Introduction: How to Make Super Cheap Strong Castable SULPHO-PLASTIC

Picture of How to Make Super Cheap Strong Castable SULPHO-PLASTIC

Ok, I have recently done some experimenting with mixing LDPE and sulfur, and to my suprise, the result is a very tough, stiff material that is much much stronger than the original LDPE. This stuff is amazing, easy, and extremely cheap to make. I have updated the instructable to include the steps for making this LDPE sulfur plastic.

If you use no LDPE, the sulfur comes out brittle and crumbly, so it is useless alone. However, you can mix it with aggregates such as sand and gravel to make a very stiff and fast drying cement.

Step 1: Materials

Picture of Materials

List of materials

1. Sulfur- can be powder or pellets or anything that is plain elemental sulfur. You can get this at a farm supply store. I got 50lbs for $30. It can have impurities up to maybe 20%. More impurities equal less strength. If you don't want large quanities, buy some from here>

2. Aluminum foil- optional- I got this at Cosco for $15 for two rolls. This comes out to be 5 pounds of aluminum. If you don't want large quanities, get a roll from the 99 cents store. This is used as an aggregate.

Edit: I found Aluminum foil to be a great aggregate, but you can use other things like rocks or sand to make it stronger. Also, try painting the sulfur directly onto some fiberglass and layer it like a surfboard. I find that makes for a very strong sheet of plastic. Just make sure you get the sulfur down into the cracks because it dries quick.

3. LDPE - get this either from recycled plastic, such as milk bottle caps and other flexible lids, or online here>> 
or here>> 
this comes out to about 7 cents per cubic inch, or 2 dollars per pound.

Total costs-
75% LDPE + 25% sulfur- about 1.70 per pound
25% sulfur + 75% aggreagate (sand and rocks)- 0.15 per pound

**all percentages by weight***

Step 2: Instructions

Picture of Instructions

Sulfur + LDPE-

First heat up the sulfur in a pot until it is smooth and all the chunks are gone. Keep it a little hotter than its melting point.

Then once the sulfur is melted, add the ldpe scraps/ rod. They will form a large glob in the sulfur. Do not add ldpe until all the sulfur is gone because you want the heat from the pan to be spread out evenly and not burn the plastic.  You do not need to measure the amount of sulfur or ldpe, because the excess sulfur will be left in the pan.

"Knead" the plastic with a spoon so that the plastic is thouroughly integrated with the sulfur. Fold it over itself many times, and also cut into it letting sulfur flow in.

Once you think you have mixed it well, take the glob out with a spoon and press it into your mold. It should only take a minute or two to dry, then take it out.

Let it sit for a day before using it! The bonds between the sulfur form very slowly, and playing with it will ruin it. After that, you will have a hard, almost metal like peice of plastic!

Sulfur + aggregate

Do pretty much the same thing as the ldpe, except put in rocks and sand instead of ldpe. Use 75% rocks/ sand, and 25% sulfur. The rocks and sand will cool off the sulfur and make it take forever to melt down again, so be patient.

Aluminum granules can also be used in place of rocks and sand. Just use an old blender to chop up the aluminum foil in water, then mix the granules in with the sulfur.

pour it into the mold and let it cure for a day.

Step 3: Experiment

Experiment! Try using ldpe, sulfur, and aggreagate and see how that turns out. Try making it conductive by adding copper. The best thing about it is if you screw up, just remelt it and pour again!

Step 4: Make Some Awesome Stuff!

Make some awesome stuff and email your finished pictures to me at I will post them on this page.  Also if someone could email me some properties of this plastic like tensile strength or shear strength, that would be great. I don't have the equipment for that kind of testing. Also, subscribe!


dtrystman (author)2016-03-12

I want to try this to make my own mat tracks for wheeling. How would you recommend doing a large item about 3 feet long? Any way to melt all and poor? Or would doing it little by little be ok or would that nak3 it weak?

shizumadrive (author)2014-01-21

For the teeth molds find an orthodontist and he'll tell you the alginate stuff he uses to make mouth molds/impressions. My dad was one and I don't know what the mold stuff was made out of but it was safe to be in your mouth. They filled the mold with plaster which isnt what you wanted but the mold making itself there is some good stuff out there. Have no idea how much it costs I got it for free.

