This is a quick and simple method for making your own general-purpose plastic. The constituent ingredients are milk and vinegar. That's it. The total cost is less than $10, possibly less than $5 if you can get a good deal.

The plastic is moldable, and has a consistency of soggy cheese (I certainly hope I never encounter cheese that's anything like this!). When all is said and done, it should take you about 10-15 minutes to make the plastic (less if you make a small amount), 10 minutes of cleanup, plus 2+ days to allow the plastic to dry. As always, your milage may vary.

As for the final product's strength and whatnot, I would classify it as "okay." If you roll it thin (as I did in this instructable), it can easily be snapped in half, though it will probably survive a small drop on to carpet. Thicker pieces seem to be more resilient against average abuses - no problem dropping on to carpet, and if it's thick enough, you wouldn't be able to snap it in half. A blow from a hammer or other such object would quickly shatter it, though.

All in all, I would say this is mostly useful for folks looking for a fast and dirt cheap alternative to much better products available to the average joe. It's definitely not for something that will be handled on a daily basis - good enough for light decor, not much else.

This is my first Instructable, so bear with. Constructive criticism is always welcome!
 
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Step 1: Ingredients & Utensils

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This doesn't require anything fancy.

Essential Items:
Milk
Vinegar
Large Pot
Larger Pot (needs to be the same size as the other, or larger).
Spoon, preferably plastic or metal
Strainer or Colander, the finer the better
Stove or other item with which to simmer milk.
Paper Towels, lots and lots of paper towels

Handy, but not necessarily essential, items:
Wax Paper (good for rolling and shaping on. Water and other liquids bead up on it for easy clean-up; also non-stick with the casein)
Aluminum Foil (good for certain types of molds)
Rolling pin (if you're going to make a flat sheet of plastic)

Before you begin making the plastic, it's important to know what you're intending to make. By knowing what you're final goal is, you can make the preparations for the mold before you have a sloppy wad of plastic on your counter.

For this Instructable, I am making a curved piece that will fit on the front bezel of my computer case. Since this is beyond the scope of this particular instructable, I'm going to gloss over what I'm using. My mold is going to be the front bezel of the computer case, covered with aluminum foil. The plastic will dry nicely on top of it, and the aluminum won't shrivel or wrinkle when it gets wet as the plastic cures.

How much milk and vinegar will you need? The basic ratio that I follow is 1 TBSP of vinegar for every cup of milk. (16:1 ratio, milk to vinegar)

1 cup of milk will produce a puck of plastic about 2" in diameter, 1/8" thick.

To cover my case bezel, which is about 6 inches wide and 8 inches tall, I am going to use 8 cups of milk (and therefore 8 Tbsp of vinegar).
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ihaveguitarskills! says: Jan 8, 2013. 6:45 PM
Does it stink? and could it be made to replace plastic pellet gun pieces, if the previous were plastic too?
sudanione says: Aug 3, 2011. 7:29 PM
how can make it transparent
tbh-1138 says: Dec 12, 2012. 3:28 PM
You can't.
fretted says: Nov 30, 2012. 10:56 AM
Make Your Own Casein Glue from Milk
1. Heat some skimmed milk (do not let it boil)
2. Add about 3 teaspoons of vinegar (an acid) to the milk and stir slowly until the milk
separates into curds (solid sticky bits) and whey (clear liquid)
3. Pour the curds and whey through a tea strainer or sieve to collect the curds
4. In a container, add a little bit of bicarbonate of soda or milk of magnesia (alkali)
5. You should now have a sticky white substance called casein (milk protein). This can
be used as a binder in paint – just add some pigment!
karthikvasudevan says: May 26, 2012. 9:13 AM
What you've made right there is what we in India call 'paneer' we use it in curries n stuff its delicious, its a kind of cheese, and i'm not sure its a plastic.
bodeddie says: Nov 17, 2012. 9:36 AM
You are right that what he has made is Paneer. (Here in the states it is called Cottage Cheese.) However, do a google search for Casein Plastic and you will find that it was a widely used plastic for making buttons, knitting needles, ink pen cases etc. in the early 20th century. It is a polymer by definition and therefore technically a plastic. When used in manufacturing, it would be treated with formalin to retard an bio-degradation. Casein was also a widely used medium for paint.
fqian yan says: Mar 18, 2012. 2:34 AM
will mold grow on it in the process of drying?
billraymond says: Feb 18, 2012. 9:34 PM
Are you sure this is truly casein?? My understanding is that casein is precipitated from milk by rennet, not heat. Heating whey with vinegar or other acidifier creates ricotta, which is not a cheese, as it contains no casein, but is rather the precipitated albumin and other (not casein) proteins. Galalith is made from casein and must be fixed in a formaldehyde bath; it is not moldable.
CamoBedding says: Dec 4, 2011. 11:32 AM
I had no idea you could make home made plastic.
Banthablaster says: Dec 3, 2011. 1:35 PM
Is the Formaldehyde + Milk Galalith plastic brittle? can it keep a sharp point? will it bend? i will definitely experiment with casien

Any other chemistry suggestions would be welcome.
skooterv2 says: Jan 14, 2009. 1:56 PM
I play airsoft a lot and I play with some people with guns that hurt pretty bad...and this may sound weird but I was wondering if I made this thick enough do U think it could withstand some pretty hard blows like from guns shooting at 400+ fps... TYVM
Banthablaster says: Dec 3, 2011. 1:21 PM
Cool Idea, But how much milk are you willing to spend on this?

