Instructables
Picture of Designer vases from used coffee cups
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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.
 
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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.
ikurniawan26 months ago

very nice

NikkiDread11 months 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
makendo (author)  NikkiDread11 months ago
Neat. How long did you put them in for? How small did they get? You should write it up, sounds fun.
MYT CR8TiV1 year ago
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.
makendo (author)  MYT CR8TiV1 year ago
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.
sabu.dawdy1 year ago
how do u doooooooo this shuff.. its awesomeeeeee
It's called... Read and find out
hahaah
shortone1 year ago
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! :)
makendo (author)  shortone1 year ago
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.
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.
taria3 years ago
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. :)
makendo (author)  taria3 years ago
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. :)
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.
Wonder about a Sharpie?
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!!!!
corinalex2 years ago
Cool! My daughter and I will be recycling lots of cups this way. Thanks.
This is adorable and I can't wait to try it.
raviolikid2 years ago
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!
makendo (author)  raviolikid2 years ago
Pot on hot plate will work fine, as long as you have a lid.
Great! I have lids!

Thanks for your reply and for the cool Instructable with the great links! I mean, your directions were great - but adding the links was a nice bonus.
goes great with the "coke can flower"
csantiago33 years ago
This is very cool, now to find syrofoam cups!!
I had no styrofoam cups so I used a styrofoam bowl. I put only one rubberband and it came out to be a hat after 10 minutes. :) Here is what they look like
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makendo (author)  rojo.balloon3 years ago
Nice styrofoam hat! Thanks for posting the pictures, good to see it works for bowls too.
This is a pretty fancy idea :0) I will definitely be trying this! Thanks so much for taking the time to share this unique technique. Have a wonderful day ^.~
makendo (author)  TheNailDutchess3 years ago
You're welcome, & good luck.
WhyHello3 years ago
I'm curious how did u get this idea :)
makendo (author)  WhyHello3 years ago
I knew that you could get a miniature polystyrene cup by pressure-cooking it. I wondered what would happen if I used a slow cooker instead, and the rest was just messing around...
WhyHello3 years ago
I wonder if you can use a microwave
makendo (author)  WhyHello3 years ago
Probably not. Microwave ovens work their magic on water, and a styrofoam cup doesn't contain much. However, if you added water, put bands on the outside, and cooked it for a minute or two, who knows? You should try it :)
ellequoi3 years ago
Neat! I wonder how these would work as little planters if you poked holes in the bottom. I'm kind of concerned about the chemicals that would wear off on the pot as well... maybe this would be something I'd try with a reject pot, or a crockpot with a liner added.

Also, would dye in the water stain the cup for you?
makendo (author)  ellequoi3 years ago
Thanks. They work just fine as planters, but they're kind of an awkward shape.
Any leaching of blowing gas, assuming there is any left in there, will be minuscule - you'd expose yourself to far more toxic chemicals by eating any blackened piece of food. Or a peanut. Or an apple seed. Or lighting a candle. Or painting something. Fortunately, we have all sorts of clever mechanisms for scavenging small amounts of toxins out of our system - just as well, or smokers would have to worry about a quick death from cyanide poisoning as well as a slow one from cancer. The gas used to foam polystyrene is volatile, so if you want to be super-cautious, just do it outside. It won't stick to the pot.
Any dye that dissolved in the water would not stick to the cup, unfortunately.
Bunchland3 years ago
We loved this idea so much we thought we would share it with our readers as well.

http://www.bunchfamily.ca/valentines-day-craft-styrofoam-vases-paper-flowers
makendo (author)  Bunchland3 years ago
Thanks for letting me know - good idea to include the video.
I was wondering if you could manipulate the shape even more by putting the cup on a turntable/lazy Susan and using a heat gun. Then, you could heat the cup in specific places. I have one for heat embossing when I rubber stamp.

If I get hold of any styro cups, I'll let you know what happens.

Suzanne in Orting, WA
I know that styrofoam melts almost instantly against the tip of a hot glue gun (personal experience) so it might just create holes in the cup.
I'm sure it would melt the styrofoam if it was held too closely, especially if it was a industrial strength type gun, but the one In have is a basic rubber stamping type and I think if enough attention in paid to the distance, it will be do-able. In fact, I never thought about using the the heat gun to melt holes in the foam. It could be an interesting addition to the textures.

Since I have sheets of foam, I was thinking about cutting them in circles and using the gun to raise the edge of the blanks to create "plates".

Thanks for the additional ideas!