me35 (author)2012-08-14

Great ideas. I was looking for someone to create a cheap durable and self leveling compound for my wood floor. I don't like the concrete idea but if someone could come up with a self-leveling type of plastic that would be durable and self adhering to plywood i think they would be on the market for big money!

alz19 (author)2011-06-01

nice instructions I am inspired to try them.Just one question.Any idea how to make the sulpho plastic of a particular color like dark brown,red etc

donkeyot (author)2010-08-16 is quite interesting and if you check out the formulas and other tabs one show where you can buy this type of stuff from and how to mould it. Sulphur has many unusual properties its used as a plasticizer to rubberise plastics and increase the wear and tear properties of tyre rubber. Quenching makes it brittle and hard, slow cooling makes it highly rubber ( like those small rubber balls that bounce forever all over the place). Graphite has a ring structure that can form very strong bonds, glycerine too, (dont make nitroglycerine though) and benzene rings like found in toloune again dont add nitrogen or pressure or allow to boil. If you drop some and it exlodes walk gingerly to a bucket of water and pour it in slowly. Benzene rings are very stable and form very strong bonds for plastic, but usually reuire a catylist and appropriate strucural alignement, ie 1-3, dihydrosulthobenzene, would form chains. with an ethylene molecule. 1-3 dihydroxybenzene, something like that anyhow. As i say check out the above website they also tell how to make different plastics out of common ingrediants. Hope this helps

servion (author)2010-06-16

Can I melt this in high detail molds?

galaxyman7 (author)servion2010-06-21

Yes you can pour it into high detail molds. The sulfur will fill the fine detail. The hard thing is getting the stuff out of the mold. It sticks to most things. Try car wax, that seems to work well to keep it from sticking.

sethy89 (author)2010-05-03

Hey man that's an AWESOME instructable! It might be just what i was searching for...
but I need to know a few things about the results of the sand, ldpe and grafite(case you or someone have tried):
1. did any piece got brittle over time?
2. wich resists more to tensile strenght and which was the lightest?
3. i've read that this plastic is inflamable... but how fast it burns?(I mean the final plastic not the mixture)
4. can u give me some relation between weight of the mixtures to the volume of the resulting plastics?
5. someone said the plastic reverted to powdered sulfur... it happened to any of your pieces?(i believe it happened cause he hasn't used any addictive, but maybe i'm wrong)
6. what kind of sand you used? crystaline, red...?

galaxyman7 (author)sethy892010-05-03

1. No, the plastic does not get brittle over time, I think the sulfur actually cross links with the polymers like Qcks said.
2. The mix between just LDPE and sulfur will give the lightest material. I have not tried mixing it with sand, and really don't think it will do anything.
3. the plastic is very slow burning, but once it is started, it will keep going. It is pretty hard to light it though, it won't just catch fire easily.
4. You can't really control the amount of sulfur per plastic, you just melt some sulfur and mush the glob around in it, and it will absorb the right amount.
5. It has never reverted to powder, I am pretty sure the sulfur is in its lowest energy state in the plastic. I have pieces that are a year old and have not changed.
6. I have not tried sand yet, you will have to experiment. Also try fiberglass layers. You can get fiberglass cloth at the hardware store, they sell it for repairing cars.

sethy89 (author)galaxyman72010-05-04

Thanks for the help! I'll buy the material and send you the pics when i finish it

m0tkid (author)2010-01-22

 Hey dude this is really awesome. I have a few questions though (and I apologise if they've already been answered, but i looked - honest!)

1) can it be sanded/drilled/cut
2) if you do the chemisty, does it work out to be an actual polymer?
3)Either way, what is the chemical composition of the sulfur matrix that you 'embed' the aluminum in?


Ps. If i make some in the future I will email the materials science lecturer from my uni and see if I can run a tensile/rockwell hardness test on it. =)

Qcks (author)m0tkid2010-02-26

There's a few things that could be happening considering Liquid Sulfur reacts with aluminum, and it might react with graphite, depending on conditions and exact structure, however... i think this is just a sulfur reaction.