Imagine, an army of Cheese-weilding warriors!
drawe21 says: Mar 9, 2009. 9:29 PM
Use the Cornstarch, water, and oil plastic its hard and not too brittle
http://www.instructables.com/id/Easy_Biodegradable_Plastic/
brandon borick says: Feb 12, 2009. 10:41 PM
make a thin sheet then cover the back with glue and fabric
Coffeebot (author) says: Jan 14, 2009. 3:47 PM
It might work, if you make it thick enough. It's pretty brittle in thinner layers, and as such, wouldn't do well as body armor.

As for "making it stronger" (your note below), you could possibly add some fabric, of some sort to strengthen it.
skooterv2 says: Jan 15, 2009. 1:43 PM
Thank you.I really appreciate u getting back to me so quickly. How would u suggest adding fabric to it? Like just adding it in randomly when molding or what? Sorry I have no idea about that. Thanks again
Coffeebot (author) says: Jan 15, 2009. 8:08 PM
Not "randomly" but yes, while you mold it. Probably sandwiching the fabric between two layers of casein would work You'll need something fairly porous -- much looser than cheesecloth, I think. The reason is because of the thick, chunky consistency of the casein, you'll need a lot of gaps between threads in order for two sides to join together.
skooterv2 says: Jan 17, 2009. 2:49 PM
sorry another question if u don't mind. The juice that drains out of the casein and into a large pot, can u stir it and make that into plastic, too?
skooterv2 says: Jan 16, 2009. 5:30 AM
thank you And one last question if u don't mind. How thick would you recommend making it? Obviously you have more experience with casein then me. Tyvm again.
skooterv2 says: Jan 14, 2009. 2:04 PM
btw is there anything I could add to make it stronger?? And if u could e-mail me back on this I would greatly appreciate it
cd41 says: Jan 14, 2009. 4:29 PM
well this maybe the dumbest thing i ever suggested but you could try putting pencil lead(graphite) in it it is carbon and they add carbon to steel to make it harder and fabric or something but thats just what i would try
tbh-1138 says: Dec 12, 2012. 3:27 PM
Steel is iron alloyed with carbon. Putting pencil lead in casein would be like putting pieces of steel in lead to make it harder. It won't be much better than it would without the graphite. Something like fabric or paper pulp could work, though, and I don't think it would set any faster. Fibers make things stronger.
Banthablaster says: Dec 3, 2011. 1:16 PM
I want to use casien to make a DIY arrowpoint. I fear that Casien plastic will be

far, far too brittle. is this true?
TheLodgeShop says: Nov 21, 2011. 3:53 PM
wow very interesting.
Jaspreet kaur says: Oct 11, 2011. 6:49 AM
It is very interesting to make plastic out of milk.
But what are the advantages of extracted plastic?????
Although it contains caesin, would it cause any harm if someone eats it??????
Please do reply as soon as possible......
valleycrosser says: Feb 26, 2011. 9:50 AM
This is cheese. Period. Fromage. Queso. Formaggio. Cheese.
Broom says: Jul 22, 2011. 9:36 AM
Ah-yup. And while it is plastic by nature, a much superior plastic (harder, more resilient to shock, more resistant to mold) can be made by "dissolving" styrofoam in acetone.
bpfh says: Sep 25, 2011. 1:15 PM
This is relevant to my interests. Please explain more :)

Just dissolve the styrofoam (polystyrene?) in acetone to a thick goo, mold and leave to dry in a remote area as not to get her indoors all worked up about the acetone smell?
Broom says: Sep 26, 2011. 8:14 AM
Pretty much, bpfh. It's a weird, fun process: the acetone "eats" up the styrofoam like a hungry monster, turning a huge amount into a small "sediment" of sticky plastic.

It can take days & days for it to dry on its own, and of course it gives off acetone fumes the whole time. There's no chemical reaction - the acetone just dissolves the styrene in the the mostly-air styrofoam (emphasis on "foam"!), and then gets trapped inside the drying skin of the finished plastic if it's thick, slowing down the drying.

It shrinks somewhat in the drying process, but never (IME) breaks. Also, it seems to change if left in the acetone for a long time, becoming resistant to shape change, so it's best to mold it immediately after dissolving the styrene.
Broom says: Sep 26, 2011. 8:17 AM
BTW, an entire styrofoam cooler can be dissolved into about a pint of styrene, if you want an idea of how much contraction goes on in the "eating" portion! Don't have any stats on the drying shrinkage, but it's more like 1-15%... something reasonable.
bpfh says: Sep 27, 2011. 2:59 AM
Thanks for this update! I may try this in the next few weeks!

My project is quite simple: I have a motorbike where you cannot really get any plastic parts for it anywhere for love or money, and I need new wingmirror shells.