Suzanne in Orting, WA
makendo (author)  Suzanne in Orting3 years ago
Interesting idea; don't be surprised if your cup goes all Salvador Dali on you! Good luck, I look forward to hearing about the results.
annab1353 years ago
Could several be combined in such a way that a larger vase could be made?
makendo (author)  annab1353 years ago
Hmm, interesting, I'd never considered it. Are you imagining, say, a triangle of three or a stack of cups? For the triangle, you might get some unusual effects, but I doubt they'd hold together well unless you left the band(s) in place or glued them. The stack could look really crazy - I hope you try it!
sitzikbs3 years ago
totally awsome idea! its even great for recyceling!
Valaynetine3 years ago
I attempted this, but all I had on hand was those stretchy, rubberband like hair ties, the "no knot" kind, not sure if you're familiar- but nothing happened with the styrofoam cup. Does the type of band I used affect that? I don't see how it would, but after trying about five times, using various levels of boiling water, a crock pot, rice cooker, and a stainless steel stock pot.
makendo (author)  Valaynetine3 years ago
I really can't see why the band would matter - anything tight ought to do it. I wonder if it is the type of polystyrene cup, though - some may be more heat resistant or stronger than others. When you say nothing happened, did the cup at least shrink (even if it didn't change shape)?
The only other thing I can think of is the temperature - this trick works best if everything is really hot before you start (i.e. the pot should be boiling). Otherwise, it will take a long time.
All the cups I tried were the same sort - quite a soft polystyrene, bendy and not brittle. Maybe the more rigid style of cup doesn't work so well. If you could possibly post a picture of the type of cup that doesn't work, that would be really helpful. Thanks!
It could be the type of foam then. The water was boiling pretty heavily, but the cup neither shrank nor expanded, even when left in there with there lid on for about ten minutes. I'll try with a different type of styrofoam, thanks again!
xKari3 years ago
This looks really awesome! when i told mum about it, she got concerned about the chemicals from the cups though =X
makendo (author)  xKari3 years ago
Thanks!
Promise her that you won't eat the cup.
xKari makendo3 years ago
lol i was referring to when you heat the cups =P
makendo (author)  xKari3 years ago
Yeah, I know, but I won't try and convince your mum it's safe (even though it is). Next time, ask for forgiveness rather than permission :)
xKari makendo3 years ago
lol but i have to because it's her kitchen XP
makendo (author)  xKari3 years ago
Fair enough :)
xKari makendo3 years ago
and equipment
COASTER193 years ago
I love this idea. When I tried it, I found that it worked better with a less tight rubber band, the cup upside-down, and in the preassure cooker for 7 minutes. I dont know if it was my cups, but when I put them in the preassure cooker with a fairly tight rubber band they were crushed.
makendo (author)  COASTER193 years ago
Glad to hear you tried it, & many thanks for the tips, that is really useful to know - I'll add your advice to step 3. A pressure cooker gets a lot hotter than a slow cooker, so your results make sense. Post pictures if you can!
ricerock3 years ago
Do you like place the cup upside down in the bowl and is there no water in the bowl please answer me I am very excited to make one!!!!!
-rice rock
makendo (author)  ricerock3 years ago
Water in the slow cooker. Bowl is empty. Put cup in right way up (see 3rd photo in step 2 for what it should look like before you put the lid on). Make sure everything is hot before you start and the rubber band you use is tight. Good luck!
jen77143 years ago
Great instructable! I do have a question though. Can you substitute a rice cooker for the slow/pressure cooker?
makendo (author)  jen77143 years ago
Thanks. I suspect that anything with a lid that can boil water would work, so give it a try (I've never used a rice cooker to cook rice, much less polystyrene cups). Just make sure everything is up to heat before you put in the cup.
(and congratulations on the eclairs!)
jen7714 makendo3 years ago
Ahh okay. :) Thanks I'll definitely try it out. These cups look pretty impressive so I was thinking of making some for a centerpiece. Can't wait to try it!