Assuming the information provided by the Wiki is correct, heating up and quenching your liquid sulfur would result in a stronger product.

With regard to adding graphite, it's possible that you get a bit of cross linking occuring between the carbon and sulfur, but that scenario largely depends on the shape of the carbon molecule.

Rather then using aluminum foil or graphite, I think people might get a good result with using finely chopped up plastic shopping bag. Plastic shopping bags are mostly polyethylene, which i believe can cross link with hot sulfur.

m0tkid (author)Qcks2010-02-27

Qcks, I was under the impression that the sulfur acted as a matrix and the graphite and/or aluminum was acting as an aggregate - much like blue metal in cement to make concrete.

From what you are saying you believe there is some actual chemical bonding occurring between the sulfur and the additives?

- I agree with you on the polyethylene - being a thermoplastic it should melt down with the sulfur and chemically bond/interact with it.

I am not a chemist/chemistry student though so I am not exactly sure if my thoughts are on the right track... Feel free to set me straight

Qcks (author)m0tkid2010-03-07

Sorry bout the speed on the reply... I get distracted easy.

With regards to what's going on in the actual finished product, I'm not 100% certain. I'd need to conduct a number of tests to know for sure, and it's more then a little outside my means.

What I do know for certain though is that Sulfur is fairly reactive and undergoes a number of processes which are pertinent for the average DIYer (since the average DIYer probably doesn't have vacuum chambers and such). It reacts with oxygen, water, and is a favored reagent for this reason. 

In organic chemistry sulfur rings, which is likely one of the forms produced, are used as a crosslinking agent (meaning it can bond two plastic polymer molecules), hence why I suggested using polyethylene.
As for a reaction between graphite, Graphite is very plastic like, which is why I think there maybe an actual reaction that takes plasce there, but, as I said, I'd have to look into it more. The type of graphite used (crushed lubricating graphite) probably changes this.

As for Aluminum, Unless it's an algum or a protected type of aluminum, the sulfur wouldd react with it to form a sulfide. After looking at it a bit more, aluminum sulfide readily reacts with water to give aluminum oxide and Dihydrogen sulfide... so there's not as much worry about distortions resulting from the reaction because aluminum oxide is pretty durable, but a slow release of hydrogen sulfide might be an issue.

Any way... this is just what I know... experiment an see how it works

galaxyman7 (author)Qcks2010-02-27

Wow! I just melted some sulfur and put in some LDPE. I mixed it together as much as possible, then took it out of the sulfur. This stuff is amazing! I can't bend it at all, yet it isn't brittle either. The piece I made is probably only 1/4 inch thick yet there is absolutely no bending! It is almost like metal! You guys should really try it! I will update the instructable.

galaxyman7 (author)Qcks2010-02-27

That is interesting, you said aluminum reacts with sulfur? Do you know the chemical formula for that reaction?
Meanwhile I will try some different types of plastic and see how that goes. I think LDPE would work best because its melting point is below that of sulfur's. I will probably use some scrap milk bottle caps.
Also, recently I have found that increasing the aggregate to around 75% volume seems to be the best. I used sand and gravel and it turned out great.
Only problem is that it cannot be machined with the rocks in it, so it would have to be poured into a mold. I will try a mix with only sand and see how that works.

galaxyman7 (author)m0tkid2010-01-22

-It sands very easily, but cracks when drilled. I'm guessing you could cut it with an angle grinder, but I haven't tried.
-I have no idea what the chemistry is for this. It seems to depend heavily on how long and how hot you heat it. I have had very weak mixes of the stuff and very strong mixes. I think the crumbliness comes from getting the sulfur too hot.
- If you could figure out the chemistry, that would be awesome. I don't even know if graphite does anything.

One more thing- I think the material could be milled with a sharp bit or sanding bit, so you could make a mix of pure sulfur, pour it into a sheet, then mill it out.

fuzvulf (author)2010-01-21

 You could probably increase strength using bits of fiberglass pulled from the "itchy" pink style of insulation and mixing it in with your concoction.  I have a set of old books that has something similar to this but without the graphite and using babbit or "white metal" shavings to cast shapes.  fun instructable. 

galaxyman7 (author)fuzvulf2010-01-22

That is very interesting. What is the recipe in the book?

