Turn Styrofoam cups into METAL - Experimental metal Casting - Lost foam casting

In this video I experiment with lost foam casting by attempting to turn Styrofoam cups into metal. I used drywall joint compound to coat the Styrofoam and allowed it to dry before dissolving the foam with acetone and then burying the cups in sand. This can be a great way to preserve the detail on foam objects.
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[@robinson-foundry]

I hope you all enjoy this little experiment while I work on more complicated projects/videos. What would you have done differently to make these cups?

[@MeleeTiger]

What if you double stacked the cups nesting doll style so the negative space was slightly larger for flow, and or maybe leave them to soaked instead of pouring the acetone in?

[@SoulDelSol]

* 2 small vent columns next to sprue * cook out the foam residue * preheat the mold Ps: you can dribble sand on mold after each layer (after first few layers) to make mold stronger for above 2 steps

[@rudycandu1633]

You have a couple of issues with the aluminum pour. Fluidity is one. Use a better alloy helps a lot. I don't remember is you said what kind of aluminum you used. It matters for thin casting. Another thing that helps fluidity is a higher pour temperature. The other issue was panic. Your start, stop, and restart in the pour made things worse. You used the word porosity but that wasn't porosity, more like cold shunts and early solidification. As far as your pouring technique. Stop dribbling aluminum into your mold. You need a nice continuous stream.

[@dogsarebest7107]

I'm commenting in the middle of the video, but you had to know that waiting 10 seconds before pouring again means you're not going to get fusion and have a bunch of cold shuts. Remember black sooty smoke is a mold release for a reason.. and your first pour is covered with it. The way you did the acetone didn't get rid of the styrofoam. I'd say probably 90% of it is still IN the mold. You just turned it from expanded foam, into solid hard plastic at the lowest level or underhang by the sprue. Solid, dense plastic that will happily burn and outgas for a long time, because of low surface area:mass ratio (as a solid). Had you poured this without the acetone, it probably would have worked just fine! I've done lost foam casting a few times, and yea.. acetone method is the worst way to go about it. You get solid chunks of styrene in random places, coat the internal surfaces in a thin layer of plastic, etc. Either just pour the metal HOT right into the styrofoam, or burn it out before hand. I'm sure there's a way to make it work, with a vent/drain at the bottom, and large quantities of acetone, so the styrene has a way to flow out of the mold completely. Or just pour hot without interruptions straight onto the foam. Solid styrene (from acetone on styrofoam) turns into a hard, brittle, glass-like plastic that's fairly dense.

[@XXCoder]

Hm I wonder if having cup point upwards and pour on outside route, turning around into bottom of air to fill cup, cop top having air holes so metal can rise. Not too sure how well that would work.

[@sealpiercing8476]

Why not burn out as much foam as possible after clearing most of it with acetone, as in lost PLA casting? As you point out the thin walls are already pushing it so no need to add foam residue as a second complication.

[@TravisFabel]

This is what I was going to suggest. When you melted the styrofoam, you created solid plastic in areas. You could see that in the casting attempt. If you were to burn out all of the styrofoam, not only would it all vaporize as a gas, but it would preheat the mold for when you pour into it.

[@KrazyMitchAdventures]

The problem is, he used Drywall Compound, which is gypsum dust mixed with water. It doesn't do well in extreme heat, so burning it or heating it in a oven, would reduce it back to gypsum

[@bishopcorva]

I was likewise thinking that heating the moulds to burn out the foam would work well, even more so if you used plaster built in layers very thin mix at first then gradually thicker coats in layers. Add in increasing amounts of silica sand then when estimated about three to five millimeters thick. Just heat in the casting furnace to burn em out. Then do not let them cool before the pour. Pour the aluminum while the moulds are still glowing hot. The heat of the moulds will help the metal to stay flowable until the temperature drops to freeze it in shape. After that it's just dunk in water to cool even more and get the moulds to crack from the temp swing shock.

[@bishopcorva]

@@KrazyMitchAdventures hence why I said plaster, as shortened for plaster of Paris. Gypsum while it does contain some likeness to plaster of Paris, it is not the same as. I know how to cast using plaster embedded with silica dust and sand at very high temps, that when quenched the plaster crumbles into a slurry in the quench water. It's a fantastically interesting process and very dangerous to do if you are not wearing protection, since the risk of splash burns is quite high when the just off incandescent mould and metal hits even rolling boil quench water there is quite a bit of stream and lots of popping taking place. So if you do it, be extremely careful and don't stand right on the quench. Long grippers are a very handy tool for that kind of stuff.