And thank you so much! You too on your runner up finish :)
deladybex3 years ago
Hi Ilove thisw idea but have to ask if the plastic gases that are leaving the pressure cooker are haealthy to bearthe in? Ihave to be extra careful with plastics and heat in any form.thanks
makendo (author)  deladybex3 years ago
Well, because you're just putting the cup in the bain marie for only a few minutes, the vast majority of the gas remains in the foam (that's why the cup expands). Of all the experiments you might do with plastic, this must be one of the safest! Also, the gas they use to foam the polystyrene beads is pretty benign anyway - you'd undoubtedly be exposed to worse when filling your car or lighting a fire, neither of which are particularly risky activities.
Thanks. This is a beautiful Instructable. The photos are lovely and the idea is original. I'm always looking for more ways to upcycle foam cups that come into my house. Where I live the city does not recycle this type of plastic. It's up to the individual citizen to locate (and deliver to) a private company for recycling.
makendo (author)  sparkleponytx3 years ago
Thanks. They don't collect expanded polystyrene here either - too bad, because it's relatively easily recycled, just hard to transport because of its bulk. Good luck with the upcycling!
poppet23 years ago
Thanks for clarifying. My eyes (as well as my brain and body) are old. I don't trust them entirely.
I'd like to try this. Sounds creative once you got the hang of it.
makendo (author)  poppet23 years ago
Good luck; let us know how you get on.
CrLz3 years ago
Elegant, both your designs and your Instructable. Great post!
Duckism3 years ago
I think it's great to make these into just sculturs or soemthing, instead of a vase because it will just leak every where. have you ever left a cup of coffee or tea over night in these kind of cups? the next morning you'd see beads of coffee on the side of the cup. so it can't really be a functional. poeple are green washing this project a little too much. espeically if they want to coat the cup with different kind of spray and stuff making this easily recyclable polystyrene cup into soemthing that can't be recycle any more.... how is that green? it would just be much better for the environment if you simply put the cut in a recycling bin.
makendo (author)  Duckism3 years ago
There is no need to paint it to make it waterproof - it's every bit as watertight as it ever was. These vases have had water in them for a week or so and are as dry as a bone on the outside. While the expanded polystyrene is mostly air, it's watertight by virtue of its hydrophobicity - the polar water molecules aren't in the least interested in interacting with the polymer, so they don't penetrate the cup in the slightest. I only suggested painting it for decoration; it is completely functional without.
poppet23 years ago
Another question. If the cup doesn't have water in it, how does it remain upright? I can't tell what has water in it and what doesn't.
rat3 poppet23 years ago
I believe he is saying to put water in your slow cooker pot; float a dry metal bowl in the water; Then put the coffee cup (no water in it) in the dry metal bowl. Similar to a double boiler when melting chocolate. Very cool. Great for Xmas gifts. Thanks!
makendo (author)  rat33 years ago
Exactly correct!
nejo00173 years ago
really nice reuse!!!
lotusduck3 years ago
To me these seem like super tiny lampshades.
makendo (author)  lotusduck3 years ago
They do, don't they? :)
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weibbed3 years ago
This is very clever and will be fun to try.

Just a note though: foam cups are NOT Styrofoam. Styrofoam is a trade name for a different product and it is not used in foam cups or meat trays or any of the numerous other food related containers that people call Styrofoam. Mostly it is used for insulating house and occasionally in craft products.
makendo (author)  weibbed3 years ago
Thanks, and yes, you're quite right. However... it's tricky whenever a brand name becomes the default name for something, so I tried to both call the material by its common name and explain that the material used is actually expanded polystyrene.
poppet23 years ago
Does the styrofoam cup contain water? Is the bowl in water as well as filled with water?
hammer98763 years ago
Kudos for being featured!
Applebohn3 years ago
I love it!!!
Honus3 years ago
That's great!
Puzzledd3 years ago
This is great - very clever: cheap, green, easy, novel and cute... and an appealing gift! Thanks for the idea :)

makendo (author)  Puzzledd3 years ago
Thanks!
foobear3 years ago
pure brilliance!
karlpinturr3 years ago
Nice - they remind me of the (almost) craze for forming old vinyl records into dishes & stuff.

when I got the 'subscription update' notification, I thought they needed painting, but looking at these end results, I'm not so sure they do (unless you're going for a very smooth and/or glazed look). And I'm pleasantly surprised how well the cup/vase and lillies(?) proportions work.

Early on, you showed how the cup expands a little to begin with - would it work if you stopped heating it at that point, for a slightly larger vase?

Does the process destroy the ex-cup's liquid-holding ability?

And if you can still find non-biodegradeable cups, would they last forever without painting/clear-coating, etc.?
makendo (author)  karlpinturr3 years ago
Thanks. I think the cups have been caught at the slightly expanded stage, because the 1-band one is the same height as the original despite the fact the lip has been folded down. I'm sure it could be optimized better though, because the two examples were the only ones I did. The cup is every bit as water-tight as the original, and it ought to last a long time if you keep it out of the sun and are careful with it. And in some ways it's more robust than a ceramic vase - it would probably hold up to being dropped better, that's for sure!
Wow, they are wonderful!
gonal4 years ago
Great idea!

Just one question, would it last long?
makendo (author)  gonal4 years ago
Well, probably not - it is just styrofoam - but I imagine at least as long as the flowers!
reedz makendo3 years ago
It could potentially last a lot longer with a coat of clear-coat over the finished product.
makendo (author)  reedz3 years ago
I'm not so sure that painting it would make it much stronger... maybe if you slapped it on really thick? Couldn't do any harm, anyway, provided it was water-based.
If the foam will take it as a coat without melting / deforming / whatever, there are a number of good spray acrylics or enamels that are very waterproof and last a long, long time. Dip the cup in a standard primer to seal the pores - now you have an even surface if you want to color the vase. Most of the spray brands have a great color selection, too.
kelseymh4 years ago
What a great little project! Clearly and engagingly written, with wonderful photos of steps along the way.

I have one small suggestion. The photos in Step 3 seem to be somewhat out of sequence. You might consider rearranging them in an order more like

-- No bands
-- One band at the top
-- One band after cooking
-- Two bands (top and middle)
-- Two bands after cooking
-- Mouth view

That seems to be a more logical flow.
makendo (author)  kelseymh4 years ago
Thanks - you're probably right and I've reordered it.