By the way, I have experimented with putting different materials in with the sulfur, and it cools the sulfur down too much for you to be able to mix it in after it is melted. I wouldn't recommend heating up the pink insulation with the sulfur either.

galaxyman7 (author)2009-09-30

This stuff is actually pretty useless except for concrete. I reccomend using recycled HDPE instead of this "plastic". I will take this instructable down.

galaxyman7 (author)2009-05-28

By the way, If anyone has any ideas for increasing the strength more please post them here.

Pazzerz (author)galaxyman72009-05-29

I wonder if aluminum powder would work better than aluminum flakes. I think you can get powdered aluminum from chem supplies online.

Thenwcp (author)Pazzerz2009-08-09
or for small quantities

keep in mind powdered aluminum is pretty dangerous, especially since you will be pouring it near an open flame...the powder tends to explode when it gets into the the air and is exposed to flame.

galaxyman7 (author)Thenwcp2009-08-09

Ya I know. That is why you only grind it in a blender, so that is doesn't actually become powder, but more like granules. Aluminum powder would probably be a bad idea.

galaxyman7 (author)Pazzerz2009-05-29

You might try aluminum powder, but I think flakes actually increase strength more. Kind of like the rocks in concrete. But be my guest, I heard once that someone used aluminum powder instead of graphite powder, so that might be something to look into.

Pazzerz (author)galaxyman72009-05-29

Or how about this: steel wool, about 1/2 to 1" long fibers, in place of the aluminum (unless you can find aluminum wool). Another thought is the aluminum screening for doors and windows for pieces that are flat. I suppose it could be bent into shape to match a mould before pouring.

galaxyman7 (author)Pazzerz2009-05-29

That's a great idea. Fibers would give it a ton more strength and window screen is probably the best bet. Thanks, I will try that out.

123456789pos (author)2009-07-24

does the plastic react to water?

galaxyman7 (author)123456789pos2009-07-25

no it doesn't. By the way I really reccomend fiberglass cloth or something to reinforce it. Plain sulfur and graphite isn't really that strong. Use rocks or aluminum as an aggregate.

galaxyman7 (author)galaxyman72009-07-25

it doesnt soak up water either

Biopyro (author)2009-05-30

Excellent. I can't believe I haven't heard of this before!

galaxyman7 (author)2009-05-29

Just posted some pics of new castings I just did. They turned out really well. I am going to upload the video of me making them to youtube.

Tool Using Animal (author)2009-05-28

Interesting, honestly I was gonna call BS, but found this reference.

Questions, is it stable? Does it smell like sulfur? Does it shrink much?

For a short while, sulfur was used in woodworking inlay. It's stable enough to last centuries : )

Interesting, I as curious because we did a project in Junior High were we quenched molten sulfur to make plastic sulfur, which over time reverted to powdered sulfur. I guess slow cooling forms a different stable structure.

I was looking in Wikipedia, and a quick cooling of sulfur creates a flexible, helical crystal structure that changes to a more stable one over a short period of time. The PopSci article mentions that the sulfur turns white over time (100 years).

PKM (author)Tool Using Animal2009-05-28

DItto those questions, and also- is it brittle? Is it particularly elastic, or bendable when cold? How fine detail can you cast with it?

Nice link by the way, I haven't ever seen any evidence of this stuff working, so I tried it myself. This plastic is basically the same thing, except it has more graphite and aluminum mixed in. I will try to post a video of me cooking the stuff, once I get my video camera to work.

It does smell like sulfur if you put it up to your nose, but it doesn't smell if you don't. It shrinks to about half the volume of the powder, and yes, it is stable. I have a piece of the plastic I have kept around for a month, and it is still the same. Just make sure when you cook it not to heat it up too much. I tried using my toaster oven, and man did it smoke. It gives off SO2 if you heat it too much, so try to just use the barbeque and heat it slowly. When it starts to liquify, keep it at that temperature.

galaxyman7 (author)2009-05-29

Also I noticed that if you don't pour it all at once, but you pour it over itself, it is much less strong because it has layers and air pockets inbetween, so try to get the plastic so that it is very liquid and when you pour, and pour in one spot until the whole mold fills up. Another solution, like I suggested in the "Pour it" part, would be to heat up the mold in an oven before pouring into it.

galaxyman7 (author)2009-05-29

Anyone planning to try it? Just wondering.