[@sealpiercing8476]

@@KrazyMitchAdventures That's true. He would need to use the suspendaslurry stuff.

[@efotube4679]

You can get perfect casting with aluminium too, you have to bake the moulds in an oven to burn out all the styro residue, and cast the metal when the molds are still hot.

[@robiedriscoll6280]

You could try preheating the molds, it give you a little longer for the metal to flow into the gaps

[@Razza2250]

kilning them would get rid of any residual styrofoam/acetone slurry as well

[@anzaca1]

This is something companies actually do.

[@stevebray71]

I was actually thinking that he could do as u mentioned. This would help to take out the poli styrene from the mould but again you would possibly need to be careful about the mould cracking in the heat cycle but it could help to stop the water from the joint compound from boiling so quickly with the water then also causing problems with the mould filling up easily because of the small thickness of the cups same thing really as lost pla if you don't get rid of the pla you have a lot of issues with the mould filling even

[@joejoejoejoejoejoe4391]

It does look like cold lap, something that I have experience of when the metal is too cold when poured, however if the metal is too hot, it's so runny it runs into the sand an you get a sandy casting ( like a casting, but with a metal/sand skin )- not good when zirconia sand is used, it blunts carbide tools like you wouldn't believe.

[@allangibson2408]

Acetone dissolves styrofoam - it doesn’t remove it, it just leaves a varnish of polystyrene behind. Heating the molds to ignition temperature of the polystyrene might help because otherwise you are fighting the combustion gases from burning styrene in trying to get metal into the mold.

[@zumbazumba1]

And there is no gas vent so all the gas is trying to go up,from which you pour metal .And thats why it had so much porosity . Pouring basin and sprue are a joke.

[@Stroke2Handed]

Your level of patience is second to none. Use a propane torch to burn the styrofoam out of the molds, the foam will be gone and the molds will be heated.

[@slimsantilli4476]

Cool! My family has an aluminum foundry. One day a guy up the street brought in a display figure of the Pillsbury dough boy. It was made from styrofoam. We covered it with nobake sand and cast it. He put the casting in his front flowerbed. You did a good job gating the cups. One trick that helps is to run a narrow hole next to the inlet. A "riser" hole to let gas out. A 3/16 rod hole is all you need.

[@aserta]

I think the problem with the first (shown on camera) casting of the cups was the fact that you stopped. You should continue even with there's a flash. It's normal to see stuff like that when you burn lost casting material. The concept worked, incredibly well.

[@ryank8113]

This is a really cool idea and my first thought would be to doublestack the cups. Twice the wall thickness and you could keep the styrofoam texture.

[@THESLlCK]

lean cup

[@MrJeepmarine]

Good Idea, I was thinking that he might do that.

[@presidentjoethudbrandon7074]

Maybe if you preheated the mold to burn out the remaining Styrofoam you could avoid off gassing and fire. Acetone will dissolve the Styrofoam but not remove it. It just turns into slime that takes up far less space

[@Slide100]

What about building a couple of small diameter vents off the rim back up to the top? That would vent the air, you probably wouldn’t get the bubbling, either. Might be worth a try 🤷‍♂️

[@joejoejoejoejoejoe4391]

A bottom fed casting would be even better, allowing the gases to exit through the riser instead of flowing against the flow of metal. On some small castings, spikes are poked through the sand to touch the pattern to give a path for gasses to vent out, and the resulting metal that enters the vent can be easily snapped off.

[@keithyinger3326]

@@joejoejoejoejoejoe4391 I cast bronze coins and thats the method. I use a flat two-part sand mold. Metal goes in one edge of the coin, and I have 2 small air vents at 1/3 and 2/3 position going up. That way, the metal can flow in and push any gases up and out the vents as it flows. It also helps when you're casting things like animals, flat, that have four legs and a tail. Put an air vent at each extremity or it won't fill completely. Those extra small "sprues" are easy enough to cut off.

[@RC-fp1tl]

It’s always a good day when Robinson Foundry uploads! As for improvements, it sounds like removing, not just dissolving the foam would help, slightly preheating the joint compound mold, and trying to reinforce the mold by imitating your suspendaslurry technique by pouring sand over the wet layers or even adding the wire. Inspiring video! Thanks!

[@shannahmiller]

This was really interesting. The pewter cups look really good.