So either you are very very very lottery jackpot winning lucky if you find a part on ebay, or you cast it yourself.... I was originally thinking about resin casting, but resin costs a fortune. Casein seemed a good idea but being organic , I'm not sure about resistance to mold and fungus, and styrene seems easy enough to make... even if it may be more fragile than standard ABS plastic, I'm not very worried. You just need a ton of styrofoam to get a handful of goo :)

The other alternatives, like Sugru cost too much to be cost effective, and low temperature thermoplastics could melt if being left in the sun too long, so this method could allow me to make my prototype mirrors !

Cheers,
Daniel

achris4321 says: Sep 16, 2011. 5:10 AM
I am trying to learn how to make a case out of plastic so i need plastic so this was good.
gogglecrab says: Sep 7, 2011. 2:33 PM
what kind of mold would be the best for this plastic?
sudanione says: Aug 3, 2011. 7:18 PM
can this act as greenhouse cover..................................if the answer is no how can i construct green cover at home
khampton2 says: Aug 20, 2011. 12:44 PM
http://www.buffalo-niagaragardening.com/2011/03/22/5-great-tips-for-starting-new-plants-from-cuttings/
k_cat says: Jun 17, 2011. 4:56 PM
I wonder how I could turn the casein into knitting needles. Roll it and sand it down afterwards? Or use a tube or a straw as a mold?
Coffeebot (author) says: Jun 17, 2011. 10:08 PM
An interesting idea -- either might work, but the casein is pretty brittle and might break while you're knitting.

Don't forget that needles have specific sizes; hand rolling, or using a straw might not create a standard size.
k_cat says: Jun 18, 2011. 3:11 AM
I've made needles out of wood before, especially out of dowels which come in various metric sizes. I've seen plastic tubes with a certain diameter on the inside... I wouldn't make knitting needles with a diameter of under 3mm - maybe 4mm or 5mm would be the smallest possible size before they break.
But I think most knitting needles were made out of galalithe - and I'm not really sure I want to use formaldehyde. Hmmmmmmmmmm. On the other hand, casein needles might even break when I'm carefully sanding them down.

Another question, I'm sorry... ;-) Any idea on how to turn the casein into a spinnable fibre?
callmeshane says: Dec 9, 2008. 1:45 AM

Actually this is exactly the same as making tofu, from soya bean curd.

Citric acid - in powder form is cheap - especially in bulk.

Don't know about the casein content of soya bean flour...

Might be an idea to use skim milk powder as the fat free casein might be a better product.

Just curious - not that chemically ofay myself, but one would think that modifying the protein with HEAT and or other chemicals may have been done... just looked up.

http://books.google.com.au/books?id=0g9QjxsbqmUC&pg=PA136&lpg=PA136&dq=casien+plastic+heat+chemical&source=web&ots=u7KLwl6eWg&sig=9V40234r-SgMztftGpwzPYDrQgI&hl=en&sa=X&oi=book_result&resnum=1&ct=result

http://209.85.173.132/search?q=cache:SLP_f4OuT7QJ:www.umanitoba.ca/outreach/crystal/resources%2520for%2520teachers/Polymerization%2520-%2520Christy%2520Boettcher%2520%26.doc+casien+plastic+heat+chemical&hl=en&ct=clnk&cd=3&gl=au

http://chestofbooks.com/home-improvement/repairs/painting/Paint-Making-Color-Grinding/Part-V-Casein-And-Cold-Water-Paints-Chapter-XXXI-Origin-A.html

http://www.plastics-china.com/Raw_Material.htm

Casein Formaldehyde (Lactoid, Erinoid, Galalith)

Invented at the turn of the century, manufacture was based on fat-free milk to which resin was added to form curds which, when suitably dried, processed and coloured, could be extruded into rods and made into sheets. The material was then hardened in a bath of formaldehyde from whence it was machined into the desired end use. The brilliant colours and patterns made casein a leading material for making products such as buttons, buckles, fountain pen, barrels and knitting needles.

http://museo.cannon.com/museo/inglese/eplasti.htm

# Casein formaldehyde

Casein formaldehyde is a plastic of natural protein origin made from organic substances such as milk, horn or vegetable products such as soy beans, wheat and the like. It was obtained in 1897 by Adolph Spitteler and W.Kirsche who started out with whey and formaldehyde and tested the action of an enzyme on them. The patent was registered in Baviera and then extended to the USA, Great Britain and Italy. It should be noted that with its commercial name, Galalith (Galalite in Italy and Erinoid in Great Britain) it sometimes looked like celluloid, sometimes ivory and sometimes artificial horn. The first factory to manufacture it was in Great Britain in 1913. In 1930 world-wide production had reached 10,000 tons. Casein formaldehyde was used to make buttons, pins, cigarette-cases, fountain pens, umbrella handles and radio cabinets.
gtoal says: Jan 5, 2011. 2:11 PM
Casein-formaldehyde - also known as "French Bakelite" (not to be confused with 'Fake Bakelite' which is becoming a problem in the antiques world...). Bakelite is an interesting substance too but I think because of the pressure vessel needed, probably not a home project. People interested in this area should have a look at the Oogoo instructable as well.
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