Building Books (author)2009-05-28

I concur with TUA. I've been trawling instructables RSS every day and every time I've found something interesting it turns out to be bad. Nice to see something going against the trends: More Questions: What happens when It comes in contact with a naked flame? If you overheat it does it start to burn? I ask these Qs because it appears you are using 66% of the ingredients of gunpowder (albeit in different consistencies).

Yes it does start to burn if you heat it a lot. This happened to me when I used a toaster oven. But when it does burn, it's not violent, in fact sometimes you don't even notice it is burning. Just don't use an oven or something that will get it that hot. The melting point of sulfur is 112.8 degrees Celcius, or 234 degrees farenheight, so keep it at around that temperature. It doesn't do anything different if you heat it over open flame, in fact I use my barbeque to make it. Just make sure you heat slowly and evenly so you get a nice consistency. I know that sulfur is used in gunpowder, but alone it isn't dangerous. It smells bad, but it's not dangerous :)

hominid (author)galaxyman72009-05-29

Hi, while a bit noxious to those without asthma, it can however generate SO2 when burning and cause a MAJOR asthma attack in asthmatics and even in some non asthmatics. That is my only warning except in the molten state the plastic adheres tenaciously to skin and causes deep ulceration. Pain +++ :(

galaxyman7 (author)hominid2009-05-29

Yep, that's why I said not to burn it. I have breathed the SO2 and man does that stuff make you cough.

galaxyman7 (author)galaxyman72009-05-29

I have gotten the molten plastic on me, but because it cools so fast, the only danger to you would be if you dunked your hand in the pot with it.

Gorfram (author)Building Books2009-05-28

Re gunpowder, I might be worried if there were something nitrogen-rich in the mix, but there isn't. I mean, 50% of the ingredients of table salt is super-lethal chlorine gas, but all salt does is make you retain water :)

Building Books (author)Gorfram2009-05-29

and diamonds are just fancy lumps of charcoal, sulphuric acid is just water with some oxidized sulphur in it... Oh, and aluminium can be used as rocket fuel. Everything is -simply- something else but in certain situations, some things can combine and become volatile.

Gorfram (author)2009-05-29

Cool, G-man :)

I'd love to know what led you to come up with this. Were you just sitting there one day, eating pork rinds and watching re-runs of "Cops," when it suddenly struck you that you should melt industrial quantities of sulfur & graphite together, add shredded aluminum, and pour the result into molds?

After some moderate Google-based bush-whacking (would that be Google-whacking?), I've yet to find anything else on a plastic-type material made from sulfur & graphite (or sulfur & any other form of carbon). But I did steal a few sulfur-related notes from Wikipedia:

“Sulfur” seems to be preferred by the hard-core chemical nomenclatural brass hats, outside of that it seems to be like Channukah vs. Hannakuh: you chave a hoice.

Sulfur itself is odorless. The "smell of sulfur" is either from hydrogen sulfide (like from rotten eggs), or the sulfur dioxide created by burning sulfur (like from burnt matches). Small amounts of odor, due to slow oxidation in the presence of air, will come off of elemental sulfur.

Danger, Will Robinson:
Sulfur dioxide at high concentrations reacts with moisture to form sulfurous acid which may harm the lungs, eyes or other tissues. (Not Good.)

Hydrogen sulfide is toxic. Although very pungent at first, it quickly deadens the sense of smell, so victims may be unaware of its presence until death or other symptoms occur. (Yikes!)

Your process doesn't seem to produce either of these in very worrisome quantities, as long as all heating & casting operations are done outside.

galaxyman7 (author)Gorfram2009-05-29

Yep, just take lots of precautions and make sure you are OUTSIDE when you make this. If you make it right and don't burn the sulfur, it doesn't smell very bad at all.

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More by galaxyman7:Adding more extruders to any 3d printerMake a night time orthodontic retainerHow to make super cheap strong castable SULPHO-PLASTIC
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