[@boelwerkr]

To cast really thin things in aluminum with the lost form method, you have to heat up the mold. I heat up the mold to burn out the Styrofoam, then pour in the aluminum into the hot mold. With enough head to get the pressure high enough i can cast parts thinner than 1mm. To burn out the mold i put the mold into sand in a metal container, and then heat up everything in a furnace. The the Sand will hold the heat for quite a while. This really helps to get the liquid metal to every part of a thin walled mold. As a mold compound i use clay slurry with soap, sand and rock wool to build up thick and stable shell around the object.

[@jonanderson5137]

Might sound weird, but Id like to see that process.

[@MisterTee2010]

I've been looking at different things to help reinforce my jewelry without damaging it by over heating. I never thought of pewter until now. Thank you for sharing.

[@jerrysanchez5453]

I would have never thought of switching to pewter.very clever

[@Croatilillious]

The drywall joint compound looks really tasty ngl

[@davidward3991]

Very informative. You changed your process from aluminum to pewter and were successful. Thank you.

[@FWPrecords]

The experiment left you with some cool looking cups! I think they turned out good. Never thought I would see a nice metal Styrofoam

[@skumomcbee9280]

When I saw the perfect molding of the styrofoam texture I gotta say I was impressed :)

[@general5104]

EXCELLENT EXPERIMENT !!! In my younger days as a Die-Maker, the shop I worked at, made a pinned together Aluminum mold to inject red wax into. Then open, clam-shell like, and the wax part was removed and close the mold and do it all over again. They would then, coat those with potters slurry and add fine sand, and allow to dry, and layer it many times. Then cut a sprew hole and Fire the mold into porcelain, and pour out the wax. Then pour Stainless Steel in the sprew hole and allow to cool and drop it in a shaker bin with metal BB's and a Stainless Steel part emerges. Cut and dress where the sprew was and have a finished part in a very quick time. It turns out that those were Turrent mounts for Huey Machine-Guns. They were intricate parts. & made from Stainless Steel, it would have been hard to make those. That's kind-of what you're doing here with FOAM instead of "Lost Wax"

[@n.gravey3735]

Stumbled upon your channel a few days ago, and been going through your back catalogue, some amazing projects!!! Keep up the great content!

[@jackstrange186]

Awesome. I would love cups like that.

[@andyroo3022]

Your persistence with your project payed off. The detail of the styrofoam on the pewter looked cool before the polishing,

[@Wrighmachining]

Your a geniouse !!!!! Im trying some of these technics to improve my lost foam casting . Thank you !!

[@demitv001]

@Robinson Foundry could these cups be then used as a mold to do loss casting with aluminium and other high temperature metals?

[@anzaca1]

Probably. The sand etc is what handles most of the heat.

[@lowellhouser7731]

Having done this a few times now - thinner is not a good idea with lost foam. It's a great method for thick blocky things, and in those cases you don't need to melt out the foam because pouring temperature aluminum burns through it just fine as long as your maintain a constant pour with proper gating.

[@tracybowling1156]

Wow! You always make the best projects! I always have such fun when I visit your channel. I'm sure a lot of metal melters learn a lot from you. Excellent as usual! ☺️

[@MeleeTiger]

Cool that the pewter worked out at least!

[@1FishinAddict]

Used plaster drywall to cast foam successfully about a decade ago when I was first getting into metal casting. A very effective coating, cheaaap too. No need for acetone, but do need vents though.

[@aserta]

FIY, you should be able to remove the joint compound with acids. There's specific types used to clean tools of concrete and other work related stuff. I used them to dissolve concrete (or at the very least weaken it) when i hole where i couldn't use a drill to cut. You can basically scoop it up with a spoon at that point.

[@SAOS451316]

thanks for uploading with proper captions, it's appreciated. :)

[@THX..1138]

I remember reading about aluminum casting temperatures, as little as 50 or 100 degrees Celsius can make a big difference in how the metal flows....Casting something so thin the you may have needed the aluminum to be a little hotter and or needed to preheat the mold so the metal stayed hotter longer.

[@SeanBZA]

Paint the cups with some white PVA paint first, to get a layer to interface with the drywall compound. Also try diluting it further for the first coat, and using a paint brush to do a few coats first, before the more thicker coats, and for glueing the sprue on take styrene and dissolve in acetone till saturated, and use a drop of that on the sprue, then touch the cup to there, no glue residue. Acetone will have to be left in for a day or so, but cure the compound in an oven at low heat first, around 120C, so as to try to melt most of the styrene out first, holding so it is sprue down in some of the sand, so the melted plastic can flow mostly out.

