiDread

    Reply 4 years ago on Introduction

    Neat. How long did you put them in for? How small did they get? You should write it up, sounds fun.

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    MYT CR8TiV

    5 years ago on Step 4

    Will this work in a regular like soup pot with a lid ? My husband always brings home Styrofoam cups from work and I always wanted to find ways to craft with it. This seems interesting enough to try.

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    makendoMYT CR8TiV

    Reply 5 years ago on Introduction

    Sorry for the *really* slow reply... yes, it would work fine. calischs made a video instructable which showed it working just by dunking a weighted cup in a boiling pot of water.

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    shortone

    5 years ago on Introduction

    Great idea! I have once concern though: I know that melting styrofoam is super toxic, which is why it is a very bad idea to use a wire cutter on styrofoam at all. Do you know anything about the toxins released by heating it up in water? I don't know myself, but I'd definitely want to research it a little more before I melted too many cups! :)

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    makendoshortone

    Reply 5 years ago on Introduction

    Probably the same amount of toxins released as when adding a hot coffee to the cup, i.e. very little. The water is at 100°C or just above, and while it's clear the air in the polystyrene is driven out over time as the cup shrinks, that's all you really need to worry about. You're not melting the cup.

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    kathyhibbert

    6 years ago on Introduction

    Oh my! I'm glad I didn't miss your instructable. The heading~what to make with garbage~almost put me off. Garbage or trash. Food or other. This is one our grandson and I will definitely try.

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    taria

    7 years ago on Introduction

    these are pretty cool, to bad spray paint eats them up like candy, cause if you added some of that textured spray paint to them they would look like little stone planters...oh wait, when they are shrunk down you think spraying them with paint would still eat them since they aren't so 'puffy' anymore?

    I won't be able to try this cause my mom would kill me if I used her pressure cooker for shrinking down cups. I know I feel like a 4 year old when I'm not. Might have to just go out and buy my own just to try this. :)

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    makendotaria

    Reply 7 years ago on Introduction

    I suspect the shrunken cups will still get chewed up by the spray paint.
    It is a pretty frivolous experiment, to be sure, but I think you're overestimating your mom's reaction. She's more likely to think they're cute than be driven into a homicidal rage... but I don't know your mom. :)

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    Treknologymakendo

    Reply 6 years ago on Introduction

    Yes. The solvents in the paint will still eat the styrene. Your choices are model making paint (maybe) or acrylic paint like that found in Primary Schools.

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    tariaTreknology

    Reply 6 years ago on Introduction

    good idea, I didn't think of acrylic paint. thanks for that.

    and makendo, my mom would have a cow trust me, so I will do this at my own house with my own pressure cooker...lol

    Sooo, soo cooool! I have too much stuff around, so I probably won't try this for a while, but what a great idea!!!!

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    corinalex

    6 years ago on Step 4

    Cool! My daughter and I will be recycling lots of cups this way. Thanks.

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    KwartzKitten

    6 years ago on Step 4

    This is adorable and I can't wait to try it.

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    raviolikid

    6 years ago on Step 4

    Do you know how long it takes water to boil in a slow cooker? Or, could I use a pot on a hot plate? I think this is an interesting project for my students in my Arts and Engineering Clubs. I like the maker who make concrete forms with them. We might try that, as we are studying concrete in the fifth grade group.

    Thanks!