[@westcoaststacker569]

Awesome job and demonstration. Now I need a Circle K Polar Pop cup, the foam ones degrade quickly when reused.

[@Daisuken92]

It's always a good idea to pre-heat your molds

[@conrat2000]

Awesome video. Thanks

[@macrumpton]

If you heated the molds and sand before pouring it would might reduce the thermal shock. You might make a few vents as well to prevent heated air from creating pressure inside the molds. When we did a similar process in school we did not use a coating or remove the foam, but let the metal vaporize it as it poured. If we wanted an area to be smooth we would attach some paper to the foam which worked amazingly well. We also used a green casting sand that would hold its shape if you squashed it in your fist and then opened it. You could add all kinds of textures attaching various kinds of tape and paper to the foam.

[@BEMetalMelting]

Super cool! Good job!

[@lyledavis819]

I was thinking the pewter cups would be better with a mirror finish, but I actually like that they took on the texture of the Styrofoam cups.

[@rickhalverson2252]

Drill some very small holes in the bottom of your mold. Cover your sand/ box with thin plastic. Add a secondary box below with vacuum.

[@JohnFourtyTwo]

I couldn't help but think of an old Star Trek episode where they were drinking coffee on the bridge out of Styrofoam cups painted silver.😉☕

[@bastilugauer]

I'd try doubling the wall thinkness by placeing two cups inside of each other, also creates a thicker base and higher walls, but both could be cut off if wanted. Thicker walls get rid of a lot of problems while casting.

[@BEEBO168]

hi dude, i just wanna say thanks for making the videos that you do, theyve inspired me to try and do what you do for a living. Many thanks

[@SantiagoGomez-kx9qx]

You have some great NileRed vibes!!! Awesome content!

[@tracybowling1156]

What an excellent idea! I just love your channel!!

[@patprop74]

just a future suggestion, if you ever find the drywall compound shrinks or cracks too much, you can always make a donut shape on a flat surface, and fill the middle hole with plaster of Paris, then slowly mix the two together, the Plaster of Paris will help stabilize with the shrinkage as the compound dries by accelerating the cure time.

[@Thestongehengekill3r]

SICK! Keep up the cool vids!

[@augustm.moschera8646]

Very cool and original idea! I might have to try this one.

[@derrickstewart8814]

Great idea for an office something to hold pens pencils paper clips erasers or other things amazing work

[@joshuarankin1905]

Thumbnail Award goes to you my guy... 👏🏆👏 Awesome work keep it up!

[@robinson-foundry]

Lol Thank you!

[@Rodolfobia]

that was a great video thanks for uploading

[@sergeantcraphead]

Bro that's awesome 😎

[@NoodlesTheSpy]

Now my lean chalice will be reusable. Thanks, Robinson Foundry!

[@EatRawGarlic]

I recall large scale foundries using additives like very fine silicon dioxide to improve the flow of the molten aluminium. One of the mechanisms by which that works, is by lowering the thermal conductivity of the molten material, allowing it more more time in a less viscous state. Another option might be to use aluminium-magnesium alloys.

[@michaelmuehr8020]

Awesome video!

[@Booniebee]

I love your lost pla vids and the other ones are cool too! Love your vids

[@frankierzucekjr]

I gotta say, the packing peanuts look so freakin cool. The cups came out cool too. Like mini trash cans lol

[@frankdoss6313]

JOINT COMPOUND!!! I should have thought of this! I wonder if purging acetone & styrafoam remnants with a torch would have helped.

[@DaaGoddy]

Try some Ventil tubes. Like smaller versions of your feeder tube. Makes the acetone part easier and it casts much better

[@alanribeiro4504]

Very interesting.

[@darko6697]

that's really cool 😎 👍

[@AddictedtoProjects]

Excellent result! I would be happy with those pewter cups :) I guess you'll have to resort to centrifugal casting to be able to "drive" most of the metal into all the crevices of the mold, if you want to repeat the test with Aluminum. Good luck!🤞

[@dash8465]

See the videos on how small boat propellers are cast in aluminum and stainless. Its basically a dip/coat/dip/coat buildup then kiln dried/hardened to become a ceramic of some sort… your styrofoam cup would vaporize, final clean/rinse/blow it out, then reheat (or pre-heat) to ensure its completely dry inside.

[@unstablenester941]

Great video. I'm playing with casting and I will be trying something like this soon. Would vents for escaping gasses hve helped?

[@3dagedesign]

This is originally known as the "Lost WAX" technique. as used by artists since (at least) the ancient greeks. a wax scipture is created, then placed in sand, then molten metal is poured which melts the wax, allowing the metal to fill the void.

[@buckstarchaser2376]

Try the acetone stage with the cup sprue facing down... Jet it up in there somehow. Perfect this process, as I want to pour myself a styro-sterling cup from which to sip mohitos while I watch F1 recordings.

[@billskinner623]

I love it. Science!

[@DanelonNicolas]

it was amazing hahaha in addicted to your channel !

[@gearsofinspiration8528]

An interesting idea also what's the hox on the desk since it looks lovely? Maybe could make a wood box and cast some fittings for it as afuture project

[@adamturner7436]

I think I have some Pewter in my garage. Said only a few, it's certainly not me...but i was entertained. Thanks for the video.

[@NSResponder]

In industrial lost-foam casting, it's common to coat the foam with refractory plaster and sand in many layers, and then to burn the foam out in an oven before casting.

[@rachelg552353]

Interesting experiment. Styrofoam teddy bear next!

[@bryanpesce1]

A vent tube or 2 may also help with the gassing issue as well as preheating and burning off the residue before hand.

[@jamessalonga3436]

I love the solid aluminum packing peanuts

[@TWLML420]

Great video

[@majoraswrath1417]

Mikey is one step closer to living his dream as a styrofoam cup, yo.

[@h7opolo]

beautiful. subbed

[@bbrachman]

I have seen others create the mold with some kind of water soluble plaster. Then heat (in a kiln) the mold to burn off the styrofoam so you have a completely empty mold.

[@larryphillips4164]

Awesome

[@cameronc1300]

great channel :D one-of-a-kind

[@guillermorobles6381]

I dont know what it is but you are incredible

[@_Turbocat777]

I never knew I needed metal packing peanuts until I heard them clink together

[@Astinsan]

You should try light toping for your coating. It drys in as short as 35 mins. Will make your coating process faster. You can also mix what you need.

[@charizard2650]

this is cool

[@lawrenwimberly7311]

put 2 cups together to increase wall thickness for an aluminum cast... also add a metal tube to the top of the riser to increase head pressure

[@gerardj.lesperanceiii1238]

just like to know could you use them to drink hot or cold beverages from them or do you have to use a different kind of metal

[@sebastienc8797]

Hello. You should definitely try Zamak alloy to do this kind of things. It's really "pour friendly" and has amazing results compared to aluminium !

[@milolc]

Couldn't you preheat the mold? You would probably need to do a different style mold, but if it is already hot when the metal is poured there would be plenty of time for the metal to flow into all the little cracks and crevasses before the whole thing slowly cooled.

[@PBRJOHN684]

Could you Try the Suspend slurry and burnout cycle to make the cups?

[@willhutton1516]

You should try and see how useful a metal version of those styrofoam food trays are.

[@lenux21]

what alloy is ur pewter currious if it is lead free and safe to drink from

[@randyjenkins8896]

thanks i finally discovered what alloy is pewter.

[@haydenc2742]

wait...is that drywall compound like suspend-a-slurry?? Could it be used by coating with the silica sand and making a mold for other things?? Also I am wondering if it could be heated like the suspend-a-slurry and silica sand in the kiln...

[@joshmellon390]

All the comments about burning out the film thin layer of Styrofoam residue like it would make a difference lol. Great idea with the acetone, I'm going to use that this week.

[@WendysAnime]

Awesome, you could try 3d printing a thicker cup and making a mold from it, I'd totally buy something like this!

[@THESLlCK]

those packing peanuts are SO DETAILED

[@kursor6127]

Great idea. First attempt could work but You need to pour faster. Not from crucible but useing spoon that you'll empty in 1 seckond. But to pour so fast plaster cant be saturated with disolwed foam- to much gases.

[@incandescentfennec6916]

Here's a tip, if you plan on drinking out of those cups (for whatever reason) avoid putting acidic drinks in them. Especially tomato juice. The acids can react with the metal and form toxic compounds. Could be a clever way of poisoning someone...

[@BariumCobaltNitrog3n]

Instead of drywall mud try Durham's water putty. It sets very hard and will form intricate molds. It sets fairly fast and even thick layers will set overnight. It seems resistant to heat but I haven't tried molten metal. You mix the powder with water to make a consistency anywhere between firm clay to pour-able liquid. Non toxic, no smell, very cheap.